JP2002214892A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a toner-carrying performance and also a toner-stirring performance by improving a helical developer carrying member for an image forming apparatus, to rapidly restart an image forming operation, after a long period of rest of the image forming apparatus, and to efficiently obtain proper image quality. SOLUTION: In the image forming apparatus provided with a developing unit for carrying a developer layer, where an electrostatic latent image formed on a photoreceptor being a electrostatic latent image carrier, is carried on a developing sleeve as a developer carrier into a developing area, and then, developing the latent image, the apparatus is provided with a control means for detecting that the developer is left as it is for a long period in the developing unit, and then, controlling the helical developer carrying member and/or the stirring member in the developing unit so that they may be made in an active state in order to recover the charged quantity of the developer when it is determined that the developer has been left as it is, over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a developing device with improved toner charging performance.

[0002]

2. Description of the Related Art Conventionally used toner is a pulverized system with an irregular shape.To satisfy production efficiency in terms of energy and cost, due to the manufacturing machinery, the toner particle size must be reduced and the dispersion must be small. There was a limit to uniformity and uniformity, and it was impossible. In addition, it has been difficult to sufficiently meet the recent demand for higher image quality, in which it is essential to reduce the toner particle size.

[0003] 2. In order to solve such a problem, a polymerized toner produced by a polymerization method has a uniform shape and a uniform particle size distribution, and thus shows stable development and transfer characteristics, and is an effective means for high image quality. Things have come to light.

[0004]

However, when the particle size is reduced for higher image quality, the total surface area of the toner is significantly larger than the total surface area of the carrier. It takes a long time to increase, that is, the charge amount reaches a saturated charge amount at which a steady image can be formed.In other words, the rise of the charge is delayed, and problems such as toner scattering and image contamination called “fog” on an image background portion are caused. appear.

The present invention shortens the rise time of the toner charge to shorten the image forming time at the start, and also quickly recovers from the decrease in the charge amount after standing, thereby avoiding toner scattering and image fogging. An object is to obtain a high-quality image.

[0006]

This object is achieved by any of the following technical means (1) to (6).

(1) A developer layer in which an electrostatic latent image formed on a photoreceptor as an electrostatic latent image carrier is carried on a developing sleeve as a developer carrier is transported to a developing area to develop the image. In an image forming apparatus having a developing device for forming an image, a turbulent flow forming hole penetrated to provide a turbulent stirring function is provided in a part of a spiral blade of a spiral developer conveying member in the developing device. An image forming apparatus comprising:

(2) A developer layer in which an electrostatic latent image formed on a photoreceptor as an electrostatic latent image carrier is carried on a developing sleeve as a developer carrier is transported to a developing area to develop the image. In an image forming apparatus having a developing device for forming an image, a developer is left in the developing device for a long time, and when it is determined that the developing device is left for a long time, a helical developer conveying member in the developing device for recovering a developer charge amount. And / or a control unit for controlling the operation of the stirring member.

(3) The long-term leaving of the developer in the developing device is determined based on detection of a temperature decrease in the image forming apparatus or a temperature decrease in the fixing device of the image forming apparatus (2). Item 10. The image forming apparatus according to item 1.

(4) The image forming apparatus according to any one of (1) to (3), wherein the developer used in the image forming apparatus is a two-component developer including a toner and a carrier. .

(5) The toner has a number average particle size of 2 to 2.
The image forming apparatus according to item (4), wherein the thickness is 9 μm.

(6) The image forming apparatus according to (4) or (5), wherein a part or all of the developer is manufactured by a polymerization method.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of an embodiment of an image forming apparatus of the present invention in which an improved developing device is incorporated will be described with reference to a schematic configuration diagram of FIG.

An image forming apparatus 1 shown in FIG. 1 is an image forming apparatus of a digital system, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer material conveying unit D as a transfer material conveying unit. It is configured.

An automatic document feeder for automatically conveying a document is provided above the image reading section A.
The original placed on the original 1 is moved by the original transport roller 12 to the original 1.
The sheets are separated and conveyed, and the image is read at the reading position 13a. The document for which reading of the document has been completed is discharged onto the document discharge tray 14 by the document conveying roller 12.

