JP2007206288A - Image forming apparatus - Google Patents

Abstract

An image in which abnormal images can be eliminated by reliably detecting and correcting a difference in Vt due to linear velocity even when a deviation in Vt due to the linear velocity of a developer stirring member occurs due to the influence of aging or the environment. A forming apparatus is provided.
Image forming in which a developer stirring member having two or more linear velocities is driven at one linear velocity during process control, and toner density control is performed using an output value Vt of a magnetic permeability sensor during the process control. In the apparatus, when image formation is performed at a linear velocity different from that at the time of process control after process control, the difference between Vt at the time of image formation and Vt at the time of the process control is used as a Vt linear velocity correction amount, A value obtained by adding the Vt linear velocity correction amount to Vt at the time of image formation is defined as a corrected Vt.
[Selection] Figure 12

Description

  The present invention relates to an image forming apparatus that can eliminate abnormal images by reliably detecting and correcting a difference in Vt due to the linear velocity of a developer stirring member, and in particular, controls toner adhesion amount by a P sensor or the like during a job. The present invention relates to an image forming apparatus effective for those not to perform.

In recent full-color printers and copiers, the printing speed becomes slower to secure fixing energy when printing on thick paper and OHP sheets, and the printing speed becomes faster when printing black, which requires an increase in speed than full-color printing. Or As described above, one apparatus has two or more image forming speeds. Related documents include the following patent documents 1 and 2.
JP 2001-134066 A Japanese Patent Laid-Open No. 7-244428

  By the way, when the developer stirring speed is two or more linear speeds (linear speeds) as in the case of the image forming speed, especially when the speed is half or double the standard speed, the developer balance is lost and the developer drops. Since abnormalities such as unevenness in the left and right image densities (hereinafter referred to as ID) occur, the developer stirring speed is preferably one linear speed. However, in the conventional technology including the technology shown in the above-mentioned patent document, the developing device, the drive motor, and the gear are also miniaturized due to the downsizing and cost reduction of the device, so that the main body from the problem of layout and cost. Often changes at the same rate.

  Among them, a developing device that uses a magnetic permeability sensor (hereinafter referred to as a T sensor) in a two-component developing system and performs toner replenishment control has a T The flow of the developer is different, and the T sensor output value (hereinafter referred to as Vt) depending on the linear velocity is different. Therefore, the toner density (hereinafter referred to as TC) and the toner adhesion amount differ due to the switching of the linear speed, and abnormal quality such as low ID at high speed, excessive ID at low speed, and transfer dust may occur. is there.

  In order to eliminate the Vt linear velocity difference from a structural viewpoint, it has been found that the developer agitating member on the T sensor portion may be cut. However, when the developer fluidity is poor due to a high TC or a high number of sheet passing agents, the developer in the T sensor section is stagnated and erroneously detected, or the developer bulk density in the T sensor section during continuous white paper passing The state changes (bulk density decreases), but the TC is supposed to be constant, but the malfunction is that the TC is determined to be erroneously detected.

  Conversely, if a fin or mylar is attached as a part of the developer agitating member above the T sensor and the developer is always fluidized, the developer stays in the T sensor section or the developer bulk density state during continuous white paper feeding There is no change in the number, and false detection is eliminated, but the linear velocity difference becomes large. When the developer is fluidized by fins or the like, it is necessary to correct the Vt difference due to the linear velocity. The correction amount is normally constant at normal temperature and humidity, but initially it is almost constant, but if the developer fluidity is different due to aging, environment, etc., it will deviate. May cause abnormal quality.

  Therefore, the present invention has been made in consideration of the above-described circumstances, and even when a deviation in Vt due to the linear velocity of the developer stirring member occurs due to the influence of aging, environment, etc., the difference in Vt due to the linear velocity can be reliably ensured. It is an object of the present invention to provide an image forming apparatus capable of eliminating abnormal images by detecting and correcting.

  In order to solve the above problems, the invention according to claim 1 is a developer stirring member having two or more linear velocities in a process of forming an image using a two-component developer including a toner and a carrier. Is formed at a linear velocity different from that at the time of process control after the process control in the image forming apparatus that drives the toner density using the output value of the magnetic permeability sensor at the time of the process control. The magnetic permeability sensor at the time of image formation at the next different linear velocity is obtained by using the difference between the output value of the magnetic permeability sensor when performing the process and the output value of the magnetic permeability sensor at the time of the process control as a linear velocity correction amount. A value obtained by adding the linear velocity correction amount to the output value is used as the output value of the magnetic permeability sensor after correction.

  In the invention according to claim 2, in the image forming apparatus according to claim 1, when an image forming operation at a linear velocity different from the process control is performed immediately after the process control, the linear velocity is set before the image forming operation. A correction process is added.

