JP2022167059A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that is reduced in cost and size and can prevent the occurrence of density unevenness in an image.SOLUTION: An image forming apparatus 1 comprises: a developer container; a first conveying member and a second conveying member; a developing roller; a voltage application unit 12; a current detection unit 13; a driving unit 11; and a control unit 8. The first conveying member and second conveying member are rotatably supported in the developer container, convey, while stirring, developer along an axial direction of rotation, and circulate the developer in the developer container. The control unit 8 predicts the amount of developer attached to a surface of the developing roller based on the amount of current flowing into the developing roller during application of developing voltage, the amount of current detected by the current detection unit 13, and controls the driving unit 11 according to a result of prediction to change the rotation speed of the first conveying member and second conveying member.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus.

In electrophotographic image forming apparatuses such as copiers and printers, toner is attached to an electrostatic latent image formed on the surface of an image carrier such as a photosensitive drum, and then developed. Imaging devices are widely available. In the developing section, in order to continuously form a uniform image, the developer containing the toner accommodated inside the developing container is conveyed while being agitated within the developing container.

An image forming apparatus is often provided with a conveying member (for example, a conveying screw) that conveys developer by rotating inside a developer container. Due to the rotation of the conveying member, density unevenness may occur in the formed image. Japanese Patent Application Laid-Open No. 2002-200001 discloses an example of a conventional technique for suppressing the occurrence of image density unevenness caused by the rotation of a conveying member.

A conventional image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-200003 includes a screw that rotates to convey a developer, a detecting means that detects the density of an image to be formed, and a screw based on a change in density detected by the detecting means. A determination unit for determining density unevenness, and a development condition changing unit for changing development conditions when density unevenness due to a screw is determined. Thereby, it is possible to determine the occurrence of density unevenness due to the screw, and it is possible to suppress the occurrence of density unevenness due to the screw by changing the development conditions.

JP 2006-106565 A

However, in the case of the prior art, there is a problem in that a detecting means composed of, for example, a reflective sensor is provided separately from the developing section in order to detect the density of the formed image. As a result, there is a concern that the cost and size of the image forming apparatus will increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of suppressing the occurrence of density unevenness in an image with a structure that is low in cost and small in size. and

In order to solve the above problems, the image forming apparatus of the present invention includes a developer container, a developer conveying member, a developer carrier, a voltage application section, a current detection section, a drive section, a control section, Prepare. The developer container accommodates developer containing toner to be supplied to the image carrier. The developer conveying member is rotatably supported in the developer container, conveys the developer along the axial direction of rotation while agitating the developer, and circulates the developer in the developer container. The developer carrier faces the image carrier and is rotatably supported by the developer container, and supplies the toner in the developer container to the image carrier. The voltage application section applies a development voltage to the developer carrier. The current detector detects the amount of current flowing into the developer carrier when the developing voltage is applied. The driving section rotates the developer conveying member and the developer carrier. The control section controls the voltage applying section and the driving section. The control section predicts the amount of developer adhering to the surface of the developer carrier based on the amount of current detected by the current detection section, controls the driving section according to the prediction result, and Change the rotational speed of the developer conveying member.

According to the configuration of the present invention, it is possible to secure an amount of developer on the surface of the developer carrying member that enables formation of a suitable image without density unevenness without separately providing a dedicated sensor. Therefore, it is possible to suppress the occurrence of density unevenness in an image with a configuration that achieves cost reduction and miniaturization.

1 is a schematic cross-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 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. 4 is a graph showing the relationship between the amount of developer on the surface of the developing roller and the amount of current flowing into the developing roller when a developing voltage is applied.

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 cross-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 cross-sectional front view of the periphery of 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 on the surface of the photosensitive drum 21 . The developing unit 40 supplies toner to the electrostatic latent image and develops it to form a toner image. 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 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 an intermediate transfer member that is rotatably supported in a predetermined direction (counterclockwise in FIG. 1) and onto which the toner images formed by 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).

The image forming apparatus 1 further includes a driving section 11, a voltage applying section 12, and a current detecting section 13, as shown in FIG.