On the other hand, the image of the document placed on the platen glass 13 is read in the form of a V-shape by a reading operation at a speed v of a first mirror unit 15 comprising an illumination lamp and a first mirror constituting a scanning optical system. Reading is performed by moving the second mirror unit 16 including the second mirror and the third mirror located at the speed v / 2 in the same direction.

The read image is formed on a light receiving surface of an image sensor CCD as a line sensor through a projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (brightness signal), and then A
After performing / D conversion and performing processing such as density conversion and filter processing in the image processing unit B, the image data is temporarily stored in the memory.

In the image forming section C, as an image forming unit, a drum-shaped photosensitive member 21 as an image carrier, a charging unit 22 for charging the photosensitive member 21 around the outer periphery thereof, a developing device 23 as a developing unit, A transfer conveyance belt device 45 as a transfer unit, a cleaning device 26 for the photoconductor 21 and a PCL (precharge lamp) 27 as a light removing unit are arranged in the order of operation. The photoreceptor 21 is formed by applying a photoconductive compound on a drum substrate. For example, an organic photoreceptor (OPC) is preferably used, and is driven to rotate clockwise in the drawing.

After the rotating photoreceptor 21 is uniformly charged by the charging means 22, an image exposure based on the image signal called from the memory of the image processing unit B is performed by the exposure optical system 30 as the image exposure means. Done. An exposure optical system 30 serving as an image exposure means serving as a writing means uses a laser diode (not shown) as a light emission light source, passes through a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35, and the optical path is bent by a reflection mirror 32 to perform main scanning. In this case, image exposure is performed on the photoconductor 21 at the position Ao, and a latent image is formed by rotation (sub-scan) of the photoconductor 21. In one example of the present embodiment, a character portion is exposed to form a latent image.

The latent image on the photosensitive member 21 is subjected to reversal development by a developing device 23 as a developing means as shown in the sectional view of FIG. 2, and a visible toner image is formed on the surface of the photosensitive member 21. You. In the transfer material transport section D, paper feed units 41 (A), 41 (B), and 41 serving as transfer material storage means in which transfer materials P of different sizes are stored below the image forming unit.
(C) is provided, and a manual paper feed unit 42 for performing manual paper feed is provided on the side, and the transfer material P selected from any of them is guided along the transport path 40 by the guide roller 43. The transfer material P is temporarily stopped by a pair of registration rollers 44 that corrects the inclination and the deviation of the fed and fed transfer material P, and then re-feeded.
0, the toner image on the photoreceptor 21 is guided by the pre-transfer roller 43a, the paper feed path 46, and the entrance guide plate 47 at the transfer position Bo by the transfer pole 24 and the separation pole 25 by the transfer conveyance belt 454 of the transfer conveyance belt device 45. The transfer material P is transferred onto the transfer material P while being placed and transported on the photoconductor 2.
The sheet is separated from one surface, and is conveyed to the fixing device 50 by the transfer conveying belt device 45.

The fixing device 50 has a fixing roller 51 and a pressure roller 52. By passing the transfer material P between the fixing roller 51 and the pressure roller 52, the toner is heated and pressurized. Fix it. The transfer material P on which the toner image has been fixed is discharged onto the discharge tray 64.

The above is a description of a state in which an image is formed on one side of the transfer material. The image forming apparatus 1 of the present embodiment performs reverse conveyance before discharging the transfer material P, and An image is formed on the back side and double-sided transfer can be performed. However, since the double-sided transfer is not directly related to the present invention, the description thereof is omitted.

Next, the improved developing device 23 incorporated in the present invention will be described with reference to the sectional view of FIG. 2 and the perspective view of the spiral developer conveying member of FIG.

A developing sleeve 232 as a developer carrier, a developer thickness regulating plate 233, a stirring wheel 234, a spiral are provided in the main body case 231 of the developing device 23 as a developing means with a certain clearance from the photosensitive member 21. Developer conveying member 2
The spiral developer conveying member 235 is provided with a spiral blade 236, and the spiral blade 236 is provided with a turbulent flow forming hole 239.

In this manner, the turbulent flow forming holes 239 are formed in the spiral blades 236 of the spiral developer transport member 235 in the developer transport path, and the function of transporting the developer in the axial direction is achieved. By having the function of turbulent stirring, the toner can be efficiently stirred and transported in a relatively short time.

