JP2023025426A - Image forming apparatus - Google Patents

Abstract

To increase the rotation speed of a conveying screw during non-image formation compared with that during image formation to break a toner layer caused by a clearance part between a side face inside a developer container and a developer conveying screw, thereby preventing developer stain and white streaks.SOLUTION: An image forming apparatus has switching means that switches the developer circulation speed of a developer circulation member to at least two or more circulation speeds, and the switching means executes the switching of the developer circulation speed of the developer circulation member during non-image formation to switch the developer circulation speed of the developer circulation member so that the developer circulation speed of the developer circulation member becomes faster during non-image formation than that during normal image formation.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer using an electrostatic recording method or an electrophotographic method for developing an electrostatic image formed on an image carrier using a developer containing toner and carrier. It is about.

A developing device for developing an electrostatic latent image formed on an image carrier by an electrophotographic method or an electrostatic recording method using a one-component developer or a two-component developer has conventionally been provided with a developing sleeve. Many developing devices have been proposed and adopted.

The developing sleeve is generally rotatably supported in the opening of the developing device via bearings at both ends. The surface of the developing sleeve may be roughened by blasting or the like, or may be provided with grooves on the surface of the developing sleeve. Visualize the upper latent image.

Here, if the amount of developer on the surface of the developing sleeve is uneven, the density of the visualized image on the photoreceptor also becomes uneven, resulting in image problems. Therefore, it is desirable to make the amount of developer on the surface of the developing sleeve uniform, and it is common practice to uniformly regulate the amount of developer on the surface of the developing sleeve with a regulating member called a regulating blade.

Further, the developing device is generally provided with a developing container for containing the developer, and a conveying member such as a screw is disposed in the developing container. be transported.

By the way, in such a developing device, in the developer pool portion near the regulating blade, the developer flows at substantially the same speed as the portion where the flow of the developer is blocked by the regulating blade, following the rotation speed of the developing sleeve. A sheared surface is generated at the boundary between the portion to be conveyed and the portion to be conveyed. As a result, the toner is released due to the flow difference at the sheared surface, resulting in the formation of a soft toner layer. When this toner layer grows, it obstructs the gap between the regulating blade and the developing sleeve. As a result, the area where the toner layer has grown has a smaller amount of developer coated on the developing sleeve than other areas, resulting in a light image density.

In order to solve this problem, Japanese Patent Application Laid-Open No. 2002-100001 discloses a plurality of vibrating members for vibrating a regulating member that regulates the thickness of the developer layer on the developer carrier, and the plurality of vibrating members during non-image formation. A configuration has been proposed that has control means capable of executing vibration modes that vibrate at different times so as not to occur at the same time.

Further, in Japanese Patent Laid-Open No. 2002-100002, the difference between the static torque and the dynamic torque caused by turning on and off the developing sleeve, where the difference in torque is the largest, is used to change the sheared surface, thereby moving the toner layer greatly, and at that time, the regulation blade is vibrated. An invention characterized by adding

Further, in Patent Document 3, when the rotation speed Vsc of the conveying screw and the rotation speed Vsl of the developing sleeve are set, the rotation speed is changed so that (Vsc/Vsl) becomes smaller during non-image formation than during image formation. has been proposed.

JP-A-2009-93073 Japanese Patent Application Laid-Open No. 2009-93072 JP 2011-53451 A

However, the following new problems were found by the studies of the present inventors. In recent years, there is a tendency to use small particle size toner from the viewpoint of high image quality. Since the small-particle-size toner has a small electric charge per particle, the influence of the adhesion force to the carrier is relatively greater than the driving force of the electric field, and the separation of the toner from the carrier tends to be poor, resulting in a decrease in developability. In order to make full use of small particle size toner, it is necessary to reduce the adhesive force to the carrier to ensure developability. easier to be Hereinafter, a toner layer growing on a shear plane such as a boundary surface between a fluid layer of developer and a non-moving layer of developer is referred to as "non-moving layer toner". As described above, the transport screw agitates and transports the developer to circulate in the developer container. However, the clearance between the side surface of the developer container and the transport screw is divided into a portion where the developer transport screw transports and agitates the developer and a portion where the developer transport screw cannot transport and agitate the developer. A cross section occurs.

