JP2015158641A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a rotation stop position of a drive coupling on a body side, which drives a driven body in developing means, only when necessary, thereby eliminating unnecessary latency.SOLUTION: An image forming apparatus has toner discharge mode which discharges toner in toner supply means. In the toner discharge mode, driving means of a drive coupling 87 is controlled by a controller, to stop the drive coupling 87 at a predetermined rotation stop position after the toner discharge mode. In non-toner discharge mode, the drive coupling 87 stops at a randomly selected rotation stop position quickly.

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, various driven bodies for image formation are detachably attached to the main body of the image forming apparatus. This facilitates inspection of the driven body and replacement at the time of deterioration or failure.

  Examples of the driven body include an image forming unit and a toner supply container for supplying toner as a developer to the image forming unit. The image forming unit includes a plurality of rotating members such as an image carrier, a developing roller, and a toner conveying screw. These rotating members are driven by driving means on the main body side.

  The toner supply container is normally used in the form of a toner bottle, and the toner bottle is mounted on the main body in a horizontal and horizontal state and rotated. A helical shape is formed on the inner peripheral surface of the toner bottle, and the toner inside is moved in the direction of the outlet of the toner bottle by the rotation of the toner bottle.

  On the other hand, in a color image forming apparatus, image forming units of at least four colors (YMCBk) of yellow, magenta, cyan, and black are used. In recent years, color image forming apparatuses have developed so-called “special color creation” such as light-colored toner (for example, light cyan and light yellow) and highly transparent toner (for example, transparent toner) in addition to the YMCBk image forming unit. "Image unit" may be used (for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-171498) and Patent Document 2 (Japanese Patent Laid-Open No. 2007-316313)). The special color image forming unit is selectively used according to the printing application such as image quality improvement, glossiness improvement or color reproducibility improvement.

  When adding one special color image forming unit in a tandem color image forming apparatus using an intermediate transfer belt, a fifth station is provided after the first to fourth stations on which the YMCBk image forming unit is mounted (hereinafter referred to as “station”). "Is written as" St "). The spot color image forming unit attached to the fifth St is often replaced with another spot color image forming unit depending on the printing application, and the replacement frequency is higher than the replacement frequency of the YMCBk four-color image forming unit.

  Transmission of driving force between the main body of the image forming apparatus and the driven body is generally performed by coupling. This coupling includes an axial coupling that is engaged from the axial direction and a perpendicular coupling that is engaged from a direction perpendicular to the axial direction. In any coupling method, if the rotational positions of the drive side and the passive side do not match when the coupling is engaged, the couplings interfere with each other and cannot be engaged well, and the drive force cannot be transmitted. .

  For example, as described in Patent Document 3 (Japanese Patent Laid-Open No. 2007-304173, FIGS. 11 and 12), the axial coupling includes a drive coupling having a connection concave portion having a triangular cross section and a connection convex portion having a triangular cross section. Some have passive couplings. By inserting the passive coupling into the drive coupling from the axial direction and engaging both the couplings, it is possible to transmit the driving force in an aligned state in which both the couplings are aligned with the axis of the rotating shaft.

  In the axial coupling, even if the rotational position of the coupling is shifted when the driven body is mounted, the rotational position matches when the drive coupling is slightly rotated. Then, one coupling moves forward and engages with the other coupling by the force of the spring, and the driving force can be transmitted.

  However, depending on how the driven body is mounted, the couplings may collide with each other without being engaged well, and the coupling may be damaged or broken. Therefore, it is conceivable to form tapered portions on the front end sides of both couplings as an interference avoidance mechanism for avoiding such interference, which are in sliding contact with each other when the coupling is engaged. By this taper portion, the shift of the rotational position of the coupling is corrected when the passive coupling is inserted in the axial direction.

  Some perpendicular couplings are provided with an interference avoidance mechanism different from the above in order to align the rotational positions of both couplings. For example, in Patent Document 4 (Japanese Patent Laid-Open No. 4-240870), a gear provided on a driven shaft of an image forming unit is engaged with a fixed linear gear provided on the main body side immediately before coupling engagement. ing. In this way, the driven shaft is rotated to a predetermined rotational position and then engaged with the drive coupling on the main body side.

  When a coupling such as that disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2007-304173, FIGS. 11 and 12) is used, the passive coupling is strong against the driving coupling depending on how the image forming unit as the driven body is mounted. collide. If the coupling is damaged by this collision, the rotational driving force cannot be transmitted.

  Further, if the coupling is not broken, even if the rotational driving force can be transmitted, the alignment operation is impaired even if the rotational driving force can be transmitted. As a result, the rotation of the image carrier and the developing roller may be uneven and image quality abnormality may occur. . In addition, if an interference avoidance mechanism using a tapered portion is provided, the coupling becomes large and the cost is increased, and the degree of freedom in design is restricted.

  Further, when an interference avoidance mechanism such as that disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 4-240870) is provided, the apparatus becomes large due to the installation space of the gear, and the cost increases due to an increase in the number of parts.

  In addition, with both coupling methods of axial coupling and right angle coupling, it is also possible to smoothly remove and attach the passive coupling to the drive coupling by always controlling the rotation stop position of the drive coupling to be constant. (Patent Document 5 (Japanese Patent Laid-Open No. 2005-292676, [0008] stage)).

  However, when this is done, the waiting time until the stop control is completed becomes longer than when the stop control is not performed. In particular, when the driven body is removed and inspected, and the driven body is remounted without any abnormality, the rotational positions of the coupling on the driving side and the passive side at the time of remounting are the same as when the driven body is removed. Not changed. Therefore, since it can be remounted without rotation stop position control, a wasteful waiting time occurs. Therefore, there is a problem that workability is not always good.

  Therefore, an object of the present invention is to eliminate unnecessary waiting time by performing rotation stop position control of the drive coupling on the main body side that drives the driven member of the developing means only when necessary.

In order to solve the above problems, the present invention provides:
An electrophotographic image forming apparatus, wherein the image forming apparatus includes:
A drive coupling disposed in the main body of the image forming apparatus;
Drive means for rotating the drive coupling;
A controller for controlling the driving means;
A developing means having at least one driven member, and detachable from the main body of the image forming apparatus;
A passive coupling coupled to the driven body;
Toner replenishing means for replenishing toner as developer to the developing means,
In the image forming apparatus, when the developing unit is attached to the main body of the image forming apparatus, the passive coupling engages with the drive coupling, and the driven member is driven by the driving unit.
The image forming apparatus has a toner discharge mode for discharging the toner in the toner replenishing means, and in the toner discharge mode, the drive is performed so that the drive coupling stops at a predetermined rotation stop position. Means are controlled by the controller; and
In the non-toner discharge mode other than the toner discharge mode, when the drive coupling is rotating, the drive means is controlled by the controller so that the drive coupling quickly stops at an arbitrary rotation stop position. An image forming apparatus.

  According to the present invention, in the toner discharge mode in which replacement with a different developing unit is highly possible, the rotation of the driving coupling on the main body side and the passive coupling on the developing means are stopped by controlling the rotation stop position of the driving means on the main body side. Position alignment can be performed.

  Therefore, the couplings can be smoothly engaged with each other when different developing means are mounted. Further, the alignment of the rotation stop position eliminates the need for an interference avoidance mechanism for drive coupling and passive coupling, thereby reducing the cost and space of the image forming apparatus.