In order to improve the image quality, it is necessary to reduce the diameter of the toner when adopting a small-diameter polymerized toner produced by a polymerization method in which the particle size and charge amount distribution of the toner are uniform, the dispersion is small, and the toner characteristics are excellent. As a result, the high agitation performance hardly hinders the increase in the required number of contacts with the carrier until the total surface area of the toner increases to reach the saturation charge amount and the charging rise time becomes longer. Was.

As another problem, when image formation is interrupted for a long time, the presence of weakly charged toner increases due to spontaneous discharge of the developer, and when image formation is restarted in this state, toner scattering or image background image formation may occur. Fogging and dirt are likely to occur.

In order to solve this, as shown in FIG. 1, the temperature inside the image forming apparatus 1 in the vicinity of the developing device 23 or the temperature of the fixing device 50 is detected by the detecting means 39 or 54, and as shown in the circuit diagram of FIG. As shown in the figure, when the temperature is low, the developer is judged to be in the state of being left for a long period of time, and in order to recover the decrease in the charge amount due to the long-term standing, the developer is stirred for a certain period of time and the charge amount is quickly raised to a normal value. A control means 80 for controlling the operation is provided. As a result, the spiral developer conveying member 235 and the stirring wheel 234 in the developing device 23 are controlled to automatically rotate, and the standby at the start of image formation is efficiently performed.

By the above means of the present invention, the agitating function of the developing device is strengthened, and when there is a high possibility that weakly charged toner is present in the developing device, the developing device is agitated to recover the charge amount. By performing the control, it becomes possible to avoid contamination inside the apparatus due to toner scattering at the time of resuming image formation and fogging contamination of the image background portion.

[0030]

EXAMPLE A live-action test was performed as follows.

(1) Among the toner and carrier used in the experiment, the toner is a polymerized toner having a number average particle size of styrene / acrylic 6.5 μm and a toner concentration of 4.0% by mass, and the carrier is a ferrite carrier (silicone). (Based resin coat, number average particle size 60 μm). In order to study the effect of the difference in toner particle size, 2/5/8/1
A toner having a number average particle diameter of 1 μm was also used.

(2) As an experimental machine for a live-action test, a modified Sioss 7065 manufactured by Konica Corporation (mono black digital copier / printer, compatible with 400 and 600 dpi,
(The laser beam diameter is 55 μm in main scanning and 80 μm in sub-scanning.)
And a continuous copy of an A3-size original having a printing rate of 5% in an environment of 20 ° C. and 50% RH. Here, dpi is 25.
It is a unit of resolution that indicates the number of dots that can be distinguished per 4 mm.

(3) Evaluation items are: a) toner scattering state, that is, presence or absence of toner contamination inside the machine mainly around the developing device; b) image background fogging state, that is, image formation with an A3-size printing rate of 5%. And b) the amount of toner charge measured by the blow-off method.

First, as a preliminary experiment prior to the present experiment, a single unit agitation test of each developing unit mounted on the image forming apparatus of the present invention and the image forming apparatus of the prior art was conducted as follows.

The developing sleeve 232 and the agitating wheel 234 are fixed without being operated, and only the spiral developer conveying member 235 (used in the present invention) and 235A (used in the conventional example shown in FIG. 4) are rotated in each developing unit 23. The drive rotation was performed at 300 rpm.

The above-mentioned carrier 600g is transferred to the spiral developer conveying members 235 and 235 in the developer conveying path in the developing device.
A, and then, the toner is charged almost uniformly first.
After the mass% was placed on the carrier described above, drive stirring was started. At each sampling time, a part of the developer in the developing device 23 was taken out and the toner charge amount was measured.

The charge amount was measured by the blow-off method as described above. FIG. 7 is a graph showing a change in the rise of the charge amount of the developer in the developing device 23 in the preliminary experiment, in which the horizontal axis represents the stirring time and the vertical axis represents the toner charge amount. That is, (1) in the developing device using the spiral developer conveying member 235A having the shape shown in FIG. 4, the saturation charge amount (about -45 μC / g) was reached after 5 minutes and 30 seconds as shown by the solid line.