  According to the present invention, the Vt difference in linear velocity (linear velocity difference) due to the influence of the developer state (age, environment) is detected by detecting and correcting the Vt difference due to the linear velocity (linear velocity) of the developer stirring member. Thus, it is possible to eliminate the occurrence of abnormal images such as low ID at high speed, excessive ID at low speed, transfer dust and the like that occur when the linear speed is switched. Due to the difference between Vt (stable toner density and developer balance in the developer) and Vt (toner density stable in the developer) operated at a different linear velocity immediately thereafter, the Vt line By determining the speed correction amount, it is possible to increase the accuracy of the Vt linear speed correction amount and eliminate the occurrence of abnormal images.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view of an image forming apparatus as the best mode for carrying out the present invention. 2 is an enlarged view of a broken line portion X (image forming portion) in FIG. 1 and 2, the image forming unit includes a photosensitive drum 2, a cleaning blade 8, a transfer belt 9, and a developing device 10. The photosensitive drum 2 is a cylindrical latent image carrier, and a cleaning blade 8 that removes transfer residual toner is provided at a position facing the photosensitive drum 2. Further, a transfer belt 9 for transferring an image formed on the photosensitive drum 2 to a transfer sheet is disposed below the photosensitive drum 2 so that the photosensitive drum 2 is in rolling contact with the transfer drum 9.

  A toner having a developing device 10 on the side of the photosensitive drum 2 and having a part exposed from the opening inside the developing casing of the developing device 10 having an opening formed toward the photosensitive drum 2. And a developing sleeve 1 made of a non-magnetic material as a developer carrying member for carrying a developer (two-component developer) made of a magnetic carrier on its surface, a magnet roller as a magnetic field generating means fixedly arranged inside the developing sleeve 1, A doctor 3 as a developer regulating member that regulates the amount of developer carried and conveyed on the developing sleeve 1, and a developer stirring member 7 that is located in the vicinity of the developing sleeve 1 and stirs the developer are provided. Yes. In this example, in order to perform full color printing with four color toners, four image forming units for forming toner images of the respective colors are arranged in a row.

  Here, a full color image forming operation will be described. In the image forming operation, the color separated image data is exposed and written on the surface of the photosensitive drum 1 to form an electrostatic latent image, which is visualized with colored toner corresponding to the color separated image data, and is formed on the conveying belt. Then, the toner image on the photosensitive drum 2 is sequentially transferred by the transfer belt 9 at each transfer position to the transfer paper conveyed to the respective image forming units to form a permanent full color image.

  The toner density in the developing device 10 is consumed by the image data, and is substantially supplied by replenishing the toner according to the image area and the value of the magnetic permeability sensor (hereinafter referred to as T sensor) C in the developing device 10. Kept constant. In addition, a plurality of halftone and solid patterns formed on the photosensitive drum 2 or the transfer belt 9 are processed once for 200 sheets (the number of sheets varies depending on the purpose and may be about 100 to 1000 sheets). The T sensor target value, the charging potential, and the light amount are set according to a mode in which the adhesion amount is converted by the P sensor and set so as to be the target adhesion amount. Unlike black-and-white monochrome machines, color printers and copiers have many opportunities to continuously form high-area images, so it is necessary to control with a high TC (high carrier coverage) as shown in the table of FIG. .

  Here, the shape of the developer stirring member 7 and the characteristics related to Vt will be described. FIG. 4 is a plan view of the developer stirring member 7, and FIG. 5 is a plan view showing fins and mylars (stirring portions at positions facing the T sensor C) on the developer stirring member 7. In FIG. 5, the fin width is indicated by A, the Mylar width is indicated by B, and the T sensor is indicated by C. FIG. 6 shows Vt-related characteristics when the Mylar width of the stirring member at a location facing the T sensor C is swung. FIG. 6 shows a case where the fin is fixed to 16 mm. The Vt-related characteristics mentioned here are: Vt linear velocity (linear velocity) shift amount when the Mylar width is changed (at the photosensitive member velocity of 125 to 185 mm / sec), T sensor sensitivity (V / wt%), This shows the amount of decrease in Vt (VcnT when the initial agent is 5 wt%).

The graph of FIG. 6 shows the following contents.
(1) Vt linear velocity shift amount: The Mylar width increases from 0.07 V to 0.64 V with a change from 0 to 5.5 mm (the Mylar width is narrow and the shift amount is reduced).
(2) T sensor sensitivity (V / wt%): Mylar width is changed from 1 mm to 5.5 mm, and is almost unchanged from 0.47 V to 0.50 V (not related to Mylar width).
(3) Vt drop amount during air stirring: Mylar width is reduced from 0.66V to 0.09V due to a change from 0 to 4 mm (mylar width is wide and reduction is reduced).
(4) Vcnt at initial agent: Mylar width increased from 5.9 V to 8.1 V with a change from 0 to 5.5 mm.
The same tendency was observed when the fin width was swung with the Mylar width fixed.