  On the other hand, in the non-toner discharge mode in which there is a high possibility that the same developing means will be remounted, the rotation stop position control of the drive coupling on the main body side is not performed, so the waiting time can be shortened.

1 is a schematic diagram of an image forming apparatus. It is the schematic of an image formation unit. It is a perspective view which shows a developing unit. FIG. 6 is a plan view showing a toner conveying screw inside the developing unit. It is a perspective view showing a toner conveying screw. 2 is a perspective view of a drive coupling disposed on the main body side of the image forming apparatus. FIG. It is an expansion perspective view of a drive coupling. (A) is a front view of a drive coupling, (b) is a front view of a passive coupling on the process unit side. FIG. 3 is a schematic view of a toner supply mechanism from a toner bottle to a developing unit. It is a figure of an operation panel. 2 is a block diagram of a controller of the image forming apparatus. FIG. FIG. 6 is a flowchart showing a spot color toner replacement operation. FIG. 6 is a flowchart illustrating an operation in a toner discharge mode. FIG. 7 is a flowchart up to home position stop control of a developing motor in a toner discharge mode. It is a flowchart which shows the home position stop control of a developing motor.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. In each drawing for explaining this embodiment, constituent elements such as members and components having the same function or shape are given the same reference numerals as much as possible to distinguish them, and then the explanation will be given. Is omitted.

(Overall configuration of image forming apparatus)
FIG. 1 schematically shows an embodiment of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a color laser printer that can form a color image. The image forming apparatus 100 may be an electrophotographic image forming apparatus such as another type of printer, facsimile, copying machine, or a combination of these.

  The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. The image forming apparatus 100 can form an image using plain paper generally used for copying, OHP sheets, thick paper such as cards and postcards, and envelopes as sheet-like recording media. .

  The image forming apparatus 100 includes photosensitive drums 20Y, 20C, 20M, and 20Bk as image carriers that can form images as images corresponding to colors separated into yellow, magenta, cyan, black, and special colors. The tandem structure (tandem system) with 20S arranged side by side is adopted. Y, C, M, Bk, and S added after the numerals of the respective symbols indicate yellow, cyan, magenta, black, and special color members.

  The photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are on the outer peripheral surface side of the intermediate transfer belt 11 as an intermediate transfer member that is an endless belt disposed in the substantially central portion of the main body 99 of the image forming apparatus 100. That is, it is located on the image forming surface side.

  The intermediate transfer belt 11 is movable in the direction of the arrow A1 in FIG. 2 while facing the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S. The photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are arranged in this order from the upstream side in the A1 direction.

  Visible images, that is, toner images formed on the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are respectively superimposed and transferred to the intermediate transfer belt 11 that moves in the direction of the arrow A1, and then transfer paper that is a recording medium. The images are transferred to S in a batch. Therefore, the image forming apparatus 100 is an intermediate transfer type image forming apparatus.

  The lower portion of the intermediate transfer belt 11 faces the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S, and the opposed portions correspond to the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S. A transfer portion 98 for transferring the upper toner image to the intermediate transfer belt 11 is formed.

  In the superimposing transfer with respect to the intermediate transfer belt 11, the toner images formed on the respective photoconductive drums 20Y, 20C, 20M, 20Bk, and 20S are moved to the same position on the intermediate transfer belt 11 in the process of moving the intermediate transfer belt 11 in the A1 direction. Is transferred to Primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S are disposed at positions facing the respective photoconductive drums 20Y, 20C, 20M, 20Bk, and 20S with the intermediate transfer belt 11 interposed therebetween. By the voltage application by these primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S, the superimposed transfer is performed with the timing shifted from the upstream side in the A1 direction toward the downstream side.

  The intermediate transfer belt 11 has a multilayer structure in which the base layer is made of a material with less elongation, the surface of the base layer is covered with a material having good smoothness, and the coat layer is formed on the base layer. . Examples of the material of the base layer include a fluororesin, a PVD sheet, and a polyimide resin. Examples of the material of the coat layer include a fluorine resin.

  The intermediate transfer belt 11 has a detent guide (not shown) as a detent member at each edge portion thereof. The offset guide is provided to prevent the intermediate transfer belt 11 from being biased in any direction perpendicular to the paper surface in FIG. 1 when the intermediate transfer belt 11 rotates in the A1 direction. The stopper guide is made of urethane rubber, but can be made of various rubber materials such as silicon rubber.

  The photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are image forming units 60Y and 60C, which are toner image forming units as image forming units, for forming yellow, cyan, magenta, black, and special color images, respectively. , 60M, 60Bk, 60S.

  The image forming apparatus 100 includes five image forming units 60Y, 60C, 60M, 60Bk, and 60S, and the transfer belt unit 10. The transfer belt unit 10 includes an intermediate transfer belt 11 and is disposed so as to face the upper portions of the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S.

  A secondary transfer roller 5 is disposed at one end of the transfer belt unit 10 so as to face the intermediate transfer belt 11 and serves as a transfer member that rotates along with the intermediate transfer belt 11. In addition, an optical scanning device 8 as a writing unit is disposed below the image forming units 60Y, 60C, 60M, 60Bk, and 60S.

  Below the optical scanning device 8, a sheet feeding device 61 as a paper feeding cassette on which the transfer paper S is stacked is disposed. In front of the sheet feeding device 61, a feeding roller 3, a timing roller pair 4, and a sensor (not shown) that detects that the leading edge of the transfer sheet S has reached the timing roller pair 4 are disposed.

  Then, the transfer sheet S conveyed from the sheet feeding device 61 is secondarily transferred from the timing roller pair 4 at a predetermined timing in accordance with the toner image formation timing by the image forming units 60Y, 60C, 60M, 60Bk, and 60S. It feeds out toward the transfer unit 90.

  The image forming apparatus 100 also includes a fixing device 6 as a roller fixing type fixing unit for fixing the toner image onto the transfer paper S to which the toner image is transferred, and the fixed transfer paper S outside the main body 99. A paper discharge roller 7 is provided. Above the transfer belt unit 10, toner bottles 9Y, 9C, 9M serving as toner replenishing containers, which are filled with toners of yellow, cyan, magenta, black, and special colors as developers and are attached to and detached from the main body 99, are provided. 9Bk and 9S are provided.

  A paper discharge tray 17 is disposed on the upper side of the main body 99, and the transfer paper S discharged to the outside of the main body 99 by the discharge roller 7 is stacked on the paper discharge tray 17. Unnecessary items such as waste toner are stored in a waste toner tank 83.

  The image forming apparatus 100 also includes a toner supply mechanism 80 as a toner replenishing unit, as shown in FIGS. 3A and 5. The toner supply mechanism 80 includes developing units 50Y, 50C, 50M, and 60N, which are respectively provided in the image forming units 60Y, 60C, 60M, 60Bk, and 60S with toner in the toner bottles 9Y, 9C, 9M, 9Bk, and 9S. Supply to 50Bk, 50S.

  The image forming apparatus 100 also includes an operation panel 160 (see FIG. 6 described later) as an input unit for performing various settings for the image forming apparatus 100, a CPU, a memory, and the like that control the operation of the entire image forming apparatus 100. And a controller 110 (see FIG. 7 described later).