Therefore, separation of the carrier and the toner occurs at this shear plane, resulting in the formation of the non-moving layer toner. If a developer with different fluidity such as a replenished developer flows in there, the area where the developer conveying screw can be conveyed and agitated expands, and the non-moving layer toner collapses and is conveyed as a soft agglomerate. Agglomerates also transfer onto the image carrier, resulting in image defects such as stain-like black streaks (hereinafter referred to as development stains). An image defect such as a so-called white streak may occur.

For development stains and white streaks caused by such causes, the above-mentioned Patent Documents 1, 2, and 3, which aim to avoid the growth of the toner layer by removing the toner layer from the back side of the regulation blade, , could not satisfactorily solve this problem.

The present invention has been made in view of the above problems. An object of the present invention is to increase the rotational speed of the conveying screw during non-image formation compared with that during image formation, thereby breaking the toner layer caused by the clearance between the side surface of the developer container and the developer conveying screw, thereby enabling development. To provide an image forming apparatus capable of suppressing stains and white streaks.

In order to achieve the above object, an image forming apparatus according to one aspect of the present invention has the following configuration. That is, the image forming apparatus of the present invention rotates while carrying an image carrier on which an electrostatic latent image is formed and a developer containing toner, and the image carrier is statically positioned at a position facing the image carrier. A developer carrier for developing a toner image on an electrostatic latent image to form a toner image, a developer circulation member for circulating the developer, and a regulating member for regulating the thickness of the developer layer on the developer carrier. and a developing device comprising: a switching unit configured to switch the developer circulation speed of the developer circulation member between at least two circulation speeds, the switching unit configured to switch the developer circulation The developer circulation speed of the member is switched during non-image formation, and the developer circulation is performed so that the developer circulation speed of the developer circulation member is faster during non-image formation than during normal image formation. It is characterized by switching the developer circulation speed of the member.

According to the present invention, the rotation speed of the conveying screw is increased during non-image formation compared to that during image formation, thereby breaking the toner layer caused by the clearance between the side surface of the developer container and the developer conveying screw, thereby developing. Spots and white streaks can be suppressed.

1 is a schematic diagram of an image forming apparatus according to a first embodiment; FIG. 2 is a cross-sectional view showing the configuration of the developing device according to the first embodiment; FIG. FIG. 5 is a diagram showing the movement of developer on the back side of the regulating blade; It is a figure showing the control block diagram which concerns on 1st Embodiment. It is a figure showing the timing chart which concerns on 1st Embodiment. FIG. 3 is a diagram showing an interface between a non-moving layer and a fluidized layer that occurs between a developing container and a conveying screw; FIG. 10 is a diagram showing the relationship between the speed increase of the conveying screw and the collapse of the non-moving layer toner; 4 is a flowchart showing an example of control according to the first embodiment; 9 is a flow chart showing an example of control according to the second embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention according to the claims, and not all combinations of features described in the embodiments are essential for the solution of the present invention. do not have. The present invention can be implemented in various applications such as printers, various printing machines, copiers, facsimiles, and multi-function machines.

[First embodiment]
(Overall Configuration of Image Forming Apparatus)
First, the operation of the entire image forming apparatus will be described with reference to FIG. The Y station, M station, C station, and K station in the drawing are configured almost identically except that the toner colors used in the developing devices 1Y, 1M, 1C, and 1K are yellow, magenta, cyan, and black. In the following, the configuration and operation of image forming apparatuses Y, M, C, and K will be described in a general manner with respect to the image forming apparatuses whose constituent members are denoted by reference numerals omitting Y, M, C, and K at the end of the reference characters. explain.