(2) The turbulent flow forming hole 23 is formed in the spiral blade 236.
In the developing device 23 used in the present invention having the spiral developer conveying member 235 having the shape shown in FIG. 3 with the opening 9 opened, as shown by the dotted line, the saturated charge amount (about -45 μC / g) was reached after 3 minutes. . The charge rising time was significantly faster than that of the conventional shape, and the improvement of the stirring performance was confirmed.

Next, a description will be given of a comprehensive experiment in which the entire image forming apparatus is driven. In this experiment, 30,000 copies were continuously made, and after that, in a state where the apparatus was left stopped for 12 hours (hrs), the dependence of the difference in the shape of the spiral developer transport member on the recovery performance of the decrease in the charge amount after being left was determined. The dependence of the toner number average particle diameter was examined.

That is, when the image forming operation is stopped and stopped for a long time, and then restarted, the charge amount recovery time due to the difference in the shape of the spiral developer transport member and the presence or absence of fogging in the image background are investigated. Dependence of recovery time on toner particle size,
Were compared.

The determination criterion after the standing can be determined based on any one of the internal temperature provided near the developing device 23 in the image forming apparatus 1 and the temperature of the fixing roller 51 of the fixing device 50.

In this embodiment, the temperature of the fixing roller 51 is monitored by a thermocouple.

Actually, it was confirmed that the fixing roller 51 was left at room temperature of 20 ° C. when left overnight (12 hours) after continuous copying.

However, in the experiment of the embodiment of the present invention, an experiment was conducted in a severe case in which the image formation (continuous copying of 30,000 sheets) was allowed to stand for 12 hours and then restarted.

As a toner charge recovery operation, the developing unit 23 was rotated for a set time of about 10 minutes. In this embodiment, the spiral developer conveying members 235, 235A, 235B, 23
5C was rotated at 300 rpm.

The evaluation was performed as follows. a) The toner charge amount was obtained by collecting the developer from the developing sleeve 232 at each stirring time and measuring the toner charge amount by the blow-off method as described above. b) Image background fogging is carried out at the minimum required number of A3-size originals with a blackening rate (or printing rate) of 5% for each stirring time, and the background fogging state is visually evaluated. It was observed under magnification.

The agitating performance and the developer transporting performance due to the difference in the shape of the spiral developer transporting member are such that the transporting state in the developer agitating and transporting portion in the developing device is not uniform (a stagnation and stagnation occurs at a specific place, or Check the flow of the developer by moving the entire drive system of the developer to see if there is a shortage of developer supply. Also, set the developer to the above-mentioned actual machine (Sonicas 7065 remodeled machine manufactured by Konica Corp.) Halftone and solid black image formation were performed, and it was confirmed whether or not non-uniform density occurred due to uneven conveyance on the image. Table 1 shows the results.

[0048]

[Table 1]

The criteria for the overall evaluation in Table 1 were as follows. ：: The flow of the developer is uniform, smoothly circulates, and is uniformly distributed. There is no back surface contamination of the image, and the image density is kept uniform.

Δ: Detention of the developer (development of the developer) is observed in part, but the non-uniformity of the developer is still small, and the developer is conveyed in the developing device and the image is contaminated and the image density is not uniform. No effect yet.

×: Large retention and insufficient portion of the developer are clearly recognized in the developing device, and toner scattering due to insufficient stirring performance, spilling of the developer from the developing device, and uneven image density due to uneven transport to a part of the developing sleeve. And at least one problem of image contamination.

Further, regarding the transport performance and the stirring performance,
The developer flow was visually observed, and the four types of spiral developer conveying members were ranked in the first to fourth ranks to evaluate the superiority. 1) In the case of the conventional shape, the stirring performance was the fourth lowest and the transport performance was the best first. 2) With the rod-shaped turbulence forming member, the stirring performance is 3
In terms of position and transfer performance, there was no difference from the conventional type, and it was the first place equivalent. 3) With the paddle-shaped turbulence forming member, the stirring performance was the highest at the top, but the transport performance was the worst at the fourth because the paddle greatly hindered the transport by the screw. 4) When the turbulent flow forming hole 239 is formed in the spiral blade portion of the spiral developer conveying member 235 of the present invention, the stirring performance is turbulent in the turbulent flow forming hole 239 and the turbulent flow forming hole 239 has the following characteristics.
The transfer performance was almost the same as that of the conventional type, with almost no hindrance to transfer by the screw.

