JP2023014473A - image forming device - Google Patents

Abstract

To provide an image forming device with which it is possible to smoothly convey a waste developer in a collection path for collecting a waste developer and suppress toner clogging in the collection path.SOLUTION: An image forming device comprises a photoreceptor drum, a developing unit, a cleaning unit, a collection unit 11, and a control unit. The collection unit 11 includes a collection path 111a where a developer disposal path 112a in which a waste developer from the ejection unit of the developing unit is conveyed and toner disposal paths 113a, 114a in which a waste toner from the cleaning unit is conveyed join together, and collects a waste developer that includes a waster toner and a waste carrier. The collection path 111a has at least in part a point where flow resistance is large. When the weight ratio of the waste carrier to the waster toner of the waste developer in the collection path 111a is less than a prescribed value, the control unit executes a developer ejection process of ejecting a developer from a developer container while not forming an image.SELECTED DRAWING: Figure 5

Description

The present invention relates to an image forming apparatus.

In electrophotographic image forming apparatuses such as copiers and printers, an electrostatic latent image formed on the surface of an image bearing member such as a photoreceptor drum is developed by attaching toner to it so that it can be printed on a recording medium such as paper. Apparatus for forming a transferred toner image are widely available. In the developing section, in order to continuously form a uniform image, the developer containing the toner accommodated in the developing container is conveyed while being agitated within the developing container.

For example, in the conventional image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-200000, developer containing toner and carrier is replenished, the developer is supplied to the developing roller, and the amount of developer to be discharged to the outside is controlled according to the rotation speed. A development station having a variable agitating member is provided. This image forming apparatus switches the speed from the second speed to the first speed based on the amount of developer increased when the stirring member is rotated at a second speed lower than the first speed, and rotates the stirring member for a predetermined time. rotate. As a result, even if the rotation speed of the stirring member is switched, the amount of developer in the developing section can be stabilized.

JP 2013-037257 A

In the case of the prior art, the developer is not discharged from the development station when the low speed drive continues in the development station. For example, when the waste developer discharged from the developing section and the waste toner remaining on the surface of the image bearing member and removed are combined and transported to collect the waste toner, the developer is discharged from the developing section. If it is not discharged, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path may become low. As a result, the fluidity of the waste developer in the recovery path is significantly reduced, and for example, if there is a location on the recovery path with greater flow resistance than the toner disposal path, there is a problem that toner clogging occurs at that location. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an image forming apparatus capable of smoothly conveying a waste developer in a collection path for collecting the waste developer and suppressing toner clogging on the collection path. It is an object of the present invention to provide a forming apparatus.

In order to solve the above problems, the image forming apparatus of the present invention includes an image carrier, a developing section, a cleaning section, a recovery section, and a control section. The image carrier carries a toner image on its surface. The developing section includes a developing container containing a two-component developer containing toner and carrier, a developer carrying member carrying the developer in the developing container, and discharging excess developer from the developing container. and a discharging portion for developing the electrostatic latent image formed on the surface of the image carrier with the toner to form the toner image. The cleaning section removes the toner remaining on the surface of the image carrier. The recovery unit is a recovery path that joins a developer disposal path through which the waste developer discharged from the discharge unit is transported and a toner disposal path through which the waste toner removed by the cleaning unit is transported. and recovers the waste developer including the waste toner and the waste carrier through the recovery path. The control section controls operations of the image carrier, the developing section, the cleaning section, and the collection section. At least a portion of the recovery path has a portion with greater flow resistance than the toner disposal path. When the weight ratio of the waste carrier to the waste toner in the waste developer in the recovery path is less than a predetermined value, the control unit removes the toner from the developer container through the discharge unit during non-image formation. A developer discharge process for discharging the developer is executed.

According to the configuration of the present invention, by discharging the developer from the developing container through the discharging portion, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path can be increased. Fluidity can be favorably maintained. As a result, the waste developer can be smoothly transported in the recovery path, and toner clogging in the recovery path can be suppressed.

1 is a schematic vertical sectional front view of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a block diagram showing the configuration of the image forming apparatus of FIG. 1; FIG. 2 is a schematic vertical cross-sectional front view of the periphery of an image forming unit of the image forming apparatus of FIG. 1; FIG. 4 is a horizontal cross-sectional plan view of a developing section of the image forming section of FIG. 3; FIG. 2 is a schematic vertical cross-sectional rear view of the collection unit of the image forming apparatus of FIG. 1; FIG.

Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following contents.

FIG. 1 is a schematic vertical sectional front view of an image forming apparatus 1 according to an embodiment. FIG. 2 is a block diagram showing the configuration of the image forming apparatus 1 of FIG. 1. As shown in FIG. FIG. 3 is a schematic vertical sectional front view around the image forming unit 20 of the image forming apparatus 1 of FIG. An example of the image forming apparatus 1 of this embodiment is a tandem color printer that transfers a toner image onto a sheet S using an intermediate transfer belt 31 . The image forming apparatus 1 may be, for example, a so-called multifunction machine having functions such as printing, scanning (image reading), and facsimile transmission.

As shown in FIGS. 1, 2 and 3, the image forming apparatus 1 includes a paper feeding section 3, a paper conveying section 4, an exposure section 5, an image forming section 20, a transfer section 30, A fixing unit 6 , a paper discharge unit 7 and a control unit 8 are provided.

The paper feeding unit 3 accommodates a plurality of sheets S, and separates and feeds out the sheets S one by one during printing. The paper conveying unit 4 conveys the paper S fed from the paper feeding unit 3 to the secondary transfer unit 33 and the fixing unit 6, and further discharges the fixed paper S from the paper discharge port 4a to the paper discharge unit 7. . When double-sided printing is performed, the paper conveying unit 4 distributes the paper S after fixing on the first surface to the reversing conveying unit 4c by the branching unit 4b, and transfers the paper S again to the secondary transfer unit 33 and the fixing unit 6. transport. The exposure unit 5 irradiates the image forming unit 20 with laser light controlled based on image data.