  In addition to the intermediate transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S. The intermediate transfer belt 11 is wound around a driving roller 72 that is a driving member, a transfer inlet roller 73, and a cleaning counter roller 74. The cleaning counter roller 74 is urged by a spring 75 as an urging unit in a direction in which the tension of the intermediate transfer belt 11 is increased.

  The transfer belt unit 10 also has an intermediate transfer belt case 14 that forms the casing. The intermediate transfer belt case 14 is detachably supported with respect to the main body 99. A driving roller 72, a transfer inlet roller 73, a cleaning counter roller 74, and a spring 75 are held on the intermediate transfer belt case 14. A cleaning device 13 as an intermediate transfer belt cleaning device is disposed integrally with the intermediate transfer belt case 14. The cleaning device 13 is disposed opposite the intermediate transfer belt 11 and cleans the intermediate transfer belt 11.

  The transfer belt unit 10 also includes a drive system (not shown) that rotationally drives the drive roller 72, a power supply as a primary transfer bias application unit (not shown) that applies a primary transfer bias to the primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S. And a bias controller.

  The transfer entrance roller 73 and the cleaning counter roller 74 are driven rollers that rotate with the intermediate transfer belt 11 that is rotationally driven by the drive roller 72. The primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S press the intermediate transfer belt 11 from the back surface thereof toward the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S to form primary transfer nips.

  The primary transfer nip is formed in a portion of the intermediate transfer belt 11 that extends between the transfer entrance roller 73 and the cleaning counter roller 74. The transfer entrance roller 73 and the cleaning counter roller 74 have a function of stabilizing the primary transfer nip.

  In each primary transfer nip, a primary transfer electric field is formed between the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S and the primary transfer rollers 12Y, 12C, 12M, 12Bk, and 12S by the action of the primary transfer bias. . The toner images of the respective colors formed on the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are primarily transferred onto the intermediate transfer belt 11 due to the influence of the primary transfer electric field and nip pressure.

The driving roller 72 is in contact with the secondary transfer roller 5 via the intermediate transfer belt 11 to form a secondary transfer portion 90.
The cleaning counter roller 74 has a function as a tension roller as a pressure member that applies a predetermined tension suitable for transfer to the intermediate transfer belt 11 by the action of the spring 75.

  The cleaning device 13 is disposed to face the intermediate transfer belt 11 at a position on the left side of the cleaning facing roller 74 in FIG. Although not shown, the cleaning device 13 includes a cleaning brush and a cleaning blade disposed so as to face and contact the intermediate transfer belt 11. The intermediate transfer belt 11 is cleaned by scraping and removing foreign matters such as residual toner on the intermediate transfer belt 11 with a cleaning brush and a cleaning blade. Unnecessary items such as waste toner generated by this cleaning are stored in a waste toner tank 83 through a waste toner path (not shown).

  The sheet feeding device 61 is disposed at the lower part of the main body 99 and accommodates a plurality of transfer sheets S in a state of a stack of transfer sheets. The sheet feeding device 61 includes a feeding roller 3 as a paper feeding roller that contacts the upper surface of the uppermost transfer sheet S. The uppermost transfer sheet S is fed toward the timing roller pair 4 by rotating the feeding roller 3 counterclockwise.

  The timing roller pair 4 is precisely machined in outer diameter in order to match the image forming speed, in other words, the moving speed of the intermediate transfer belt 11 and the feeding speed. The accuracy is within 0.03 mm in outer diameter, for example.

  In the secondary transfer unit 90, a secondary transfer electric field is formed between the driving roller 72 and the intermediate transfer belt 11 and the secondary transfer roller 5 by the action of the secondary transfer bias. The toner image formed on the intermediate transfer belt 11 is secondarily transferred onto the transfer sheet S due to the influence of the secondary transfer electric field and nip pressure. The drive roller 72 also serves as a secondary transfer counter roller.

  The fixing device 6 includes a fixing roller 62 having a heat source therein, and a pressure roller 63 pressed against the fixing roller 62. Then, the transfer paper S carrying the toner image is passed through a fixing unit which is a pressure contact portion between the fixing roller 62 and the pressure roller 63, so that the carried toner image is applied to the surface of the transfer paper S by the action of heat and pressure. It has become established.

  The yellow, cyan, magenta, black, and special color toners in the toner bottles 9Y, 9C, 9M, 9Bk, and 9S are supplied to the developing unit 50Y by a predetermined replenishment amount by the toner supply mechanism 80 shown in FIGS. , 50C, 50M, 50Bk. The toner bottles 9Y, 9C, 9M, 9Bk, and 9S are consumables that are replaced when the toner in the interior is exhausted, and are removed from the main body 99 and replaced when the toner is exhausted.

  The cleaning device 13 and the cleaning counter roller 74 move downward together with the primary transfer rollers 12Y, 12C, 12M, and 12S when the black image is formed, and the intermediate transfer belt 11 is moved from the photosensitive drums 20Y, 20C, 20M, and 20S. It is comprised so that it may space apart.

  Various types of information input through the operation panel are recognized and identified by the controller 110. Examples of information that can be input through the operation panel include a reference value used when detecting the stay of the developer by a stay detection sensor (not shown). The operation panel has a display unit as output means for performing a predetermined display under the control of the controller 110.

  The configuration of the image forming units 60Y, 60C, 60M, 60Bk, and 60S will be described as a representative of the configuration of the image forming unit 60Y including the photosensitive drum 20Y. Since the configurations of the other image forming units 60C, 60M, 60Bk, and 60S are substantially the same, in the following description, for the sake of convenience, reference numerals corresponding to the reference numerals assigned to the configuration of the image forming unit 60Y are used. The other image forming units 60 </ b> C, 60 </ b> M, 60 </ b> Bk, and 60 </ b> S are also configured, and detailed description thereof is omitted as appropriate.

(Imaging unit)
As shown in FIG. 2, in the image forming unit 60Y including the photosensitive drum 20Y, various components including the primary transfer roller 12Y are disposed around the photosensitive drum 20Y. That is, along the rotation direction B1, which is the clockwise direction in FIG. 2, the primary transfer roller 12Y, the cleaning device 40Y as the cleaning unit, the charging unit 30Y as the charging unit as the charging unit, and the image forming unit as the developing unit A developing unit 50Y is provided.

  The charging device 30Y includes a charging roller 31Y that rotates passively in contact with the surface of the photosensitive drum 20Y, and a cleaning roller 32Y that rotates passively in contact with the charging roller 31Y. The charging roller 31Y is connected to a voltage application means (not shown) for applying a bias of an alternating current component to a direct current. As a result, in the charging region facing the photoconductor drum 20Y, the surface of the photoconductor drum 20Y is neutralized and at the same time charged to a predetermined polarity.

  The cleaning roller 32Y rotates passively around the charging roller 31Y to clean the charging roller 31Y. As described above, in this embodiment, the charging system using the contact roller is adopted. However, the charging system may be one using a proximity roller or one using a corotron system. .

  The developing unit 50Y has a developing roller 51Y disposed close to and facing the photosensitive drum 20Y. Then, in the developing area between the developing roller 51Y and the photosensitive drum 20Y, the yellow toner is electrostatically transferred to the electrostatic latent image formed on the surface of the photosensitive drum 20Y. Visualize as a yellow toner image. Details of the developing unit 50Y will be described later.

  A predetermined voltage suitable for primary transfer is applied to the primary transfer roller 12Y from a power source by a primary transfer bias applying unit based on control by a bias controller.