A photosensitive drum 10 serving as an image carrier is rotatably provided, and the surface of the photosensitive drum 10 is uniformly charged by a charger 21 and modulated according to an information signal by an exposure device 22 such as a laser. exposed to light to form a latent image. The latent image is visualized as a toner image by the developing device 1 in a process described later. The visualized toner image is transferred onto a transfer belt 24 in a first transfer section 23 provided at each station. The toner image transferred onto the transfer belt 24 is conveyed to the second transfer portion 25 . After that, the toner conveyed to the second transfer unit 25 is transferred onto the medium 28, which is a recording material, and then the toner image is fixed on the medium 28 by the fixing device 27 to obtain an image. The untransferred toner on the photosensitive drum 10 and the toner remaining on the transfer belt 24 after fixing are removed by cleaning devices 26 and 26z. The toner in the developer consumed in image formation is replenished together with the carrier from a toner cartridge (not shown).

(Two-component developer)
Next, the developer D used in the first embodiment will be described. In the first embodiment, non-magnetic toner particles (toner) and magnetic carrier particles (carrier) are used, and the non-magnetic toner particles contain a binder resin, a colorant, and optionally other additives. It is a colored resin particle, and an external additive such as colloidal silica fine powder is externally added to the surface thereof. The non-magnetic toner particles used in the first embodiment are negatively chargeable polyester-based resin and have a volume average particle diameter of about 5 μm to 8 μm. The magnetic carrier particles are made of magnetic metal particles such as iron, nickel, and cobalt whose surfaces are oxidized, and have a volume average particle size of about 40 μm.

(Structure of developing device)
Next, the operation of the developing device 1 will be described with reference to FIG.

In the developing device 1 of the first embodiment, a developing sleeve 8 as a developer carrying member is placed in a developing container 2 containing a two-component developer containing a non-magnetic toner and a magnetic carrier. and a regulating blade 9 that is a developer regulating member that is installed on the surface of the developing sleeve 8 and regulates the layer thickness of the developer carried on the surface of the developing sleeve 8 .

Approximately the central portion of the developer container 2 is partitioned vertically into a developing chamber 3 and a stirring chamber 4 by a partition wall 7 extending in a direction perpendicular to the plane of the paper. ing.

First and second conveying screws 5 and 6 serving as circulation means for agitating and conveying the developer T and circulating it in the developing container 2 are arranged in the developing chamber 3 and the stirring chamber 4, respectively. The first conveying screw 5 is arranged at the bottom of the developing chamber 3 substantially parallel along the axial direction of the developing sleeve 8, and rotates to move the developer T in the developing chamber 3 in one direction along the axial direction. transport. The second conveying screw 6 is arranged at the bottom of the stirring chamber 4 substantially parallel to the first conveying screw 5 and conveys the developer T in the stirring chamber 4 in the direction opposite to the direction of the first conveying screw 5. .

In this way, the developer conveyed by the rotation of the first and second conveying screws 5 and 6 passes between the developing chamber 3 and the stirring chamber 4 through openings (communicating portions) at both ends of the partition wall 7. circulated. The developer in the first conveying screw portion is supplied from the development blade 9 and the opening of the partition wall 7 by driving the stirring screw 5 . The first and second conveying screws 5 and 6 have a screw structure in which stirring blades made of a non-magnetic material are provided in a spiral shape around a rotating shaft, and each screw diameter is φ20 mm. The pitch is 30 mm and the rotation speed is set to 600 rpm.

Further, the developing container 2 has an opening at a position corresponding to the developing region facing the photosensitive drum 10, and the developing sleeve 8 as a developer carrying member is partially exposed to the photosensitive drum 10 side at the opening. is rotatably arranged in the A gap (SD gap) between the developing sleeve 8 and the photosensitive drum 10 is about 250 μm. The developing sleeve 8 is made of a non-magnetic material, and a magnet roller 8' serving as magnetic field generating means is installed in the interior thereof in a non-rotating state. It has carrying poles S1, N1, N2, N3. Among them, the first magnetic pole N3 and the second magnetic pole N1, which are of the same polarity, are installed side by side inside the developing container 2, and a repelling magnetic field is formed between the poles. It is configured such that the developer is separated from the surface of the developing sleeve.