The drive unit 11 includes, for example, a motor and a control circuit (both not shown). The motor of the driving section 11 is connected to a first conveying member 42, a second conveying member 43, and a developing roller 44 of the developing section 40, which will be described later. The drive unit 11 can rotationally drive the first conveying member 42 , the second conveying member 43 , and the developing roller 44 . The control unit 8 controls the timing, rotation speed, rotation direction, rotation time, etc. of the first conveying member 42 , the second conveying member 43 , and the developing roller 44 via the driving unit 11 .

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 of the developing section 40 . 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 detector 13 detects the amount of current flowing into the developing roller 44 when the developing voltage is applied to the developing 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 .

Next, the configuration of the developing section 40 will be described using FIG. 4 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. Since the developing units 40 for each color have the same basic configuration, description of identification symbols representing each color and description of the constituent elements are omitted.

The developing section 40 supplies toner to the surface of the photoreceptor drum 21 . For example, the developing section 40 is detachable from the main body 2 of the image forming apparatus 1 . The developing unit 40 includes a developing container 41 , a first conveying member (developer conveying member) 42 , a second conveying member (developer conveying member) 43 , a developing roller (developer carrier) 44 , and a regulating member 45 . And prepare.

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 a developer to be supplied to the photosensitive drum 21, a two-component developer containing, for example, toner and magnetic carrier. The developer may be, for example, a magnetic one-component developer containing magnetic toner or a non-magnetic one-component developer.

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 pipe (not shown) is connected to the first transport chamber 412, and the developer is supplied through the developer supply pipe.

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.

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 structure of the first conveying member 42 and the second conveying member 43 is the same, and they have a configuration in which spiral blades are provided on the outer peripheral portion of the rotating shaft 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 second communicating portion 415 side to the first communicating portion 414 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 first communicating portion 414 side to the second communicating portion 415 side along the axial direction of rotation in the second conveying chamber 413 . .

The first communication portion 414 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 developer is transported from the first transport chamber 412 side toward the second transport chamber 413 side through the first communication portion 414 . The second communication portion 415 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 second communication portion 415 transports the developer from the second transport chamber 413 side toward the first transport chamber 412 side.

The developing roller 44 is arranged above the second conveying member 43 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 . Developing roller 44 carries a developer to be supplied to the surface of photoreceptor drum 21 in a region facing photoreceptor drum 21 . The developing roller 44 supplies the toner in the developing container 41 to the surface of the photosensitive drum 21 and develops the electrostatic latent image to form a toner image.

The regulating member 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 member 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 regulating member 45 extends over the entire area of the developing roller 44 in the axial direction. The regulating member 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 member 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 member 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.

FIG. 5 is a graph showing the relationship between the amount of developer on the surface of the developing roller 44 and the amount of current flowing into the developing roller 44 when the developing voltage is applied. For example, when the rotational speeds of the first conveying member 42 and the second conveying member 43 decrease, the amount of developer supplied to the developing roller 44 decreases, so the amount of developer on the surface of the developing roller 44 also decreases. As a result, when the development voltage applied to the development roller 44 is constant, the amount of current flowing into the development roller 44 during application of the development voltage is reduced. Therefore, the proportional relationship shown in FIG. 5 can be found between the amount of developer on the surface of the developing roller 44 and the amount of current flowing into the developing roller 44 when the developing voltage is applied. Note that the relationship shown in FIG. 5 is predetermined for each image forming apparatus.

When the rotational speeds of the first conveying member 42 and the second conveying member 43 further decrease, the amount of developer supplied to the developing roller 44 further decreases. For example, when the second conveying member 43 has spiral blades, the density unevenness is formed in a striped pattern in which light and shade alternate due to the pitch of the blades in the axial direction and the inclination of the blades with respect to the axial direction. sometimes called. As a result, the image formed on the sheet S also has stripe-like density unevenness.