  As shown in FIG. 2, the optical scanning device 8 shown in FIG. 1 irradiates a light modulated laser beam L onto a region between the charged region and the developing region on the photosensitive drum 20Y. As a result, the surface of the photosensitive drum 20Y charged by the charging roller 31Y is exposed, the potential of the exposed portion is lowered to provide an electrostatic potential difference on the surface of the photosensitive drum 20Y, and the electrostatic latent image Form. Yellow toner is supplied and adhered to the portion where the potential is lowered by the developing unit 50Y, and a visible image is formed as a yellow toner image.

  The cleaning device 40Y includes a cleaning case 43Y having an opening at a portion facing the photoconductor drum 20Y. The cleaning case 43Y is provided with a cleaning roller 45Y that comes into contact with the photosensitive drum 20Y to scrape off and remove unnecessary toner, carrier, paper dust and the like on the photosensitive drum 20Y.

  A cleaning blade 41Y is disposed in the cleaning case 43Y. The cleaning blade 41Y comes into contact with the photosensitive drum 20Y at a position downstream of the cleaning roller 45Y in the rotation direction B1 of the photosensitive drum 20Y, and scrapes and cleans unnecessary materials on the photosensitive drum 20Y.

  The cleaning device 40Y also includes a discharge screw 42Y that is rotatably supported by the cleaning case 43Y. By the discharge screw 42Y, unnecessary materials such as waste toner scraped and removed by the cleaning roller 45Y and the cleaning blade 41Y are conveyed toward the waste toner tank 83. The discharge screw 42Y constitutes a part of a waste toner path (not shown).

  The image forming unit 60Y includes a photosensitive drum 20Y, a primary transfer roller 12Y, a cleaning device 40Y, a charging device 30Y, and a developing unit 50Y. A unit obtained by removing the primary transfer roller 12Y from the image forming unit 60Y constitutes a process unit 95Y.

  That is, the photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, and the developing unit 50Y constitute a process unit 95Y. The process unit 95Y is integrated, and is detachable from the main body 99 of the image forming apparatus 100 toward the front side of the sheet in FIG.

  Further, the photosensitive drum 20Y is detachable from the main body 99 of the image forming apparatus 100 to the front side of the sheet in FIG. 1 and is detachable. Further, the process unit 95Y excluding the photosensitive drum 20Y, that is, the cleaning device 40Y, the charging device 30Y, and the developing unit 50Y constitute a unit (hereinafter referred to as a developing unit). This developing unit is integrated, and is detachable from the main body 99 of the image forming apparatus 100 toward the front side of the sheet in FIG.

  Further, the developing unit 50Y is detachable from the main body 99 of the image forming apparatus 100 to the front side of the paper in FIG. Further, the process unit 95Y excluding the developing unit 50Y, that is, the photosensitive drum 20Y, the cleaning device 40Y, and the charging device 30Y constitute a unit. This unit is integrated, and is detachable from the main body 99 of the image forming apparatus 100 toward the front side in FIG.

(Basic operation of image forming apparatus)
In the image forming apparatus 100 having such a configuration, when a signal indicating that a color image should be formed is input, the driving roller 72 is driven, and the intermediate transfer belt 11, the transfer inlet roller 73, and the cleaning counter roller 74 are passively rotated. At the same time, the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S are rotationally driven in the B1 direction in FIG.

  The surface of the photosensitive drum 20Y is uniformly charged by the charging roller 31Y as it rotates in the B1 direction. Then, an electrostatic latent image corresponding to yellow is formed by exposure scanning of the laser beam L from the optical scanning device 8.

  This electrostatic latent image is developed with yellow toner by the developing unit 50Y. The toner image, which is a yellow single color image obtained by development, is primarily transferred to the intermediate transfer belt 11 moving in the A1 direction by the primary transfer roller 12Y. Unnecessary substances including toner remaining on the photosensitive drum 20Y after the transfer are satisfactorily removed by the cleaning device 40Y, and the cleaned photosensitive drum 20Y is subjected to the next charge removal and charging by the charging roller 31Y.

  Similarly, the toner images of the respective colors are formed on the other photosensitive drums 20C, 20M, 20Bk, and 20S, and the formed toner images that are single-color images of the respective colors are respectively transferred by the primary transfer rollers 12C, 12M, 12Bk, and 12S. Primary transfer is sequentially performed sequentially at the same position on the intermediate transfer belt 11 moving in the A1 direction. The toner image superimposed on the intermediate transfer belt 11 moves to the secondary transfer unit 90 that is opposed to the secondary transfer roller 5 as the intermediate transfer belt 11 rotates in the A1 direction. 2 is secondarily transferred to the transfer paper S.

  The transfer sheet S fed from the sheet feeding device 61 by the feeding roller 3 is conveyed between the intermediate transfer belt 11 and the secondary transfer roller 5 by the timing roller pair 4 at a predetermined timing. The predetermined timing is controlled based on a detection signal from a sensor that detects that the leading edge of the transfer sheet S has reached the timing roller pair 4 and the position of the toner image on the intermediate transfer belt 11.

  The transfer paper S enters the fixing device 6 when the toner images of all colors are transferred and carried. When the transfer sheet S passes through the fixing unit between the fixing roller 62 and the pressure roller 63, the carried toner image is fixed to the transfer sheet S by the action of heat and pressure, and the transfer sheet S is synthesized on the transfer sheet S. A color image which is a color image is fixed.

  The fixed transfer paper S that has passed through the fixing device 6 passes through the paper discharge roller 7 and is stacked on the paper discharge tray 17 at the top of the main body 99. On the other hand, the intermediate transfer belt 11 that has finished the secondary transfer is cleaned by a cleaning brush and a cleaning blade provided in the cleaning device 13 to prepare for the next charging step and developing step.

(Development unit and toner supply mechanism)
In such an image forming process, yellow, cyan, magenta, black, and special color toners are consumed in the developing units 50Y, 50C, 50M, 50Bk, and 50S, respectively. Therefore, a required amount of toner is supplied from the toner bottles 9Y, 9C, 9M, 9Bk, and 9S to each developing unit by the toner supply mechanism 80 shown in FIGS. 3A and 5 according to the amount of consumption. It has become so.

  The developing units 50Y, 50C, 50M, 50Bk, and 50S charge the toner of each color in order to develop the electrostatic latent images on the photosensitive drums 20Y, 20C, 20M, 20Bk, and 20S with the toner of each color. ing.

  The developing units 50Y, 50C, 50M, 50Bk, and 50S will be described as a representative of the configuration of the developing unit 50Y. Since the other developing units 50C, 50M, 50Bk, and 50S have substantially the same configuration, in the following description, the configuration of the developing unit 50Y will be described, and the other developing units 50C, 50M, 50Bk, The configuration of 50S is omitted.

  As shown in FIG. 2, in addition to the developing roller 51Y, the developing unit 50Y includes a developing case 55Y as a case that is a casing as a developer container having an opening at a portion facing the photosensitive drum 20Y, and a developing roller. A developing blade 52Y that regulates the developer on 51Y to a certain height.

  The developing unit 50Y is also disposed below the developing case 55Y so as to face each other, and a first toner conveying screw serving as a first conveying member, which is a conveying means, stirs while conveying the developer in a circulating manner. 53Y and a second toner conveying screw 54Y as a second conveying member as conveying means.