During development, the developing sleeve 8 rotates in the direction of the arrow shown in the figure, carries the two-component developer whose layer thickness is regulated by the magnetic brush cut by the regulating blade 9, and applies it to the photosensitive drum 10. , and a developer is supplied to the electrostatic latent image formed on the photosensitive drum 10 to develop the latent image. The regulating blade 9, which is an ear-cutting member, is formed of a non-magnetic member made of a plate-shaped aluminum or the like and extends along the longitudinal axis of the developing sleeve 8. placed on the side.

Both toner and carrier of the developer pass between the tip of the regulating blade 9 and the developing sleeve 8 and are sent to the developing area. By adjusting the gap between the regulating blade 9 and the surface of the developing sleeve 8, the amount of the developer magnetic brush held on the developing sleeve 8 to be cut is regulated, and the developer is transported to the developing area. quantity is adjusted. In the first embodiment, the regulating blade 9 regulates the developer coating amount per unit area on the developing sleeve 8 to 30 mg/cm 2 . Also, the peripheral speed ratio V of the developing sleeve to the photosensitive drum is assumed to be 175%. The rotation speed is set to 500 rpm.

As the developing bias used in the first embodiment, a developing bias in which an AC component and a DC component are superimposed is applied to the developing sleeve 8 by the developing bias applying means 11 . In the first embodiment, a blank pulse of a DC component in which the AC component is intermittently thinned out is provided. was set to 8 pulses. Also, the ratio of the electric field on the development side to the electric field on the recovery side (hereinafter referred to as Duty) was set to 50%.

(Mechanism of generation of toner aggregates)
When the image ratio of the output is low, the external additive of the toner tends to be embedded or separated, resulting in a high degree of cohesion. It is known that when the degree of aggregation of toner is high, agglomerates are likely to occur. FIG. 3 shows the flow of developer in the vicinity of the regulating blade. The developer in the vicinity of the developing sleeve is conveyed at a high speed, while the developer behind the regulating blade away from the developing sleeve is conveyed at a slow speed or is a non-moving layer. Since a sheared surface is generated, the toner deteriorates and free toner accumulates to form aggregates.

In particular, a pulverized toner containing a wax component can be produced at a relatively low cost compared to other toners such as polymerized toner, but the wax component tends to exist in the vicinity of the toner surface due to its production method. If the external additive of the toner is embedded or separated, the coefficient of friction between the toner particles tends to increase due to the effect of the wax component on the toner surface. As a result, the degree of cohesion of the toner is increased, and the toner tends to stick to each other. The areas where the toner aggregates have grown hinder the coating on the developing sleeve compared to other areas, and the amount of developer coated is reduced, resulting in a low density image only in those areas. Furthermore, when the toner aggregate grows and clogs between the regulation blade and the developing sleeve, a defective image such as band missing may occur.

Further, in recent years, there is a tendency to use small particle size toner from the viewpoint of high image quality. As described above, if the adhesive force is lowered to make full use of the small particle size toner, the toner and the carrier are more likely to be separated, so that the non-moving layer toner is likely to be generated on the sheared surface.

The clearance between the side surface of the developer container 2 and the conveying screws 5 and 6 is divided into a portion where the developer conveying screw 6 conveys and agitates the developer and a portion where the developer conveying screws 5 and 6 cannot convey and agitate the developer. , a shear plane occurs at its boundary. Therefore, the toner is liberated at this sheared surface, and as a result, the non-moving layer toner is also generated at places other than the regulating blade 9 . When a developer with different fluidity such as a replenished developer flows in there, the area where the developer conveying screws 5 and 6 can be conveyed and agitated expands, and the non-moving layer toner collapses and is conveyed as soft agglomerates. Then, the agglomerates are transferred to the image carrier 10, resulting in an image defect called development stains. An image defect such as streaks may occur.