In view of the above, the image forming apparatus 1 stores in advance a threshold value (see FIG. 5) for the amount of current flowing into the developing roller 44 when the developing voltage is applied, at which the screw pitch unevenness may occur. Then, the controller 8 of the image forming apparatus 1 according to the present embodiment controls the amount of developer adhering to the surface of the developing roller 44 based on the amount of current flowing into the developing roller 44 when the developing voltage is applied, which is detected by the current detecting unit 13 . Predict quantity. Further, the control section 8 controls the drive section 11 to change the rotational speeds of the first conveying member 42 and the second conveying member 43 according to the prediction result. That is, the control unit 8 rotates the first conveying member 42 and the second conveying member 43 at a rotation speed at which screw pitch unevenness does not occur.

Table 1 shows the relationship between the rotational speed of the first conveying member 42 and the second conveying member 43, the amount of current flowing into the developing roller 44 when the developing voltage is applied, and the presence or absence of screw pitch unevenness on the surface of the developing roller 44. It is an example. As for the configuration and operating conditions of the image forming apparatus 1, the outer diameter of the first conveying member 42 and the second conveying member 43 is 13 mm, and the screw pitch is 30 mm. The developing roller 44 has an outer diameter of 16 mm and a rotational speed of 450 rpm. The developing voltage applied to the developing roller 44 is DC of 400 V, AC of 1000 Vpp, 6 kHz, and a duty of 50%.

According to Table 1, the threshold for the amount of current flowing into the developing roller 44 when the developing voltage is applied is set to 10 mA, and the rotational speeds of the first conveying member 42 and the second conveying member 43 are set to a rotational speed at which the amount of current is 10 mA or more. It can be seen that screw pitch unevenness does not occur on the surface of the developing roller 44. FIG.

However, when the rotational speeds of the first conveying member 42 and the second conveying member 43 become high, the mixability of the existing developer in the developer container 41 and the newly supplied developer deteriorates, and the stress of the developer decreases. In addition, there is a possibility that problems such as component deterioration and toner sticking may occur due to the heat generated due to the rotational drive.

Therefore, it is desirable that the rotational speeds of the first conveying member 42 and the second conveying member 43 be as low as possible. That is, according to Table 1, if the rotational speeds of the first conveying member 42 and the second conveying member 43 are set to a rotational speed at which the amount of current flowing into the developing roller 44 when the developing voltage is applied is 10 mA, the surface of the developing roller 44 In addition, the rotational speed of the first conveying member 42 and the second conveying member 43 can be set to the lowest rotational speed.

According to the above configuration, it is possible to secure an amount of developer on the surface of the developing roller 44 that can form a suitable image without density unevenness without providing a separate dedicated sensor. Therefore, it is possible to suppress the occurrence of density unevenness in an image with a configuration that achieves cost reduction and miniaturization.

Specifically, for example, the amount of current that flows into the developing roller 44 when the developing voltage is applied is initially set to 11 mA. On the other hand, the first threshold of the current amount is set to 10 mA, and the second threshold, which is higher than the first threshold, is set to 12 mA.

For example, according to Table 1, if the amount of current that flows into the developing roller 44 when the developing voltage is applied is 8 mA, which is lower than the first threshold value of 10 mA, there is a possibility that screw pitch unevenness will occur on the surface of the developing roller 44 . Therefore, when the amount of current flowing into the developing roller 44 when the developing voltage is applied is lower than a predetermined first threshold value (for example, 10 mA in Table 1), the control unit 8 controls the first conveying member 42 and the second conveying member 43. Increase rotation speed. According to this configuration, it is possible to suppress the occurrence of screw pitch unevenness, that is, image density unevenness.

Further, according to Table 1, screw pitch unevenness does not occur on the surface of the developing roller 44 if the amount of current flowing into the developing roller 44 when the developing voltage is applied is 10 mA or more. However, if the rotational speeds of the first conveying member 42 and the second conveying member 43 become higher than necessary, the above-mentioned problems will occur, so it is desirable that the rotational speeds be lower. Therefore, when the amount of current flowing into the developing roller 44 when the developing voltage is applied is higher than a predetermined second threshold (for example, 12 mA in Table 1), the controller 8 controls the first conveying member 42 and The rotation speed of the second conveying member 43 is decreased. According to this configuration, screw pitch unevenness does not occur on the surface of the developing roller 44, and the rotational speeds of the first conveying member 42 and the second conveying member 43 can be set as low as possible.