The image forming section 20 is arranged below the intermediate transfer belt 31 . The image forming section 20 includes a yellow image forming section 20Y, a cyan image forming section 20C, a magenta image forming section 20M, and a black image forming section 20B. These four image forming units 20 have the same basic configuration. Accordingly, in the following description, the identification symbols "Y", "C", "M", and "B" representing each color may be omitted unless otherwise specified.

The image forming section 20 includes a photosensitive drum (image bearing member) 21 rotatably supported in a predetermined direction (clockwise in FIGS. 1 and 3). The image forming section 20 further includes a charging section 22, a developing section 40, and a drum cleaning section 23 arranged around the photosensitive drum 21 along the direction of rotation thereof. A primary transfer section 32 is arranged between the developing section 40 and the drum cleaning section 23 .

The photosensitive drum 21 has a photosensitive layer on its outer peripheral surface. The charging section 22 charges the surface of the photosensitive drum 21 to a predetermined potential. The exposure unit 5 exposes the surface of the photosensitive drum 21 charged by the charging unit 22 to form an electrostatic latent image of the document image. The developing unit 40 supplies toner to the electrostatic latent image and develops it to form a toner image. As a result, the photosensitive drum 21 carries a toner image on its surface. Each of the four image forming units 20 forms toner images of different colors. The drum cleaning unit 23 cleans the surface of the photosensitive drum 21 by removing toner and the like remaining on the surface of the photosensitive drum 21 after the toner image is primarily transferred onto the surface of the intermediate transfer belt 31 . In this way, the image forming section 20 forms an image on the sheet S. As shown in FIG.

The transfer section 30 includes an intermediate transfer belt (image carrier) 31, primary transfer sections 32Y, 32C, 32M, and 32B, a secondary transfer section 33, and a belt cleaning section 34, as shown in FIG. . The intermediate transfer belt 31 is arranged above the four image forming units 20 . The intermediate transfer belt 31 is rotatably supported in a predetermined direction (counterclockwise in FIG. 1). The intermediate transfer belt 31 is an intermediate transfer member onto which the toner images carried on the surfaces of the photosensitive drums 21 of the four image forming units 20 are sequentially superimposed and primarily transferred. The four image forming units 20 are arranged in a line from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 31 in a so-called tandem system.

The primary transfer sections 32Y, 32C, 32M, and 32B are arranged above the image forming sections 20Y, 20C, 20M, and 20B of each color with the intermediate transfer belt 31 interposed therebetween. The secondary transfer section 33 is located upstream of the fixing section 6 in the sheet conveying direction of the sheet conveying section 4, and the intermediate transfer belt 31 is located further than the image forming sections 20Y, 20C, 20M, and 20B of the transfer section 30 for each color. is arranged on the downstream side in the rotational direction of the The belt cleaning unit 34 is arranged upstream in the rotation direction of the intermediate transfer belt 31 from the image forming units 20Y, 20C, 20M, and 20B of each color.

The toner images are primarily transferred onto the surface of the intermediate transfer belt 31 by the primary transfer portions 32Y, 32C, 32M, and 32B of each color. As the intermediate transfer belt 31 rotates, the toner images of the four image forming units 20 are successively superimposed and transferred onto the intermediate transfer belt 31 at a predetermined timing. , magenta, and black are superimposed to form a color toner image.

The color toner image on the surface of the intermediate transfer belt 31 is transferred onto the sheet S synchronously fed by the sheet conveying section 4 at the secondary transfer nip formed in the secondary transfer section 33 . The belt cleaning unit 34 cleans the surface of the intermediate transfer belt 31 by removing toner and the like remaining on the surface after the secondary transfer.

The fixing section 6 is arranged above the secondary transfer section 33 . The fixing section 6 heats and presses the sheet S onto which the toner image has been transferred, thereby fixing the toner image onto the sheet S. As shown in FIG.

The paper discharge section 7 is arranged above the transfer section 30 . The paper S on which the toner image has been fixed and printing has been completed is conveyed to the paper discharge section 7 .

The control unit 8 includes a CPU, an image processing unit, a storage unit, and other electronic circuits and electronic parts (all not shown). The CPU performs processing related to the functions of the image forming apparatus 1 by controlling the operation of each component provided in the image forming apparatus 1 based on control programs and data stored in the storage unit. The paper feeding unit 3, the paper conveying unit 4, the exposure unit 5, the image forming unit 20, the transfer unit 30, and the fixing unit 6 individually receive commands from the control unit 8, and print on the paper S in conjunction with each other. . The storage unit is composed of a combination of a non-volatile storage device such as a program ROM (Read Only Memory) or a data ROM and a volatile storage device such as a RAM (Random Access Memory).

Next, the configuration around the image forming section 20 will be described using FIGS. 4 and 5 in addition to FIGS. 2 and 3. FIG. 4 is a horizontal cross-sectional plan view of the developing section 40 of the image forming section 20 of FIG. FIG. 5 is a schematic vertical sectional rear view of the collection unit 11 of the image forming apparatus 1 of FIG.

The developing section 40 supplies toner to the surface of the photoreceptor drum 21 . The developing section 40 includes a developer container 41 , a first conveying member 42 , a second conveying member 43 , a developing roller (developer carrier) 44 , a regulation blade 45 and a discharge section 46 .