  The toner conveying screw 54Y rotates in the same direction in conjunction with the toner conveying screw 53Y by meshing between a rotating shaft 83Y and a gear (not shown) attached to the ends of the rotating shaft 84Y and an idle gear interposed between the two gears. It is supposed to be.

  The developing unit 50Y also includes a toner concentration detection sensor 92Y as a toner concentration detecting unit that detects the toner concentration contained in the developer in the developing case 55Y. In addition, a bias applying unit (not shown) for applying a developing bias of a DC component is included. The first toner conveying screw 53Y and the second toner conveying screw 54Y have driving means (not shown) that rotationally drives the same in the same direction.

  The developing unit 50Y performs development using a developer that is a two-component developer containing a yellow toner that is a non-magnetic toner and a carrier that is a magnetic material mainly composed of iron powder. The developer is accommodated in 55Y.

  The developing roller 51Y is disposed in close proximity to the photosensitive drum 20Y so as to face the photosensitive drum 20Y from the opening of the developing case 55Y. As shown in FIG. 2, the developing roller 51Y has a thin cylindrical developing sleeve 56Y made of aluminum which is a non-magnetic material that is rotatable and carries a developer on its surface. The developing sleeve 56Y includes a magnet 57Y that is fixedly disposed so as to be covered with the developing sleeve 56Y and generates a magnetic field for supporting the developer on the developing sleeve 56Y.

  As shown in FIG. 2, the developing case 55Y includes a developing chamber 58Y that stores the first toner transport screw 53Y and a stirring chamber 59Y that stores the second toner transport screw 54Y. The developing chamber 58Y and the stirring chamber 59Y are partitioned by a partition wall 81Y. The developing case 55Y has a supply port 91Y, and the supply port 91Y receives yellow toner from the toner bottle 9Y shown in FIG. 1 through the toner supply mechanism 80 shown in FIG. 3A.

  As shown in FIG. 2 or 3A, since the first toner conveying screw 53Y faces the developing roller 51Y so as to supply the developer to the developing roller 51Y, the developing chamber 58Y and the stirring chamber 59Y have a developing chamber. 58Y is located closer to the developing roller 51Y.

  In FIG. 3A and FIG. 3B, for convenience of explanation, the upper side of the developing case 55Y is illustrated as being open. However, actually, as shown in FIG. 2, the developing case 55Y is sealed inside so that the developer does not scatter outside, except for the opening where the developing roller 51Y faces the photosensitive drum 20Y. It has a configuration.

  As shown in FIG. 3B or 3C, the first toner transport screw 53Y and the second toner transport screw 54Y have a rotation shaft 83Y and a rotation shaft 84Y, respectively, which are the rotation centers. On these rotating shafts, a screw portion 85Y and a screw portion 86Y constituted by spiral ridges are formed.

  The screw part 85Y and the screw part 86Y have spiral shapes opposite to each other. The first toner transport screw 53Y and the second toner transport screw 54Y are disposed in parallel to each other and in parallel to the developing roller 51Y. The rotary shaft 83Y and the rotary shaft 84Y have gears (not shown) attached to their ends, and an idle gear is engaged between the two gears. Therefore, when one of the rotation shaft 83Y or the rotation shaft 84Y is rotated, the other is rotated in the same direction.

  The first toner transport screw 53Y and the second toner transport screw 54Y have their rotation shafts 83Y and 84Y rotated in the same direction by the drive means. The rotation about the rotation shaft 83Y and the rotation shaft 84Y causes the direction of the rotation axis, that is, the direction in which the rotation shaft 83Y and the rotation shaft 84Y extend (perpendicular to the paper surface in FIG. 2) by the action of the screw portion 85Y and the screw portion 86Y. Developer) in the right direction).

  More specifically, the developer transport direction by the first toner transport screw 53Y and the second toner transport screw 54Y will be described. The first toner transport screw 53Y is the rear side of the paper surface in FIG. 2 in the developing chamber 58Y. The developer is conveyed in a first direction corresponding to the left side in 3B. The second toner conveying screw 54Y conveys the developer in the second direction corresponding to the right side in FIG. 3B on the front side in FIG. 2 in the stirring chamber 59Y.

  The developing chamber 58Y and the agitating chamber 59Y are partitioned by a partition wall 81Y. Both ends of the partition wall 81Y have a gap between the inner surface of the side wall of the developing case 55Y, and the developing is performed in this gap portion. The chamber 58Y and the stirring chamber 59Y communicate with each other.

  Therefore, the developer moves from the developing chamber 58Y to the agitating chamber 59Y and from the agitating chamber 59Y to the developing chamber 58Y at the communicating portion by the rotation of the first toner conveying screw 53Y and the second toner conveying screw 54Y. As a result, the developer is conveyed in the developing chamber 58Y and the stirring chamber 59Y so as to circulate in a fixed direction that is counterclockwise in FIG. 3B.

  The developing chamber 58Y forms a first section in which the developer is supplied to the developing roller 51Y while being conveyed in the first direction. The agitating chamber 59Y forms a second section where the developer is conveyed from the developing chamber 58Y. The agitating chamber 59Y also functions as a third section where the developer is conveyed in the second direction and supplied to the developing chamber 58Y.

  In the present embodiment, the second compartment and the third compartment are a common space as the stirring chamber 59Y, but these may be separate spaces as long as the developer is circulated. . In this embodiment, the first direction and the second direction are parallel to each other. However, when the second direction draws a curve, or the second section and the third section are configured by separate spaces. They may be non-parallel to each other, such as bent.

  The driving means can change the rotation speeds of the first toner conveyance screw 53Y and the second toner conveyance screw 54Y under the control of the controller, and the rotation speeds of the first toner conveyance screw 53Y and the second toner conveyance screw 54Y can be changed. By changing it, the transport speed of the developer is changed.

  The toner concentration detection sensor 92Y detects the magnetic permeability of the developer in the developing case 55Y and converts the detected value to detect the toner concentration contained in the developer. The toner concentration detection sensor 92Y is disposed below the second toner conveying screw 54Y, but is disposed below the first toner conveying screw 53Y, and the developer is separated from the developing roller 51Y and dropped as described later. In this case, the toner density of the developer immediately after dropping may be detected.

  As will be described later with reference to FIG. 5, the toner supply mechanism 80 includes a toner conveying screw 136 and a replenishment motor M3. When the toner density detection sensor 92Y detects that the toner density contained in the developer in the developing case 55Y is lower than the predetermined density, the toner density is judged to be insufficient and the coil is driven to rotate. To do. Thus, an appropriate amount of yellow toner is supplied and supplied from the toner bottle 9Y to the developer in the developing unit 50Y through the supply port 91Y.

  The toner supplied into the developing unit 50Y main body 99 through the supply port 91Y falls on the second toner conveying screw 54Y in the stirring chamber 59Y as the second partition. That is, the supply port 91Y is disposed at a position where the toner is supplied to the second toner conveying screw 54Y.

  The yellow toner replenished from the supply port 91Y is agitated and mixed with the developer by the second toner conveying screw 54Y and the first toner conveying screw 53Y, and the agitated and mixed developer is supplied to the developing roller 51Y.

  The stirring and mixing of the newly replenished toner and the developer is mainly performed in the stirring chamber 59Y as the second partition, and therefore the stirring chamber 59Y as the second partition functions as a toner density adjustment space. The newly replenished toner is charged by being charged by friction between the toners or the carrier during stirring and mixing.