Therefore, it can be understood that the present invention of three points is the most excellent in the total score (the smaller the score is, the better) of the above four types of kana and the two scores are combined.
In the second place, the conventional type and the paddle type with 4 points of the rod-shaped type, and the worse were 5 points with the same point (shown in parentheses in Table 1).

Further, the charge amount of the toner at each time due to the difference in the shape of the spiral developer conveying member was measured, and the relationship between the charge amount until reaching the saturated charge amount and the recovery time was as shown in the graph of FIG. . The time until the fog disappeared (disappeared) was also measured.

That is, the developer is kept for 12 hours after continuous copying.
The sample was allowed to stand as it was, and after the standing, the toner charge amount recovery status and the image background fog of the material according to the specifications described above were examined.

A conventional spiral developer conveying member 2 shown in FIG.
The spiral blade 236A of the spiral developer transport member in the developer transport path of 35A does not have a turbulent flow forming hole. In this case, the function of transporting the developer in the axial direction is main, and the stirring function is performed along the spiral. Since the movement is only a moving movement and is not a kind of aggressive turbulent stirring, the time to recover the charge amount is the longest (the fourth time) until the charge amount reaches the saturation charge amount 3.5.
It's been a minute. It was also confirmed that the background fog disappeared after 3.5 minutes.

Although the spiral developer transport member 235B with the rod-shaped turbulence forming member 237 shown in FIG. 5 is conventionally designed to improve the agitation property, the setting and mounting of the rod-shaped turbulence forming member 237 is difficult to process and assemble, and costs are reduced. Is high. But this is
The saturated charge amount was reached 2.7 minutes after the third shortest time. It was confirmed that the background fog disappeared after 2.5 minutes.

The paddle-shaped spiral developer conveying member 235C shown in FIG. 6 is provided with a paddle-shaped turbulent flow forming member 238 having an improved stirring performance as a conventional technique. It is difficult and expensive, and the paddle-shaped turbulence forming member has the highest stirring performance.
The saturated charge amount was reached in 25 minutes. 1 with the shortest background fog
Confirmed that there was no after a minute.

In the present invention, as shown in FIG. 3, a turbulent flow forming hole 239 is formed in the spiral blade 236 of the spiral developer conveying member 235 provided in the developer conveying path. The shape of the turbulent flow forming hole 239 is not limited to a circular shape as shown in the figure, and a good effect can be obtained with an oval, a polygon such as a square or a triangle. Along with the function of transporting the developer in the axial direction, the developer passes through the turbulent flow forming hole 239 of the spiral blade 236 to the side opposite to the blade 236 or is picked up by a bridge-like portion located above the turbulent flow forming hole 239. By this, turbulent stirring is positively performed.

As described above, new components for positively improving the stirring function are not required, and the cost can be improved without increasing the cost.

In the case where a hole was formed in the blade portion of the spiral developer conveying member of the present invention, the saturated charge amount was reached 1.6 minutes after the second shortest time. It was confirmed that the background fog was not 1.5 minutes.

Table 1 also shows the degree of toner scattering in the apparatus due to the difference in the shape of the spiral developer conveying member, together with the image background fog.

The toner used in the above experiment had a number average particle diameter of 6.5 μm according to the above-mentioned specification, but this number average particle diameter was changed to 2/5/8/11 μm. The recovery time of the charge amount was investigated by using the obtained material.

The time required for the toner to reach the saturation charge amount was measured for each toner number average particle diameter at a toner concentration of 4%. Table 2 also shows the relationship between the toner particle size and the fine line reproducibility.

[0065]

[Table 2]

The smaller the toner particle size, the longer the time required to reach the saturation charge. In other words, the smaller the diameter of the toner, the slower the rise in the amount of charge. This is because the ratio of the total surface area of the toner to the total surface area of the carrier is large, so the frequency of contact with the carrier surface required for the toner surface to reach the saturated surface charge density increases. I think to do.

It can be seen that the smaller the number-average toner particle size, the better the reproducibility of fine lines. Write at 400 dpi 8
The toner particle size capable of achieving a line / mm resolution (which can be recognized as a line) is 9 μm or less. Considering the variation of the image forming apparatus, the thickness is preferably 8 μm or less.