The developer container 41 has an elongated shape extending along the axial direction of the photoreceptor drum 21 (the depth direction of the paper surface of FIG. 3), and is arranged with its longitudinal direction horizontal. The developer container 41 accommodates, as the developer to be supplied to the photosensitive drum 21, a two-component developer containing, for example, toner and magnetic carrier.

The developer container 41 has a partition portion 411 , a first transfer chamber 412 , a second transfer chamber 413 , a first communication portion 414 , and a second communication portion 415 .

The partition part 411 is provided in the lower part inside the developer container 41 . The partition portion 411 is arranged substantially in the center of the direction crossing the longitudinal direction of the developer container 41 (horizontal direction in FIG. 3, vertical direction in FIG. 4). The partition portion 411 is formed in a substantially plate shape extending in the longitudinal direction and the vertical direction of the developer container 41 . The partition portion 411 partitions the inside of the developer container 41 in a direction crossing the longitudinal direction.

The first transport chamber 412 and the second transport chamber 413 are provided inside the developer container 41 . The first transfer chamber 412 and the second transfer chamber 413 are formed by dividing the inside of the developer container 41 by the partition portion 411, and are arranged side by side at substantially the same height.

The second transport chamber 413 is arranged below and adjacent to the arrangement area of the developing roller 44 in the developer container 41 . That is, the second transport chamber 413 faces the developing roller 44 . The first transport chamber 412 is arranged in a region in the developer container 41 that is farther away from the developing roller 44 than the second transport chamber 413 is. A developer supply port 412a is opened in the first transport chamber 412, and the developer is supplied through the developer supply port 412a.

The first communicating portion 414 and the second communicating portion 415 are arranged on the outer sides of both ends of the partition portion 411 in the longitudinal direction. The first communicating portion 414 and the second communicating portion 415 extend in a direction intersecting the longitudinal direction of the partition portion 411 (horizontal direction in FIG. 3, vertical direction in FIG. 4), that is, the thickness direction of the substantially plate-shaped partition portion 411. , the first transfer chamber 412 and the second transfer chamber 413 are communicated. In other words, the first transfer chamber 412 and the second transfer chamber 413 communicate with each other at both ends in the longitudinal direction.

The first transport member 42 is arranged in the first transport chamber 412 . The second transport member 43 is arranged inside the second transport chamber 413 . The second conveying member 43 extends parallel to and close to the developing roller 44 . The first conveying member 42 and the second conveying member 43 are supported by the developer container 41 so as to be rotatable about an axis extending horizontally parallel to the developing roller 44 . The basic configurations of the first conveying member 42 and the second conveying member 43 are the same. The first conveying member 42 has a spiral first conveying blade 42 b on the outer peripheral portion of a rotating shaft 42 a extending along the longitudinal direction of the developer container 41 . The second conveying member 43 has a spiral second conveying blade 43b on the outer peripheral portion of a rotating shaft 43a extending along the longitudinal direction of the developer container 41 .

The first conveying member 42 stirs and conveys the developer in the first direction f1 from the first communicating portion 414 side to the second communicating portion 415 side along the axial direction of rotation in the first conveying chamber 412 . . The second conveying member 43 stirs and conveys the developer in the second direction f2 from the second communicating portion 415 side to the first communicating portion 414 side along the axial direction of rotation in the second conveying chamber 413 . . The second direction f2 is opposite to the first direction f1.

The first communication portion 414 allows communication between the downstream end of the second transfer chamber 413 in the second direction f2 and the upstream end of the first transfer chamber 412 in the first direction f1. The developer is conveyed from the second conveying chamber 413 side toward the first conveying chamber 412 side through the first communicating portion 414 . The second communication portion 415 allows communication between the downstream end of the first transfer chamber 412 in the first direction f1 and the upstream end of the second transfer chamber 413 in the second direction f2. The second communication portion 415 transports the developer from the first transport chamber 412 side toward the second transport chamber 413 side.

The developing roller 44 is arranged above the second transport chamber 413 inside the developer container 41 . A part of the surface of the developing roller 44 is exposed from the developer container 41 and is arranged to face the photosensitive drum 21 . The developing roller 44 is supported by the developing container 41 so as to be rotatable about an axis extending parallel to the axis of the photosensitive drum 21 . The developing roller 44 carries the developer in the second transport chamber 413 . The developing roller 44 supplies the toner in the developing container 41 to the surface of the photoreceptor drum 21 in the area facing the photoreceptor drum 21, and develops the electrostatic latent image to form a toner image.

The regulating blade 45 is arranged on the upstream side in the rotation direction of the developing roller 44 in the area where the developing roller 44 and the photosensitive drum 21 face each other. The regulating blade 45 closely faces the developing roller 44 and is arranged with a predetermined gap between its tip and the surface of the developing roller 44 . The regulation blade 45 extends over the entire area of the developing roller 44 in the axial direction. The regulating blade 45 regulates the layer thickness of developer (toner) carried on the surface of the developing roller 44 and passing through the gap between the tip of the regulating blade 45 and the surface of the developing roller 44 .

The developer in the developer container 41 passes through the first communicating portion 414 and the second communicating portion 415 due to the rotation of the first conveying member 42 and the second conveying member 43 , and passes through the first conveying chamber 412 and the second conveying chamber 413 . in a predetermined circulation direction. At this time, the toner in the developing container 41 is agitated and charged, and carried on the surface of the developing roller 44 . After the layer thickness of the toner carried on the surface of the developing roller 44 is regulated by the regulating blade 45 , the developing roller 44 rotates to transport the toner to the area where the developing roller 44 and the photosensitive drum 21 face each other. When a predetermined development voltage is applied to the developing roller 44 , the toner carried on the surface of the developing roller 44 is exposed in the area facing the photosensitive drum 21 due to the potential difference between it and the potential of the surface of the photosensitive drum 21 . It moves to the surface of body drum 21 . In this manner, the electrostatic latent image on the surface of photoreceptor drum 21 is developed with toner.