(Dead layer breaking control)
In the first embodiment, control is performed to change the rotation speed of the developer conveying screws 5 and 6 during non-image formation so as to be faster than during image formation. First, FIG. 4 shows a control block diagram for carrying out the control performed in the first embodiment. Although the motor 1a for driving the developing sleeve 8 and the conveying screws 5 and 6 is common in the first embodiment, a configuration having a driving motor for each is also possible. Next, FIG. 5a shows one example of specific timing of control performed in the first embodiment. Here, control is performed to increase the rotation speed Vsc of the conveying screws 5 and 6 from V1 during image formation to V2 during post-rotation after image formation. Then, the rotating speed of the conveying screws 5 and 6 is increased, that is, the driving at V2 causes the fluidized layer of the developer between the conveying screws 5 and 6 and the container clearance portion to spread outward as shown in FIG. As the rotation speed increases, the developer vector to the interface increases. As a result, the effect of destroying the interface formed by V1 by the developer moving at the speed of V2 is exhibited.

As a result, when the conveying screw is driven at the rotational speed V1 during image formation, the aggregated toner portion on the interface of the non-moving layer becomes a fluidized layer and collapses.

In addition, as the timing of executing the non-moving layer breaking control during non-image formation, it is executed during pre-rotation before image formation as shown in FIG. is also possible. In this way, it is possible to carry out at any time during the pre-rotation, the paper interval, or the post-rotation. If the developer is not sufficiently agitated and circulated after executing the non-moving layer breaking control, the crushed aggregated toner is developed as it is and becomes a development stain. Image defects may occur. Therefore, it is more preferable to perform the post-rotation when the stirring and circulation time can be secured before the next image formation.

During image formation, Vsl is 500 rpm, V1 of Vsc is 600 rpm, and each rotation speed during non-image formation is set to 1.25 times. In the case of , Vsl is 625 rpm and V2 of Vsc is 750 rpm.

(Relationship between increased conveying screw speed and non-moving layer toner collapse)
Next, the relationship between the speed of the conveying screw and the non-moving layer toner breakdown will be described.

The method for verifying the effect of increasing the speed of the conveying screw is as follows. First, the developing container containing the developer is idled for 150 minutes at a temperature of 40° C. and a humidity of 60%, without consuming or replenishing the toner at the same rotational speed as in image formation. Accumulate.

Regarding the generation of the non-moving layer toner and the idling time, after rotating at the rotation speed of V2 for 2.5 seconds, it is returned to V1, and the number of development stains generated on the development sleeve 8 is observed with a line camera and the number is counted. do. At this time, the number of development stains counted indicates the crushing force of the non-moving layer toner when the roller is rotated at the rotation speed of V2. It was confirmed that the number of development stains generated in V1 was five, while the number of development stains generated in V2 increased according to the speed as shown in FIG.

The rotation speed and rotation time of V2 may be changed according to the production amount of the non-moving layer toner and product restrictions. In the first embodiment, V2: 125% rotation for 2.5 seconds, which can crush about four times as much non-moving layer toner as V1, is adopted.

(Control example)
The operation of the image forming apparatus employing the dead layer breaking control will be described with reference to the flowchart (FIG. 8). In the first embodiment, the speed-up control of the conveying screw is performed between sheets when a predetermined number of sheets have been passed and during post-rotation.

The power of the image forming apparatus is turned on (S000), and the user starts the image forming operation (S001).

At this time, the CPU in the main body of the image forming apparatus calls out the number of sheets (A4 landscape) N1 since the conveying screw speed-up control was performed last time (S002). Since the speed-up control of the conveying screw is also performed during the post-rotation, N1=0 at the start of the next image forming operation.