Thereby, the following results are obtained.
(A) By increasing developer mixing property in the vicinity of the T sensor (widening the fin / mylar width), the Vt linear velocity shift amount is increased / the Vt decrease amount during idle stirring is decreased.
(B) Due to a decrease in developer mixing property in the vicinity of the T sensor (narrowing the fin / mylar width), the Vt linear velocity shift amount is small / the Vt decrease amount during empty stirring is large.
(C) The above-mentioned a) and b) are trade-off relationships.
From these, it is understood that the Vt linear velocity difference (linear velocity difference) and the Vt decrease amount cannot be suppressed simultaneously under the mechanical conditions.

FIG. 7 is a characteristic diagram showing a change in Vt at the time of blank paper passing (without toner replenishment) when the T sensor portion has fins and Mylar is present (see FIG. 8) in the initial agent. FIG. 9 is a characteristic diagram showing a change in Vt at the time of passing a blank sheet (no toner replenishment) with a 50K sheet sheet developer with a T sensor portion with fins and a mylar (see FIG. 8). FIG. 10 is a characteristic diagram showing a change in Vt when a blank sheet is fed (no toner replenishment) when a 50K sheet developer is used and the T sensor portion is fin-cut and there is no mylar (see FIG. 11).
7, 9, and 10, the j part of Vt is at standard speed, the k part is at high speed, the l part is at low speed, and 200 sheets are passed through each part.

In the initial agent shown in FIG. 7, the Vt linear velocity difference is about 0.1 V (difference between j and k parts, difference between l and j parts), but it becomes larger in the case of the 50K sheet paper developer shown in FIG. ing. From this, it can be seen that the Vt linear velocity difference varies depending on the state of the developer, and it can be said that the Vt linear velocity correction amount cannot be a fixed value. In FIG. 10, the Vt linear velocity difference is eliminated even with the same 50K sheet passing developer, but the Vt decrease amount which is small in FIGS. 7 and 9 is large. Under mechanical conditions, it can be seen that if the Vt linear velocity difference is eliminated, a decrease in Vt occurs.
Since the Vt decrease amount differs depending on the amount of replenished toner, it cannot be corrected. However, the Vt linear velocity difference does not change as long as the developer fluidity is the same, so it is not necessary to correct frequently. Therefore, it can be said that the correction may be made when the environment is changed or when it is aged (long range such as 5K sheets, 10K sheets, etc.).

  Therefore, in this image forming apparatus, by detecting and correcting the Vt difference due to the linear velocity (linear velocity), the Vt linear velocity difference due to the influence of the developer state (environment and aging) is eliminated, and when the linear velocity is switched. It was made possible to eliminate the occurrence of abnormal images such as low ID (image density) at high speed, excessive ID at low speed, and transfer dust. FIG. 12 is a flowchart showing an operation example (first example) of the image forming apparatus. As shown in the figure, in the Vt linear velocity difference detection mode, a job start (data-in) is performed in step S10, and whether or not the development linear velocity is different from that in process control (hereinafter referred to as a process controller) in step S20. If there is a difference, the process proceeds to step S30, where it is confirmed whether or not the number of sheets passed after the process control is less than M sheets.

  In step S30, if the number is M or less, the process proceeds to step S40 to start an image forming operation, and the process proceeds to step S50 to start developing rotation and perform Vt reading. Then, the process proceeds to step S60, where the Vt linear velocity correction amount a is determined from the difference between the Vt at the time of the process control and the current sheet Vt. Vt is used. In step S20, if the developing linear speed is not different from that at the time of the process control, or if the number of sheets passed after the process control exceeds M sheets in step S30, the process proceeds to step S41 to start the image forming operation. In step S71, it is processed that there is no change in the linear velocity correction amount, and the image forming operation is terminated.

  Therefore, in this image forming apparatus, by detecting and correcting the Vt difference due to the linear velocity of the developer stirring member, the Vt linear velocity difference due to the influence of the developer state (age, environment) is eliminated, and the linear velocity switching is performed. It is possible to eliminate the occurrence of abnormal images such as low ID at high speed, excessive ID at low speed, and transfer dust. Due to the difference between Vt (stable toner density and developer balance in the developer) and Vt (toner density stable in the developer) operated at a different linear velocity immediately thereafter, the Vt line By determining the speed correction amount, it is possible to increase the accuracy of the Vt linear speed correction amount and eliminate the occurrence of abnormal images.