The discharge part 46 is provided further downstream than the downstream end of the second transfer chamber 413 in the second direction f2. The discharge section 46 is connected to the second transfer chamber 413 . The insides of the discharge section 46 and the second transfer chamber 413 communicate with each other. The discharge portion 46 has a developer discharge port 46 a and discharge blades 461 .

The rotating shaft 43 a of the second conveying member 43 extends continuously into the discharge section 46 . One end of the rotating shaft 43a in the axial direction is rotatably supported by the developer container 41 at the downstream end of the discharging portion 46 in the second direction f2 of the second transfer chamber 413 .

The developer discharge port 46 a is arranged at the downstream end of the discharge section 46 with respect to the second direction f<b>2 of the second transport chamber 413 . The developer discharge port 46a opens below the rotating shaft 43a of the second conveying member 43, for example. Excess developer in the developer container 41 is discharged from the developer discharge port 46a. That is, in the discharge section 46, the surplus developer in the second transport chamber 413 is transported toward the developer discharge port 46a.

The discharge blade 461 extends spirally along the axial direction on the outer peripheral portion of the rotating shaft 43 a of the second conveying member 43 . The discharge blade 461 is provided integrally with the rotation shaft 43a, like the second transfer blade 43b. The discharge blade 461 has the same winding direction as the second transfer blade 43b. That is, the developer transport direction in the discharge portion 46 is the same as the second direction f<b>2 of the second transport chamber 413 . As a result, the discharge blade 461 conveys the surplus developer in the discharge portion 46 toward the developer discharge port 46a. Note that the discharge blade 461 has a smaller pitch and a smaller outer diameter than, for example, the second transfer blade 43b.

The second conveying member 43 also includes a restricting portion 43c in addition to the second conveying blade 43b. The restricting portion 43c is provided integrally with the rotary shaft 43a, similarly to the second conveying blade 43b.

The restricting portion 43 c is arranged downstream of the second conveying blade 43 b of the second conveying member 43 with respect to the second direction f<b>2 of the second conveying chamber 413 . The restricting portion 43c faces the connecting portion between the second transfer chamber 413 and the discharging portion 46 in the axial direction of the rotating shaft 43a.

The restricting portion 43c is configured in a blade shape extending spirally along the axial direction on the outer peripheral portion of the rotating shaft 43a. That is, the restricting portion 43 c is formed on the second transport member 43 inside the second transport chamber 413 . The restricting portion 43c has a winding direction opposite to that of the second conveying blade 43b. As a result, the regulation portion 43c blocks the developer that has been conveyed to the vicinity of the downstream end in the second conveyance chamber 413, and regulates the movement of the developer toward the discharge portion 46 side. The regulating portion 43c has a smaller pitch than the second conveying blade 43b.

The outer peripheral portion of the restricting portion 43 c has a predetermined gap (clearance) with the inner surface of the developer container 41 . A predetermined amount or more of the developer in the second transport chamber 413 is transported as surplus developer toward the discharge portion 46 through the gap between the outer peripheral portion of the regulation portion 43c and the inner surface of the developer container 41 .

The drum cleaning unit 23 removes toner remaining on the surface of the photosensitive drum 21 after the primary transfer. The drum cleaning section 23 has a cleaning roller 231 , a cleaning blade 232 and an ejection member 233 .

The cleaning roller 231 contacts the surface of the photoreceptor drum 21 with a predetermined pressure, and is rotated in a direction in which the contact area with the photoreceptor drum 21 moves in the same direction as the photoreceptor drum 21 by a drive section (not shown). The cleaning blade 232 contacts the surface of the photoreceptor drum 21 with a predetermined pressure. The cleaning roller 231 and the cleaning blade 232 clean the surface of the photosensitive drum 21 by removing toner and the like remaining on the surface of the photosensitive drum 21 after the primary transfer. The discharging member 233 has spiral blades, and discharges the waste toner removed from the surface of the photosensitive drum 21 toward the later-described collecting section 11 provided outside the drum cleaning section 23 .

The belt cleaning section 34 also has a structure similar to that of the drum cleaning section 23 . The belt cleaning unit 34 removes toner remaining on the surface of the intermediate transfer belt 31 after the secondary transfer, and discharges the toner toward a recovery unit 11 (described later) provided outside the belt cleaning unit 34 .

The image forming apparatus 1 further includes a recovery unit 11 as shown in FIGS. 1, 2 and 5 . The collecting section 11 is arranged, for example, on the front side or the back side of the image forming section 20 and the transfer section 30 . The collection unit 11 has a housing 111 , a developer disposal pipe 112 , a first toner disposal pipe 113 , a second toner disposal pipe 114 and a collection member 115 .

The housing 111 has an elongated shape extending in the direction in which the four image forming units 20 are arranged (horizontal direction in FIG. 1) and in the vertical direction. A developer disposal pipe 112, a first toner disposal pipe 113, and a second toner disposal pipe 114 are connected to the upper portion of the housing 111 and communicate with each other. The housing 111 accommodates the waste developer discharged from the discharge section 46 of the developing section 40 and the waste toner removed by the drum cleaning section 23 and the belt cleaning section 34 .

The collecting section 11 has four developer disposal pipes 112 individually extending from the discharge sections 46 of the four developing sections 40 . The collection unit 11 also has four first toner disposal pipes 113 individually extending from the four drum cleaning units 23 . A second toner disposal tube 114 extends from the belt cleaning section 34 . That is, the collection unit 11 includes a developer disposal path 112 a through which waste developer is transported from the developing unit 40 , a first toner disposal path 113 a through which waste toner is transported from the drum cleaning unit 23 , and a waste toner from the belt cleaning unit 34 . and a second toner disposal path 114a through which toner is conveyed.