  The first toner conveying screw 53Y and the second toner conveying screw 54Y function as a developer agitating unit that agitates the developer in the developing case 55Y. This agitation action is obtained by causing the developer to be swung up and down when the developer moves along the screw portions 85Y and 86Y.

  In the developing unit 50Y, the developer in the developing chamber 58Y is carried in a spike shape on the developing sleeve 56Y by the magnetic force of the magnet 57Y. The developing roller 51Y functions as an agent carrier that carries the developer contained in the developing case 55Y. The amount of developer carried by the developing sleeve 56Y is regulated by the developing blade 52Y.

  The layered developer that is regulated and has an appropriate amount on the developing sleeve 56Y is conveyed to the developing region between the developing roller 51Y and the photosensitive drum 20Y by the rotation of the developing sleeve 56Y in the direction of the arrow C1.

  In the developing region, the yellow toner in the developer charged by the stirring of the first toner conveying screw 53Y and the second toner conveying screw 54Y is subjected to the developing bias by the bias applying means, and is applied to the surface of the photosensitive drum 20Y. The electrostatic latent image is electrostatically transferred to the formed electrostatic latent image, and the electrostatic latent image is visualized as a yellow toner image.

  In this manner, the yellow toner is consumed by developing the electrostatic latent image on the surface of the photosensitive drum 20Y, and the developer whose yellow toner density is reduced is retained on the developing sleeve 56Y while being held on the developing sleeve 56Y. The sheet is further conveyed by the rotation in the C1 direction, is separated from the developing sleeve 56Y at a portion where the magnetic force of the magnet 57Y is weak, falls, and is stirred and mixed with another developer.

  In this embodiment, the DC component developing bias is applied by the bias applying means. However, the developing bias may be an AC component, or an AC component superimposed on the DC component.

  As already described, the developer is stirred to charge the toner contained in the developer in order to develop the electrostatic latent image. However, the toner gradually deteriorates due to stirring. On the other hand, when image formation with a low toner consumption rate, for example, image formation with a low image area rate is continuously performed, the toner tends to deteriorate before the toner is consumed, the fluidity is lowered, and the development performance is reduced. descend.

  Accordingly, the developing units 50Y, 50C, 50M, and 50Bk detect or reduce the fluidity of the developer by staying and adjusting the toner concentration in the developer when the stay is detected. It is like that. Means, configurations, and the like for doing this are similarly provided in the developing units 50Y, 50C, 50M, and 50Bk, respectively.

(Drive coupling on the main body side of the image forming apparatus)
An end plate 93a is disposed on the main body side of the image forming apparatus to which the process unit 95Y is mounted as shown in FIGS. 4A and 4B. The end plate 93a is located on the back side in the insertion direction of the process unit 95Y with respect to the main body 99 of the image forming apparatus 100. From this end plate 93a, drive couplings for driving the respective rotating shafts of the photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, and the developing unit 50Y disposed in the process unit 95Y protrude.

  Here, the drive coupling for driving the rotating shaft of the developing unit 50Y excluding the photosensitive drum 20Y from the process unit 95Y will be described. As shown in FIG. 4B, a rotating shaft 96 for driving the toner conveying screw 54Y of the developing unit 50Y is supported on a support plate 93b attached to the outside of the end plate 93a. The rotary shaft 96 is driven by a drive motor disposed on the back side of the end plate 93a on the main body 99 side. As the drive motor, a stepping motor can be used in addition to a normal general-purpose motor.

  A drive coupling 87 is attached to the tip of the rotating shaft 96. The drive coupling 87 rotates integrally with the fan-shaped filler 101 attached to the rotation shaft 84Y. In addition, an optical sensor 102 that detects the presence or absence of the filler 101 by light conduction and interruption is disposed so as to sandwich the rotation trajectory of the filler 101.

  As shown in FIG. 4C (a), the drive coupling 87 has a female shape formed on the inner periphery of the cylindrical member at intervals of 120 °, and has connecting recesses that are tripod-like when viewed from the front (θ = 120 °). In addition, the passive coupling 88 disposed in the main body 99 of the image forming apparatus 100 has connection projections in the form of a tripod in a front view as a male shape at intervals of 120 ° around the rotation axis (θ = 120 °). When the developing unit 50Y is attached to the main body 99 of the image forming apparatus 100, the female type of the drive coupling 87 is detachably engaged with the male type of the passive coupling 88 of the developing unit 50Y. ing.

  In addition, the coupling shape mentioned above is an illustration, Comprising: It is not limited to such a specific shape. Of course, any coupling shape or joint shape capable of transmitting the necessary rotational force can be used.

  The home position of the drive coupling 87, which will be described later, is not limited to the rotation stop position at one specific position in the rotation direction 360 °. That is, when the drive coupling 87 has a circumferentially repeated shape at intervals of 120 ° as described above, three specific positions at intervals of 120 ° can be set as rotation stop positions.

(Toner supply mechanism)
In the main body 99 of the image forming apparatus 100, toner bottles 9Y, 9C, 9M, 9Bk, and 9S positioned at the upstream end of the toner supply mechanism 80 are disposed as shown in FIGS. In FIG. 5, the toner supply mechanism 80 from the spot color toner bottle 9S will be described, but the toner supply mechanisms of other YCMBk toner bottles are the same.

  The special color toner bottle 9S is horizontally disposed at a predetermined mounting position on the upper portion of the main body 99. The toner bottle 9S is detachably attached to the main body 99 in the horizontal arrow direction of FIG. A coupling of the bottle drive motor M1 is detachably connected to the bottom side end of the toner bottle 9S.

  A diaphragm pump P, which is a kind of powder air pump, is disposed at a position away from the toner bottle 9S. The toner bottle 9S and the diaphragm pump P are connected by a toner transport tube 94. One end of the toner transport tube 94 is connected to the outlet of the toner bottle 9S. The other end of the toner transport tube 94 is connected to the suction port P1 of the diaphragm pump P.

  On the diaphragm pump P, a diaphragm pump drive motor M2 is disposed. Diaphragm pump P has an eccentric shaft attached to the rotating shaft of diaphragm pump drive motor M2. By rotating the eccentric shaft, a diaphragm (not shown) in the diaphragm pump P is repeatedly bent and deformed to increase or decrease the inner volume of the diaphragm pump P.

  Thus, the toner is moved from the suction port P1 of the diaphragm pump P toward the discharge port P2. Instead of the diaphragm pump P, other pumps that can suck powder, such as a Mono pump and a suction type uniaxial eccentric screw pump, may be used.

  A sub hopper 120 extending in the horizontal direction is disposed below the diaphragm pump P. An inlet 120 a formed at the top of the sub hopper 120 is connected to the discharge port P <b> 2 of the diaphragm pump P. Further, the developing unit 50S is connected to an outlet 120b disposed in the lower portion of the sub hopper 120. A toner end sensor 137 is disposed on the wall surface of the sub hopper 120.

  A toner conveying screw 136 is horizontally disposed inside the sub hopper 120. The toner conveying screw 136 is driven by a replenishing motor M3. A replenishment clutch CL, gears 130 to 133, and a rotary shaft 140 are disposed between the sub hopper 120 and the replenishment motor M3. The rotation of the replenishing motor M3 is transmitted in the order of gear 130 → gear 131 → rotating shaft 140 → gear 132 → gear 133 → replenishing clutch CL.