  FIG. 13 is a flowchart showing an operation example (second example) of the image forming apparatus. As shown in the figure, in the Vt linear velocity difference detection mode, a job start (data in) is performed in step S11, and whether or not the development linear velocity is different from that in process control (hereinafter referred to as a process controller) in step S12. If there is a difference, the process proceeds to step S13, where it is confirmed whether or not the number of sheets after the process control is less than M sheets.

  In step S13, if the number is M or less, the process proceeds to step S14, where the developer is idled for N seconds at the linear speed at the time of image formation, and the developer balance is made uniform. For N seconds, it is desirable that the developer in the developing unit is one turn or more. Thereafter, Vt is read in step S15, and the process proceeds to step S16, where the Vt linear velocity correction amount a is determined from the difference between the Vt at the time of the process control and the Vt at the time when the current linear velocity is idle for N seconds. In steps S17 and S18, Vt + a Vt is used during image formation. If it is determined in step S12 that the development linear speed is not different from that in the process control, or if the number of sheets passed after the process control exceeds M sheets in step S13, the process proceeds to step S19, where the linear speed correction amount is not changed. Thereafter, the image forming operation is started in step S21, and then the image forming operation is ended.

  In this way, by adding a short stirring mode before passing another line speed, the developer balance at the other line speed can be stabilized, and the amount of line speed can be detected at a stable Vt. Can do. Furthermore, the accuracy of the Vt linear velocity correction amount can be increased and the occurrence of abnormal images can be eliminated.

The developing conditions of the image forming apparatus are shown below.
Mechanical conditions:
Gap between the developing sleeve and the photosensitive drum (hereinafter referred to as GP) 0.4 to 0.6 mm
Gap between the developing sleeve and doctor blade (hereinafter referred to as GD) 0.4 to 0.6 mm
Development sleeve diameter 18φ
Photoconductor linear speed 60-250mm / sec
Ratio of developing roller linear velocity to photosensitive member linear velocity 1.1 to 1.8

Developer:
Carrier ferrite average 50-70 μm
Toner polyol resin, polyester resin average particle size 6-7 μm
Additive amount 0.5-2.0wt%
Carrier coverage 30-80%
Charge amount (Q / M) 10-30 μC / g

1 is a schematic sectional view of an image forming apparatus as the best mode for carrying out the present invention. FIG. 2 is an enlarged view of a broken line part X (image forming part) in FIG. 1. It is a figure which shows the table | surface which put together the carrier coverage of a full color printer and a monochrome printer. 3 is a plan view of a developer stirring member 7. FIG. 6 is a plan view showing fins and mylars on the developer stirring member 7. FIG. It is a graph which shows the Vt related characteristic when the Mylar width | variety of the stirring member of the location facing T sensor C is shaken. It is a graph which shows Vt transition at the time of a white paper passing with a T sensor part with a fin and a mylar in an initial agent. FIG. 8 is a plan view of the developer stirring member in the state of FIG. 7. FIG. 10 is a graph showing the transition of Vt when a blank sheet is fed with a T sensor unit having fins and a mylar with 50K sheet developer. FIG. 10 is a graph showing a change in Vt when a T-sheet sensor is fin-cut with 50K sheets of sheet developer and a blank sheet is passed without a mylar. FIG. 11 is a plan view of the developer stirring member in the state of FIG. 10. 3 is a flowchart illustrating an operation example (first example) of the image forming apparatus. 5 is a flowchart illustrating an operation example (second example) of the image forming apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Developing sleeve, 2 Photosensitive drum, 3 Doctor, 7 Developer stirring member, 8 Cleaning blade, 9 Transfer belt, 10 Developing apparatus

Claims (2)

In the process of forming an image using a two-component developer including a toner and a carrier, a developer stirring member having two or more linear velocities is driven at one linear velocity during process control, and the transparency during the process control is driven. In an image forming apparatus that controls toner density using an output value of a magnetic sensor,
The difference between the output value of the magnetic permeability sensor when image formation is performed at a linear velocity different from that at the time of process control after the process control and the output value of the magnetic permeability sensor at the time of the process control are used as a linear velocity correction amount next time. An image forming apparatus characterized in that a value obtained by adding the linear velocity correction amount to the output value of the magnetic permeability sensor at the time of image formation at another linear velocity is used as the corrected output value of the magnetic permeability sensor. The image forming apparatus according to claim 1.
An image forming apparatus, wherein an image forming operation at a linear velocity different from that of the process control is performed immediately after the process control, and a linear velocity correction process is added before the image forming operation.

Images