A recovery path 111 a is provided at the bottom inside the housing 111 . The developer disposal path 112a, the first toner disposal path 113a, and the second toner disposal path 114a join together in the collection path 111a. The recovery path 111a extends along the direction in which the four image forming units 20 are arranged side by side. A downwardly opening waste developer discharge port 111b is provided at one end of the bottom of the housing 111 in the direction in which the recovery path 111a extends.

The recovery member 115 is arranged at the bottom inside the housing 111 and on the recovery path 111a. The recovery member 115 is supported by the housing 111 so as to be rotatable about an axis extending along the direction in which the four image forming units 20 are arranged side by side. The recovery member 115 has a helical recovery blade 115b on the outer peripheral portion of a rotating shaft 115a extending along the longitudinal direction of the housing 111 . The recovery member 115 conveys the waste developer and waste toner that have fallen onto the recovery path 111a on the inner bottom of the housing 111 toward the waste developer outlet 111b.

A connection pipe 111c is attached below the waste developer outlet 111b. A waste tank (not shown) is connected to the lower end of the connecting pipe 111c. The recovery path 111a includes a waste developer outlet 111b and a connection pipe 111c. The waste developer discharge port 111b and the connection pipe 111c have a flow resistance greater than that of the first toner disposal path 113a and the second toner disposal path 114a due to, for example, the passage diameter being small and being curved. In other words, the recovery path 111a has, at least in part, a location with greater flow resistance than the toner disposal path.

With the above configuration, the recovery unit 11 recovers the waste developer including the waste toner and the waste carrier through the recovery path 111a. Further, the image forming apparatus 1 includes a photosensitive drum 21 and an intermediate transfer belt 31 as image carriers, a drum cleaning unit 23 and a belt cleaning unit 34 as cleaning units, and a collection unit 11 including a developer disposal path 112a and a second cleaning unit. By including the first toner disposal path 113a, the second toner disposal path 114a, and the collection path 111a, the waste developer including the waste toner and the waste carrier can be easily collected together.

The operations of the photosensitive drum 21 , the developing section 40 , the drum cleaning section 23 , the belt cleaning section 34 , and the collection section 11 are controlled by the control section 8 .

Next, the relationship between the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a and the occurrence of toner clogging at the waste developer outlet 111b or the connection pipe 111c on the collection path 111a was evaluated. The results are shown in Table 1.

Table 1 shows the weight ratio of the waste developer to the waste toner in the recovery path 111a and the weight ratio of the waste carrier on the recovery path 111a for two samples of each color of waste developer of yellow, cyan, magenta, and black. It is an evaluation result showing the relationship with the occurrence of toner clogging in the developer discharge port 111b or the connection pipe 111c. The weight of the waste toner and waste carrier in the waste developer is obtained by measuring the weight of the waste developer (waste toner and waste carrier) and then sucking the waste developer through a 795 mesh to measure the weight of the waste carrier. and calculated.

According to Table 1, when the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a is 5% or more, the toner clogging does not occur on the collection path 111a. For this reason, the control unit 8 of the image forming apparatus 1 according to the present embodiment controls the discharge unit during non-image formation when the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a is less than a predetermined value. 46, a developer discharge process for discharging the developer from the developer container 41 is executed.

According to the above configuration, by discharging the developer from the developer container 41 through the discharge portion 46, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a can be increased. Fluidity of the agent can be preferably maintained. As a result, the waste developer can be smoothly transported in the collection path 111a, and toner clogging on the collection path 111a can be suppressed.

In particular, based on the evaluation results shown in Table 1, the control unit 8 of the image forming apparatus 1 according to the present embodiment determines that the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a is less than 5%. , the developer discharging process is executed. According to this configuration, the developer discharge process can be executed at appropriate timing. That is, it is possible to prevent the developer discharging process from being executed more than necessary, thereby improving the productivity of image formation and suppressing the consumption of the developer.

Next, conditions for executing developer discharge processing will be described. In this description, the configuration and operating conditions of the image forming apparatus 1 are as follows. The toner consumption per sheet is 3 mg, the transfer efficiency is 80%, the initial amount of developer in the developer container 41 is 300 g, the amount of developer in the developer container 41 is 350 g when stable, and the toner charge amount when stable is 30 μC/ is g.

When the amount of developer is stable, the amount of carrier discharged from the discharge section 46 of the developing section 40 is the same as the amount of carrier replenished from the container. For example, when the print rate is 5%, the amount of toner consumed is 15 mg (3 mg×5%) per sheet of A4 size paper, so the amount of toner replenished from the container is also 15 mg. Since the carrier filling rate in the container is 10%, the waste carrier amount is 1.5 mg.

The amount of waste toner is the amount of toner remaining on the surfaces of the photosensitive drum 21 and the intermediate transfer belt 31 without being transferred. If the transfer efficiency is 80%, the amount of waste toner is 3 mg with respect to 15 mg of toner consumed per sheet of A4 size paper.

Therefore, the weight ratio of the waste carrier to the waste toner in the waste developer in the recovery path 111a is 50% (1.5 mg/3 mg). Under this condition, according to Table 1, there is little possibility that toner clogging will occur on the collection path 111a, and it is considered that the developer discharge process does not have to be executed.