  When the toner end sensor 137 detects a decrease in the toner surface, the diaphragm pump drive motor M2 is driven to supply the special color toner to the sub hopper 120. When the replenishing clutch CL is connected, the toner conveying screw 136 of the sub hopper 120 is rotated. When the toner conveying screw 136 rotates, the special color toner is supplied from the outlet 120b to the special color developing unit 50S. When the supply clutch CL is disconnected, the toner conveying screw 136 stops rotating. When the toner conveying screw 136 stops rotating, the supply of the special color toner to the special color developing unit 50S is stopped.

  The spot color developing unit 50S can be attached to and detached from the main body 99 in FIG. 5 in the horizontal arrow direction. This horizontal arrow direction coincides with the axial direction of the rotation shafts (rotation shaft 83Y, rotation shaft 84Y, and rotation shaft of the developing roller 51Y) of the spot color developing unit 50S. A drive coupling 87 is rotatably disposed on the main body 99 side, and the drive coupling 87 is rotationally driven by a developing motor M4 via gears 134 and 135.

  The spot color developing unit 50S is replaced more frequently than the other developing units. For this reason, the possibility that the coupling is damaged or broken by replacing the spot color developing unit 50S is higher than that of the other developing units. By using the embodiment of the present invention, the possibility of damage and breakage of the drive coupling 87 and the passive coupling 88 due to the replacement of the spot color developing unit 50S can be reduced.

(controller)
FIG. 7 is a block diagram of the controller 110 of the image forming apparatus 100. The controller 110 is composed of a CPU, RAM, and ROM. Image forming units 60Y, 60M, 60C, 60Bk, 60S, motors M1 to M6, supply clutch CL, optical scanning device 8, transfer belt unit 10, temperature / humidity sensor, optical sensor 102, and the like are electrically connected to controller 110. ing. The controller 110 controls these various devices based on a control program stored in the RAM or ROM.

  “CPU” is an abbreviation for Central Processing Unit and constitutes a calculation means. “RAM” is an abbreviation for Random Access Memory and constitutes data storage means. “ROM” is an abbreviation for Read Only Memory, and constitutes data storage means.

  Of the motors M1 to M6, the motors M1 to M4 are the motors M1 to M4 shown in FIG. The image forming unit 60S and the driving roller 72 of the intermediate transfer belt 11 are driven by the motor M4. The four image forming units 60Y, 60C, 60M, and 60Bk are driven by the motor M5. The paper feed roller 3 and the fixing roller 62 are driven by the motor M6. By reducing the number of motors in this way, the image forming apparatus 100 can be reduced in size and cost.

  The controller 110 also controls image forming conditions for forming an image. Specifically, the controller 110 performs control to individually apply a charging bias to each charging member in each image forming unit 60. Thereby, each charging member is uniformly charged to the drum charging potential for each color photosensitive drum 20.

  The controller 110 individually controls the powers of the five semiconductor lasers of the optical scanning device 8 corresponding to the image forming units 60.

  In addition, the controller 110 performs control to apply a developing bias of developing bias values for Y, C, M, Bk, and S to the developing roller of each image forming unit 60. As a result, a developing potential for electrostatically moving the toner from the sleeve surface side to the photosensitive drum 20 side is applied between the electrostatic latent image on the photosensitive drum 20 and the developing roller 51, thereby generating the electrostatic latent image. develop.

  Further, the controller 110 executes process control as image density control for optimizing the image density of each color when the power is turned on or every time a predetermined number of prints are performed.

(Replace special color toner)
FIG. 8 is a flowchart showing an example of replacement of spot color toner. In this replacement example, the clear toner being used is changed to white toner. First, it is assumed that printing is performed using clear toner in addition to the four colors YMCBk.

  To enable the use of white toner from this state, it is necessary to replace the toner bottle of clear toner with a toner bottle of white toner, and replace the development unit of clear toner with a development unit of white toner. is necessary. Furthermore, it is necessary to discharge the clear toner (residual clear toner) remaining in the toner transport tube 94, the diaphragm pump P, and the sub hopper 120.

  Therefore, by driving the diaphragm pump P with the clear toner bottle 9S removed, the remaining clear toner is taken into the clear toner developing unit 50S.

  When all of the remaining clear toner remains in the clear toner developing unit 50S, the developing unit 50S is removed and a white developing unit (not shown) is attached instead. A white toner bottle is attached instead of the clear toner bottle 9S.

  When the white developing unit is mounted, the drive coupling 87 on the main body 99 side and the passive coupling 88 of the white developing unit are engaged in the axial direction. As will be described later, the drive coupling 87 on the main body side can be stopped at a fixed home position by controlling the rotation stop position of the developing motor M4 as the drive means of the main body 99. Thereby, the passive coupling 88 of the white developing unit can be smoothly engaged with the drive coupling 87.

  The rotational position of the passive coupling 88 of the new white developing unit is adjusted at the time of shipment from the factory so that the home position of the drive coupling 87 on the main body side matches the rotational position.

(Toner discharge mode)
To reattach the original clear developing unit 50S after using the white developing unit, the toner discharge mode is executed after removing the white toner bottle. Thereafter, the clear toner bottle 9S is remounted, and the white developing unit is replaced with the clear developing unit 50S.

  The toner discharge mode is for discharging the toner in the toner supply mechanism 80 to the outside, and can be performed, for example, by operating the operation panel 160 shown in FIG. The operation panel 160 is disposed at a position where it is easy to operate, such as the upper surface of the image forming apparatus main body 99.

  The operation panel 160 includes a keyboard 161 having a plurality of keys (or buttons) for operation / instruction input, and a display panel 162 such as a liquid crystal display panel for displaying the state of the image forming apparatus and setting information. A toner discharge mode button 163 is provided adjacent to the keyboard 161. When the user depresses the toner discharge mode button 163, the toner discharge mode is started.

  The flow of FIG. 8 will be further described with reference to FIGS. As shown in FIG. 9, in the toner discharge mode, the diaphragm pump P is operated at a high rotational speed, and residual special color toner such as the toner transport tube 94 is introduced into the sub hopper 120 through the diaphragm pump P. Further, the toner conveying screw 136 of the sub hopper 120 and the first toner conveying screw 53 and the second toner conveying screw 54 of the developing unit 50 are driven, and the residual toner in the sub hopper 120 is taken into the developing unit 50.

  In the toner discharge mode, as shown in FIG. 10, the waste toner motor, the waste toner bottle motor, the developing motor M4, the toner supply motor M3, and the supply clutch CL are turned on. Although not shown, the waste toner motor and the waste toner bottle motor are disposed on the main body side. When these are driven for a predetermined time, discharge of residual toner in the toner supply mechanism 80 is completed. Thereafter, the waste toner motor, the waste toner bottle motor, the toner supply motor M3, and the supply clutch CL are turned off.

  The developing motor M4 stops at a predetermined rotational position (home position) through the developing motor home position stop control. Thereby, the drive coupling 87 on the main body side stops at the rotation position of the home position.

  The rotational speed before stopping the rotation of the drive coupling 87 or the deceleration acceleration at the time of stopping the rotation is preferably small so that the drive coupling 87 is stopped without displacement. If the rotation speed or deceleration acceleration is too small, it takes too much time for the drive coupling 87 to stop. Therefore, the drive coupling 87 is preferably stopped at the home position at a moderately large rotational speed or deceleration acceleration.