The predetermined number of sheets at this time is assumed to be 2000 sheets. It is determined whether N1 has reached a predetermined number (2000 in this embodiment) (S003). It is desirable that the predetermined number of sheets be appropriately optimized according to product specifications. If the predetermined number of sheets has not been reached, the image forming operation is continued, and the number of sheets N1 after carrying out speed-up control of the conveying screw is incremented by +1 (S011). When N1 reaches the predetermined number of sheets (S003), the image forming operation is temporarily stopped (S004), and the speed of the developer conveying screw is set to 125% (V2) for 2.5 seconds (regarding the normal speed as 100%). (S005). When the speed-up control for 2.5 seconds is completed, the image forming operation is resumed, and the count of the number of sheets N1 after the speed-up control of the conveying screw is cleared (S006). After that, the image forming operation is restarted (S007), and at the end of the job (S008), the speed-up control of the conveying screw is performed regardless of the number of sheets N1 after the speed-up control of the conveying screw is performed (S009).

This section describes the results of verification of actual equipment equipped with this control. 5000 sheets (A4) were intermittently tested on the actual machine, and the above control was performed between every 2000 sheets and at post-rotation after 5000 sheets. While the frequency of development spots was 0.23%, the frequency decreased to 0.04% when this control was performed. As described above, it was possible to suppress the occurrence of development stains by performing control to break up aggregates formed in the non-moving layer.

[Second embodiment]
Next, a second embodiment of the invention will be described. The basic configuration and operation of the image forming apparatus of the second embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations are denoted by the same reference numerals, and detailed descriptions thereof are omitted, and the characteristic points of the second embodiment are described below.

The difference from the first embodiment is that the trigger for carrying out the speed-up control of the conveying screw is not judged only by whether or not the predetermined number of sheets has been reached, but the environment in which the image forming operation is executed and the number of durable sheets of the developing container are determined. , and the duty of the image being passed. Since the speed-up control of the conveying screw is a control for suppressing the generation of the non-moving layer toner, the frequency of control is increased under conditions where the non-moving layer toner is likely to be generated, and conversely, under the conditions where the non-moving layer toner is less likely to be generated. If so, it is desirable to reduce the frequency of control implementation.

As described above, the non-moving layer toner is generated by separating the toner and the carrier. Since the toner adheres to the carrier by electrostatic force, the toner and the carrier are more likely to separate in a high-temperature, high-humidity environment where the toner charge amount is low. Further, if the image forming operation is continued while the image duty is low, the external additive on the surface of the toner is liberated and buried. That is, it is desirable to predict the generation state of the non-moving layer toner from the installation environment of the image forming apparatus, the image duty, and the number of durable sheets, and appropriately adjust the execution frequency of the speed-up control of the conveying screw.

(Control example)
The operation of the image forming apparatus employing the dead layer breaking control will be described with reference to the flowchart (FIG. 9). In the second embodiment, it is assumed that the speed-up control of the conveying screw is performed between sheets when a predetermined number of sheets are passed and during post-rotation. The determination flow of the predetermined number of sheets is shown below.

The power of the image forming apparatus is turned on (S100), and the user starts the image forming operation (S101).

At this time, the CPU in the main body of the image forming apparatus calls out the number of sheets (A4 landscape) N2 since the last execution of the conveying screw speed up control (S102). Since the speed-up control of the conveying screw is also performed during the post-rotation, N2=0 at the start of the next image forming operation.

Information from the environment sensor of the image forming apparatus is sent to the CPU to determine whether the environment is hot and humid. If the environment is judged to be in a hot and humid environment, a predetermined coefficient is applied to the execution frequency of speed-up control of the conveying screw. In the second embodiment, the coefficient is set to 0.7 when it is determined that the environment is hot and humid, and the coefficient is set to 1.0 when it is not determined to be hot and humid. At this time, it is desirable that the environment sensor is installed near the developer container so that the temperature and humidity of the developer can be detected.