A case where the weight ratio of the waste carrier to the waste toner in the waste developer in the recovery path 111a is less than a predetermined value is when the developer (carrier) is not discharged from the developer container 41 for a long period of time. Examples of a long period in which the developer (carrier) is not discharged from the developer container 41 include (1) the period from the start of use of the image forming apparatus 1 until the amount of developer stabilizes, and (2) the amount of developer container 41 . corresponds to the case where the toner charge amount is less than a predetermined value.

In both cases, the volume of the developer in the developer container 41 is less than the stable volume, and the carrier is not discharged from the developer container 41 mechanically. Therefore, in these cases, it is necessary to forcibly discharge the carrier via the discharge portion 46 to increase the fluidity of the waste developer and suppress toner clogging on the collection path 111a.

Therefore, for example, regarding the period from the start of use of the image forming apparatus 1 to the stabilization of the amount of developer, the control unit 8 performs the developer discharging process every time a predetermined period elapses from the start of use of the image forming apparatus 1 . Run. During the period until the amount of developer is stabilized, the amount of carrier to be replenished in the developing container 41 is calculated from the amount of toner calculated from the cumulative printing rate, and the amount of carrier smaller than the amount of replenished carrier is discharged through the discharge section 46. By discharging the toner in a timely manner, it is possible to suppress toner clogging on the collection path 111a.

For example, when the amount of toner consumed per A4 size sheet at a printing rate of 1% is 3 mg, if the printing rate is 5%, 1.5 mg of carrier is supplied to the developer container 41 per A4 size sheet. be. As a result, if 0.15 mg or more and less than 1.5 mg of carrier per sheet is discharged through the discharge section 46, toner clogging on the collection path 111a can be suppressed. Therefore, it is possible to avoid a long period in which the developer (carrier) is not discharged from the developer container 41 during the period from the start of use of the image forming apparatus 1 until the amount of developer is stabilized. Further, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a can be increased, and the fluidity of the waste developer can be preferably maintained.

Further, for example, when the toner charge amount in the developing container 41 is less than a predetermined value, the control unit 8 measures the toner charge amount in the developing container 41, and when the toner charge amount is less than the predetermined value, Execute developer discharge processing.

Regarding the measurement of the toner charge amount, the image forming apparatus 1 further includes a voltage application section 12, a current detection section 13, and a density detection section 14, as shown in FIG.

The voltage application unit 12 includes, for example, a power supply unit and a control circuit (both not shown). The voltage applying section 12 is electrically connected to the developing roller 44 of the developing section 40 . The voltage applying section 12 applies a developing voltage to the developing roller 44 . Specifically, the voltage applying section 12 applies a developing voltage obtained by superimposing a DC voltage and an AC voltage to the developing roller 44 during development. The control unit 8 controls the application timing, voltage value, polarity, application time, and the like of the developing voltage to the developing roller 44 via the voltage applying unit 12 .

The current detection unit 13 detects a development current flowing between the development roller 44 and the photosensitive drum 21 when a development voltage is applied to the development roller 44 . The control unit 8 receives information regarding the amount of current flowing into the developing roller 44 detected by the current detection unit 13 . By integrating the development current i detected by the current detection unit 13 with the application time during development, the total charge amount Q for the developed toner image can be obtained. The controller 8 can measure the total charge amount Q of the toner image based on the development current i detected by the current detector 13 .

The density detection unit 14 is arranged to face the surface of the photosensitive drum 21 . The density detection unit 14 includes a reflective optical sensor having a light emitting unit including a light emitting element such as an LED (Light Emitting Diode) and a light receiving unit including a light receiving element such as a photodiode (neither is shown). . The light emitting unit irradiates the toner image transferred on the surface of the photoreceptor drum 21 with detection light at a predetermined angle. The light-receiving section receives the detection light that the light-emitting section irradiates toward the toner image and is reflected by the toner image.

The light-receiving section includes a specularly reflected light-receiving section that receives specularly reflected light out of the detection light reflected by the toner image, and a diffusely-reflected light-receiving section that receives diffusely reflected light. When there is no toner on the surface of the photoreceptor drum 21, the detection light emitted from the light emitting section is specularly reflected without being diffusely reflected by the toner, and much of it is incident on the specularly reflected light receiving section. As the amount of toner on the surface of the photosensitive drum 21 increases, more light is diffusely reflected by the toner, and the amount of light incident on the diffusely reflected light receiving portion gradually increases. In this manner, the density detection unit 14 irradiates the toner image with the detection light from the light emitting unit, reflects the light from the toner image, and receives the light at the light receiving unit (specularly reflected light receiving unit and diffusely reflected light receiving unit). The density of the toner image formed on the surface of the photosensitive drum 21 is detected based on the detection light.

Note that the density detection unit 14 may be configured to face the surface of the intermediate transfer belt 31 and detect the density of the toner image primarily transferred onto the surface of the intermediate transfer belt 31 .

The toner weight M of the toner image formed on the surface of the photoreceptor drum 21 can be estimated by detecting the density of the toner image with the density detection unit 14 and converting it into weight. For example, a predetermined table or the like showing the relationship between the output value of the density detection unit 14 and the toner weight M is pre-stored in the storage unit or the like and used so that the control unit 8 can detect the exposure detected by the density detection unit 14. Based on the density of the toner image formed on the surface of the body drum 21, the toner weight M of the toner image can be measured.

Then, the controller 8 can measure the toner charge amount Q/M in the developing container 41 based on the total charge amount Q and the toner weight M of the toner image.

When the toner charge amount in the developer container 41 is less than a predetermined value, that is, when the toner charge amount in the developer container 41 is lower than the stable toner charge amount, it becomes difficult for the carrier to be discharged from the developer container 41 . For example, as described above, when the toner charge amount in the stable state is 30 μC/g and the toner charge amount in the developer container 41 is less than 30 μC/g, it becomes difficult for the carrier to be discharged from the developer container 41 .