A toner particle size smaller than 2 μm is not preferable in terms of safety to the human respiratory system and prevention of toner scattering. In view of the fluctuation of the charge amount and the particle size distribution, the thickness is preferably 3.5 μm or more.

[0069]

According to the image forming apparatus of the present invention, a plurality of turbulent flow forming holes are formed in the spiral blade portion of the spiral developer transport member of the developing device to improve the toner transport performance and the stirring performance. Is now possible. Then, the recovery of the charge amount of the toner after a long stoppage is promptly performed, good image quality without fogging of the background portion can be obtained in a short time, and stable image formation can be efficiently performed. . In addition, dirt on the aircraft has been improved.

Further, after the image forming apparatus detects that the time during which the image forming apparatus has been stopped and left unattended becomes long, the spiral developer conveying member and the stirring wheel in the developing device are automatically rotated. The control and the standby at the time of starting the image formation can be performed efficiently.

Further, it was confirmed that the recovery time of the toner charge amount differs depending on the difference in the toner particle diameter. The smaller the particle diameter, the longer the recovery time but the better the resolution. However, it was confirmed that the number average particle size was 2 to 9 μm, and preferably 3.5 to 8 μm, in consideration of poor health if the diameter was reduced too much.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is a sectional view of a developing device used in the present invention.

FIG. 3 is a perspective view of a spiral developer conveying member used in the present invention.

FIG. 4 is a perspective view of a conventional spiral developer conveying member.

FIG. 5 is a perspective view of a conventional spiral developer conveying member.

FIG. 6 is a perspective view of a conventional spiral developer conveying member.

FIG. 7 is a graph showing a relationship between a time required for the toner to reach a saturated charge amount and a charge amount when only the spiral developer conveying member is rotationally driven.

FIG. 8 is a graph showing the relationship between the time required for the toner to reach a saturated charge amount and the charge amount when the developing device is driven at full rotation.

FIG. 9 is a control circuit diagram for operating a part of the developing device by detecting a long-term stoppage of the image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 21 Photoreceptor 23 Developing device 39, 54 Temperature detecting means 50 Fixing device 80 Control means 231 Main body case 232 Developing sleeve 234 Stirrer wheel 235, 235A, 235B, 235C Spiral developer conveying member 236 Spiral blade 239 Disturbance Flow forming hole

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 21/14 G03G 15/08 507L 21/00 372 (72) Inventor Toru Yamaguchi 2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares In-house F-term (reference) 2H005 AB06 EA05 FA02 2H027 DA11 DA12 EA04 EC06 ED08 EE01 EF06 2H077 AB02 AB14 AC02 AD06 AD13 AD23 AE03 AE06 DA18 DA20 DA82 DB25 EA03 GA03

Claims (6)

[Claims] An image forming apparatus comprising: a developing device that transports an electrostatic latent image formed on a photoconductor, which is an electrostatic latent image carrier, to a developing area by carrying a developer layer carried on a developing sleeve as a developer carrier; In the image forming apparatus having the developing device, the turbulent flow forming hole is provided in a part of the spiral blade of the spiral developer conveying member in the developing device so as to have a turbulent stirring function. An image forming apparatus comprising: 2. The developing device according to claim 1, wherein the electrostatic latent image formed on the photosensitive member as the electrostatic latent image carrier is transported to a developing area by carrying a developer layer carried on a developing sleeve as a developer carrier. In the image forming apparatus having the developing device, the developer is detected for a long time in the developing device, and when it is determined that the developing device has been left for a long time, the spiral developer conveying member in the developing device is used to recover the developer charge amount. And / or an image forming apparatus provided with control means for controlling the operation of the stirring member. 3. The method according to claim 2, wherein the determination of whether the developer has been left in the developing device for a long period of time is based on detection of a decrease in the temperature of the image forming apparatus or a decrease in the temperature of the fixing device of the image forming apparatus. The image forming apparatus as described in the above. 4. The image forming apparatus according to claim 1, wherein the developer used in the image forming apparatus is a two-component developer including a toner and a carrier. 5. The number average particle diameter of the toner is 2 to 9 μm.
The image forming apparatus according to claim 4, wherein 6. The image forming apparatus according to claim 4, wherein a part or all of the developer is manufactured by a polymerization method.