  The rotational speed or deceleration acceleration is set to be smaller than at least the rotational speed or deceleration acceleration when the drive coupling 87 stops in the toner discharge mode, except in the toner discharge mode. In order to reduce the rotation speed or deceleration acceleration, the rotation speed of the developing motor M4 is decreased before or after the toner discharge mode is completed. The deceleration control is performed by the controller 110.

  As a result, in the developing motor home position stop control, the drive coupling 87 rotates at a relatively low rotational speed. Accordingly, the deceleration acceleration when the rotation of the drive coupling 87 is stopped is reduced, and the variation in the rotation stop position (home position) is reduced. And even if the developing unit as the driven body is replaced, the possibility of the collision of the engaging portions between the couplings can be greatly reduced.

(Development motor home position stop control)
The flowchart of FIG. 11 is a flow for executing the rotation stop position control (home position stop control) of the developing motor M4 (drive coupling 87) in the toner discharge mode.

  In the toner discharge mode, if the 5st developing motor M4 is being driven, the home position stop control of the 5st developing motor M4 is started in step S1.

  In the toner discharge mode, there is a high possibility that the developing unit 50 is replaced with another developing unit 50. On the other hand, in a mode other than the toner discharge mode, even if the developing unit 50 is removed once, there is a high possibility that the same developing unit 50 is mounted again.

  Therefore, the drive coupling 87 is stopped at the home position only when the developing unit 50 is detached and attached in the toner discharge mode. It takes more time to stop at the home position than it would otherwise. For this reason, the waiting time in the non-toner discharge mode can be shortened as follows according to the embodiment of the present invention.

  In a mode other than the toner discharge mode (non-toner discharge mode), the developing unit 50 once removed is often mounted again. The developing unit 50 once removed remains in the same phase as the rotational position of the drive shaft on the main body side, so that the couplings may interfere with each other in the axial direction even if re-attached without home position stop control. Absent.

  Therefore, in the non-toner discharging mode, the developing motor is quickly stopped at an arbitrary rotation stop position, and the developing unit is remounted. As a result, the developing unit can be smoothly remounted in a short working time, and the coupling can be engaged without damaging or breaking the coupling.

  As described above, after the home position stop control of the 5st developing motor M4 is started in step S1, it is determined in step S2 whether the driving time of the developing motor M4 has passed, for example, 2 seconds. The measurement start time of “2 seconds” is a time when a predetermined position in the circumferential direction of the drive coupling 87 passes a predetermined position on the main body 99 side at a predetermined low speed.

  This “time point” can be detected by the filler 101 and the optical sensor 102. The drive coupling 87 reaches a predetermined home position by the rotation for “2 seconds”. If it is determined that two seconds have elapsed, it is determined in step S3 whether or not the optical sensor 102 that detects the home position of the 5st drive coupling 87 has detected “existence” from “absence” of the filler 101.

  The home position arrival detection can also be performed by measuring the rotation speed of the developing motor M4 instead of measuring the time of “2 seconds”. Further, when the drive coupling 87 is driven by a stepping motor, the optical sensor 102 is stopped when a predetermined step (for example, 10 steps) is actuated after detecting “absent” to “present” of the filler 101. . As a result, the drive coupling 87 can be stopped at the home position with higher accuracy.

  If the filler is “present” (home position), the home position detection is successful in step S6. In step S7, the 5St developing motor M4 is stopped.

  If it is determined in step 3 that there is no filler, in step S4, for example, 3 seconds are awaited. If 3 seconds have elapsed, it is determined that the home position detection is abnormal in step S5. Thereafter, in step S7, the 5st developing motor M4 is stopped.

  By discharging the toner to the developing unit and reusing it in the toner discharge mode of the toner supply mechanism 80, the toner discharged at the time of toner replacement can be used when the user wants to use the toner.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the driven body is a spot color developing unit, but the driven body may be other than the spot color developing unit. For example, the present invention can be applied to each YCMBk developing unit that is detachably attached to the main body, or the present invention can be applied to a toner supply container that is detachably attached to the main body.

  In the embodiment, the developing unit as a driven member is detached from the main body of the image forming apparatus in the axial direction of the developing unit. However, the driven member or the developing unit is perpendicular to the axial direction. You may make it remove | desorb by direction. Also in this case, the drive coupling on the main body side is controlled to stop at a predetermined rotation stop position by the controller, so that the coupling on the driving side and the passive side can be smoothly attached and detached even when the driven body is replaced.

9: Toner bottle 83Y, 84Y: Rotating shaft 85Y, 86Y: Screw part 87: Passive coupling 88: Drive coupling 91Y: Supply port 92Y: Toner density detection sensor 93a: End plate 93b: Support plate 94: Toner transport tube 95Y : Process unit 99: Image forming apparatus main body 100: Image forming apparatus 110: Controller 120: Sub hoppers 130 to 135: Gear 136: Toner transport screw 137: Toner end sensor 140: Rotating shaft 160: Operation panel 163: Toner discharge mode button CL: Supply clutch M1: Bottle drive motor M2: Diaphragm pump drive motor M3: Supply motor M4: Development motor P: Diaphragm pump

JP 2007-171498 A JP 2007-316313 A JP 2007-304173 A (FIGS. 11 and 12) JP-A-4-240870 JP 2005-292676 A (0008 steps)

Claims (7)

An electrophotographic image forming apparatus, wherein the image forming apparatus includes:
A drive coupling disposed in the main body of the image forming apparatus;
Drive means for rotating the drive coupling;
A controller for controlling the driving means;
A developing means having at least one driven member, and detachable from the main body of the image forming apparatus;
A passive coupling coupled to the driven body;
Toner replenishing means for replenishing toner as developer to the developing means,
In the image forming apparatus, when the developing unit is attached to the main body of the image forming apparatus, the passive coupling engages with the drive coupling, and the driven member is driven by the driving unit.
The image forming apparatus has a toner discharge mode for discharging the toner in the toner replenishing means, and in the toner discharge mode, the drive is performed so that the drive coupling stops at a predetermined rotation stop position. Means are controlled by the controller; and
In the non-toner discharge mode other than the toner discharge mode, when the drive coupling is rotating, the drive means is controlled by the controller so that the drive coupling quickly stops at an arbitrary rotation stop position. An image forming apparatus.   The controller controls the speed at which the drive coupling stops at a predetermined rotation stop position in the toner discharge mode to be lower than the speed at which the drive shaft stops in a mode other than the toner discharge mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed.   The image forming apparatus according to claim 1, wherein a direction in which the developing unit is attached to and detached from a main body of the image forming apparatus is an axial direction of a rotation shaft of the driven body.   2. The image forming apparatus according to claim 1, wherein a direction in which the developing unit is attached to and detached from a main body of the image forming apparatus is a direction perpendicular to an axial direction of a rotation shaft of the driven body.   2. The image forming apparatus according to claim 1, wherein the passive coupling is connected to a toner conveying screw as the driven body of the developing unit.   6. The image forming apparatus according to claim 5, wherein the developing unit is a special color developing unit having a special color toner such as white or clear color.   It has five or more image forming units that have an image carrier and development unit, and can print with more than five colors by adding clear toner or white toner as special color toner in addition to each toner of yellow, cyan, magenta and black. The image forming apparatus according to claim 6, wherein the image forming apparatus is provided.