As a result, for example, when the amount of toner consumed per sheet at a print rate of 1% is 3 mg, if the print rate is 5%, the discharge section discharges 0.15 mg or more and less than 1.5 mg of carrier per sheet. By discharging via 46, toner clogging on the collection path 111a can be suppressed. Therefore, when the toner charge amount of the developer container 41 becomes less than a predetermined value, it is possible to avoid a long period in which the developer (carrier) is not discharged from the developer container 41 . Further, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a can be increased, and the fluidity of the waste developer can be preferably maintained.

Further, by using the current detection section 13 and the density detection section 14 as described above, it becomes possible to easily measure the toner charge amount in the developing container 41 .

With respect to the developing section 40 including the discharging section 46 and the regulating section 43c configured as described above, the control section 8 controls the rotation of the second conveying member 43 during image formation during the developer discharging process. Rotate in the opposite direction or rotate at high speed. As a result, the developer in the discharge portion 46 can be discharged from the developer discharge port 46a. For example, in the case of a configuration in which approximately 0.4 g of carrier can be discharged by rotating the second conveying member 43 once in the opposite direction, approximately 2600 sheets are required to discharge 0.15 mg of carrier per sheet. The second conveying member 43 may be rotated in the opposite direction at a frequency of once per cycle.

Further, it is more preferable that the amount of reverse rotation of the second conveying member 43 is set to 1 round or more and 1.5 rounds or less under the conditions of a predetermined print rate and a predetermined execution frequency of the developer discharging process.

For example, if the toner consumption per sheet at a print rate of 1% is 3 mg, and 1,000 sheets of paper with a print rate of 2% are printed, the toner consumption during the printing of those 1,000 sheets is 6 g. is. That is, the amount of toner replenished from the container to the developing section 40 during that time is 6 g, and if the carrier filling rate in the container is 10%, the amount of waste carrier from the developing section 40 is 0.6 g. For example, in the case of a configuration in which 0.4 g of carrier can be discharged by rotating the second conveying member 43 once in the opposite direction, the maximum value of rotation is 1.5 turns (=0.6 g).

If the amount of reverse rotation is less than one revolution, the amount of developer discharged from the discharge portion 46 is small, and the fluidity of the waste developer in the collection path 111a cannot be maintained favorably. If the amount of reverse rotation exceeds 1.5 rounds, too much developer is discharged from the discharge portion 46 and the amount of developer decreases relative to the initial amount of developer in the developer container 41 .

The amount of reverse rotation of the second conveying member 43 was evaluated. In this evaluation, the configuration and operating conditions of the image forming apparatus 1 are as follows: print rate per sheet is 2%, printable number of sheets is 10000 sheets, operating environment is temperature 32.5° C., humidity 80%. Then, (1) the developer discharge process is not executed, (2) the developer discharge process is executed by rotating the second conveying member 43 in reverse by 1.2 revolutions, and (3) the reverse rotation of the second conveying member 43 is executed. Printing evaluation was performed under three conditions of executing the developer discharging process for 2.0 revolutions.

As a result of the above printing evaluation, in the case of (1), sufficient carrier was not discharged, and when the number of printed sheets was 8500, toner clogging occurred in the connection pipe 111c of the collection unit 11, and the collection member 115 in the collection path 111a was locked. bottom. In the case of (2), the reverse rotation of the second conveying member 43 is 1.2 rounds, 0.48 g of carrier is discharged, and 10,000 sheets of printing are completed without toner clogging on the collection path 111a. bottom. In the case of (3), the reverse rotation of the second conveying member 43 is 2.0 rounds, 0.8 g of carrier is discharged, the developer amount is reduced, and it depends on the form of the conveying member in the developing section 40. Image unevenness occurred on the paper.

By setting the amount of reverse rotation of the second conveying member 43 to be 1 turn or more and 1.5 turns or less, the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a is maintained at, for example, 10% or more. becomes possible. Thereby, the fluidity of the waste developer can be preferably maintained. Further, the waste developer can be smoothly transported in the recovery path 111a, and it is possible to suppress toner clogging on the recovery path 111a.

In addition, when the printing rate on the paper is high, the amount of developer (carrier) replenished from the container to the developing container 41 increases, so the amount of developer in the developing container 41 tends to increase. On the other hand, when the printing rate is low, the amount of developer (carrier) supplied from the antenna to the developing container 41 is small, so the amount of developer in the developing container 41 is difficult to increase.

Therefore, the control unit 8 changes the rotation condition of the second conveying member 43 based on the print rate for the paper. For example, the control unit 8 changes the frequency of rotating the second conveying member 43 in the reverse direction or changes the frequency of rotating at high speed. According to this configuration, the amount of developer in the developer container 41 is constant regardless of the printing rate for the paper. As a result, a suitable amount of developer (carrier) is discharged through the discharge section 46, and the weight ratio of the waste carrier to the waste toner in the waste developer in the collection path 111a can be increased. .

In addition, when the toner does not contain titanium oxide as an external additive, the fluidity of the toner is lowered. Therefore, when the toner does not contain titanium oxide as an external additive, executing the developer discharging process with the above configuration is more effective in favorably maintaining the fluidity of the waste developer in the collection path 111a. is. That is, when the toner does not contain titanium oxide, the developer is discharged from the developer container 41 through the discharge portion 46, thereby increasing the weight ratio of the waste carrier to the waste toner in the waste developer. Thereby, it is possible to preferably maintain the fluidity of the waste developer in the collection path 111a.

Although the embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention.