Further, when the durability of the developer container exceeds 500,000 sheets, the frequency of speed-up control of the conveying screw is multiplied by a coefficient of 0.9, and if the durability of the developer container is 500,000 sheets or less, similarly 1.0. is multiplied by the coefficient of

Also, the average image duty of the image forming apparatus is called, and when the average image duty is 10% or less, a coefficient of 0.8 is applied to the speed-up control execution frequency of the conveying screw. If the average image duty exceeds 10% and is 20% or less, the frequency of carrying out speed-up control of the conveying screw is multiplied by a coefficient of 1.0. When the average image duty exceeds 20%, a factor of 2.0 is applied to the speed-up control execution frequency of the conveying screw.

It should be noted that it is desirable to optimize the coefficient of the execution frequency according to the specifications of the product.

At this time, when the default execution frequency of speed-up control of the conveying screw is set to 6000 sheets, in a hot and humid environment, the number of durable sheets of the developing container exceeds 500000 sheets, and the average image duty of the image forming apparatus is 5. %,
6000 sheets (default value) x 0.7 x 0.9 x 0.8 = 3024 sheets, and the predetermined number of sheets for speed-up control of the conveying screw is determined to be 3024 sheets (S103).

Next, it is determined whether N2 has reached the predetermined number of 3024 sheets (S106). Since the predetermined number of sheets has not been reached, the image forming operation is continued, and the number of sheets N2 after carrying out speed-up control of the conveying screw is incremented by +1 (S114). When N2 reaches the predetermined number of sheets (3024 sheets), the image forming operation is temporarily stopped (S107), and the speed of the developer conveying screw is set at 125% (V2 ) (S108). When the speed-up control for 2.5 seconds is completed, the image forming operation is resumed, and the count of the number of sheets N2 after the speed-up control of the conveying screw is cleared (S109). At the end of the image forming operation (S111), the speed-up control of the conveying screw is performed (S112) regardless of the number of sheets N2 after the speed-up control of the conveying screw is performed, and the speed-up control of the conveying screw is performed. After that, the count of the number of sheets N2 is cleared (S113).

As described above, by appropriately optimizing the execution frequency of speed-up control of the conveying screw according to the installation status of the image forming apparatus and the usage status of the user, a high-quality image forming apparatus free of defective images is provided. It becomes possible.

(Other embodiments)
The present invention is not limited to the above embodiments, and various modifications (including organic combinations of each embodiment) are possible based on the gist of the present invention, and they are excluded from the scope of the present invention. isn't it.

In the above embodiment, as shown in FIG. 1, the image forming apparatus using the intermediate transfer belt 41 has been described as an example, but the present invention is not limited to this. It is also possible to apply the present invention to an image forming apparatus having a configuration in which the paper P is brought into direct contact with the image carrier 3 in order for transfer.

1 developing device 1a motor 2 developing container 8 developing sleeve 9 regulating blade

Claims (2)

an image carrier on which an electrostatic latent image is formed;
a developer bearing member that bears and rotates a developer containing toner and develops the toner onto an electrostatic latent image of the image bearing member at a position facing the image bearing member to form a toner image; An image forming apparatus comprising: a developing device including a developer circulating member for circulating developer; and a regulating member for regulating the thickness of the developer layer on the developer carrier,
switching means for switching the developer circulation speed of the developer circulation member to at least two circulation speeds;
The switching means switches the developer circulation speed of the developer circulation member during non-image formation, and the developer circulation speed of the developer circulation member is higher during non-image formation than during normal image formation. An image forming apparatus, characterized in that the developer circulation speed of the developer circulation member is switched such that the developer circulation speed increases. 2. The image forming apparatus according to claim 1, wherein the timing at which the switching unit switches the developer circulation speed of the developer circulation member is determined from an installation environment of the image forming apparatus, the number of durable sheets, and an image duty. .

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