In addition, every time the cumulative drive time of the developing roller 44 elapses for a predetermined time, the control unit 8 controls the amount of current flowing into the developing roller 44 when the developing voltage is applied during non-image formation, so that the developing roller 44 adheres to the surface of the developing roller 44 . Predict dosage. According to this configuration, it is possible to periodically take measures to suppress the occurrence of image density unevenness. Therefore, it is possible to continue preferable image formation.

Note that the prediction of the amount of developer adhering to the surface of the developing roller 44 based on the amount of current flowing into the developing roller 44 when the developing voltage is applied may be performed during calibration of the image forming apparatus 1 which is periodically performed. , once a day, or once every few days.

The developer conveying member rotatably supported in the developer container 41 is composed of a first conveying member 42 and a second conveying member 43 that convey the developer in opposite directions. According to this configuration, in the developing section 40 having a structure including two developer conveying members, that is, the first conveying member 42 and the second conveying member 43, a suitable image without density unevenness can be obtained without separately providing a dedicated sensor. can be secured on the surface of the developing roller 44. The number of developer conveying members may be one, or three or more.

Also, the developer is a two-component developer containing a magnetic carrier and a toner. It is known that when a two-component developer is used as the developer, density unevenness is likely to occur in the formed image due to rotation of a conveying member that conveys the developer by rotating in the developer container. Therefore, according to the above configuration, even when a two-component developer is used as the developer, the amount of the developer capable of forming a suitable image without density unevenness is It can be secured on the surface of the developing roller 44 . Therefore, it is possible to suppress the occurrence of density unevenness in an image with a configuration that achieves cost reduction and miniaturization.

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 image forming apparatus for color printing or an image forming apparatus for monochrome printing.

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

REFERENCE SIGNS LIST 1 image forming apparatus 2 main body 8 control unit 11 driving unit 12 voltage application unit 13 current detection unit 20 image forming unit 21 photoreceptor drum (image carrier)
40 Developing Unit 41 Developing Container 42 First Conveying Member (Developer Conveying Member)
43 second conveying member (developer conveying member)
44 development roller (developer carrier)

Claims (6)

a developer container containing developer containing toner to be supplied to the image carrier;
a developer conveying member that is rotatably supported in the developer container, conveys the developer while agitating it along the axial direction of rotation, and circulates the developer in the developer container;
a developer carrier facing the image carrier and rotatably supported by the developer container to supply the toner in the developer container to the image carrier;
a voltage applying unit that applies a developing voltage to the developer carrier;
a current detection unit that detects the amount of current flowing into the developer carrier when the development voltage is applied;
a driving unit that rotationally drives the developer conveying member and the developer carrier;
a control unit that controls the voltage application unit and the driving unit;
with
The control unit
The amount of developer adhering to the surface of the developer carrier is predicted based on the amount of current detected by the current detection section, and the drive section is controlled according to the prediction result to detect the amount of developer conveying member. An image forming apparatus characterized by changing a rotation speed. 2. The image forming apparatus according to claim 1, wherein the controller increases the rotation speed when the amount of current is lower than a predetermined first threshold. 2. The image forming apparatus according to claim 1, wherein the controller reduces the rotation speed when the amount of current is higher than a predetermined second threshold higher than the first threshold. 3. The controller predicts the amount of developer based on the amount of current during non-image formation every time a cumulative drive time of the developer bearing member elapses for a predetermined period of time. Item 4. The image forming apparatus according to any one of Item 3. 5. The image according to claim 1, wherein the developer conveying member comprises a first conveying member and a second conveying member that convey the developer in directions opposite to each other. forming device. 6. The image forming apparatus according to claim 1, wherein the developer is a two-component developer containing a magnetic carrier and the toner.

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