For example, in the above-described embodiment, the image forming apparatus 1 is a so-called tandem-type image forming apparatus for color printing, in which images of a plurality of colors are sequentially superimposed and formed. is not. The image forming apparatus may be a non-tandem type image forming apparatus for color printing, an image forming apparatus for monochrome printing, or an image forming apparatus that does not use an intermediate transfer belt.

INDUSTRIAL APPLICABILITY The present invention can be used in image forming apparatuses.

REFERENCE SIGNS LIST 1 image forming apparatus 8 control section 11 recovery section 12 voltage application section 13 current detection section 14 density detection section 20 image forming section 21 photoreceptor drum (image carrier)
23 drum cleaning unit 30 transfer unit 31 intermediate transfer belt (image carrier)
34 belt cleaning section 40 developing section 41 developing container 42 first conveying member 43 second conveying member 43c regulation section 44 developing roller (developer carrier)
46 Discharge Portion 46a Developer Discharge Port 111 Housing 111a Recovery Path 111b Waste Developer Discharge Port 111c Connection Pipe 112 Developer Disposal Pipe 112a Developer Disposal Path 113 First Toner Disposal Pipe 113a First Toner Disposal Path 114 Second Toner Disposal Pipe 114a Second toner disposal path 115 Recovery member 412 First transport chamber 412a Developer supply port 413 Second transport chamber 414 First communication portion 415 Second communication portion 461 Discharge blade f1 First direction f2 Second direction S Paper

Claims (9)

an image carrier carrying a toner image on its surface;
a developing container containing a two-component developer containing a toner and a carrier, a developer bearing member carrying the developer in the developing container, and a discharge section discharging excess developer from the developing container; a developing unit that develops the electrostatic latent image formed on the surface of the image carrier with the toner to form the toner image;
a cleaning unit for removing the toner remaining on the surface of the image carrier;
a developer disposal path through which the waste developer discharged from the discharge section is transported and a toner disposal path through which the waste toner removed by the cleaning section is transported; a recovery unit that recovers the waste developer including the waste toner and the waste carrier through a recovery path;
a control unit that controls operations of the image carrier, the developing unit, the cleaning unit, and the recovery unit;
with
At least a portion of the recovery path has a portion with greater flow resistance than the toner disposal path,
When the weight ratio of the waste carrier to the waste toner in the waste developer in the recovery path is less than a predetermined value, the control unit removes the toner from the developer container through the discharge unit during non-image formation. An image forming apparatus that executes a developer discharging process for discharging developer. 2. The image according to claim 1, wherein the controller measures the amount of toner charge in the developer container, and executes the developer discharge process when the amount of toner charge is less than a predetermined value. forming device. a current detection unit for detecting a development current flowing between the developer carrier and the image carrier when a development voltage is applied to the developer carrier;
a density detection unit that detects the density of the toner image formed on the surface of the image carrier;
with
The control unit
A total charge amount of the toner image is measured based on the development current detected by the current detection section, and a toner weight of the toner image is measured based on the density of the toner image detected by the density detection section. 3. The image forming apparatus according to claim 2, wherein the toner charge amount is measured based on the total charge amount and the toner weight of the toner image. 4. The image forming apparatus according to any one of claims 1 to 3, wherein the control section executes the developer discharging process every time a predetermined period elapses from the start of use of the image forming apparatus. . The developing unit is
a first transfer chamber and a second transfer chamber arranged in parallel in the developer container and communicating with each other at both ends in the longitudinal direction;
a first conveying member rotatably supported in the first conveying chamber about an axis extending in the longitudinal direction and conveying the developer while agitating it in a first direction along the axial direction;
A second conveying device that is rotatably supported in the second conveying chamber about an axis extending in the longitudinal direction and conveys the developer while agitating the developer in a second direction opposite to the first direction along the axial direction. a member;
the developer carrier carrying the developer in the second transport chamber on its surface;
a developer supply port through which the developer is supplied into the developer container;
A developer outlet through which the developer is discharged from the developer container is provided downstream of the downstream end of the second transport chamber in the second direction and connected to the second transport chamber. a discharge portion in which a second conveying member extends continuously and the developer in the second conveying chamber is conveyed toward the developer discharge port;
a regulating portion formed on the second conveying member in the second conveying chamber so as to face a connecting portion between the second conveying chamber and the discharging portion, the regulating portion regulating movement of the developer toward the discharging portion; ,
with
The controller rotates the second conveying member in a direction opposite to the rotation of the second conveying member during image formation, or rotates the second conveying member at a high speed during the developer discharging process. The image forming apparatus according to any one of claims 1 to 4. 6. The image forming apparatus according to claim 5, wherein the control section changes the rotation condition of the second conveying member based on the printing rate for the recording medium. 2. The control unit executes the developer discharging process when a weight ratio of waste carrier to waste toner in the waste developer in the collection path is less than 5%. The image forming apparatus according to claim 6 . The image carrier is
a photosensitive drum carrying on its surface the toner image formed by the developing unit;
an intermediate transfer belt on which the toner image carried on the photosensitive drum is primarily transferred;
including
The cleaning unit
a drum cleaning unit for removing the toner remaining on the surface of the photoreceptor drum;
a belt cleaning unit for removing the toner remaining on the surface of the intermediate transfer belt;
including
The recovery unit is
the developer disposal path extending from the discharge section of the development section and carrying the waste developer;
a first toner disposal path that extends from the drum cleaning unit and conveys the waste toner;
a second toner disposal path that extends from the belt cleaning unit and conveys the waste toner;
the recovery path where the developer disposal path, the first toner disposal path, and the second toner disposal path merge;
8. The image forming apparatus according to any one of claims 1 to 7, comprising: 9. The image forming apparatus according to claim 1, wherein the toner does not contain titanium oxide as an external additive.

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