JP4578905B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a printer, a copying machine, and a FAX. More specifically, the toner concentration of a developing device using a two-component developer including toner and a carrier is controlled by a magnetic permeability sensor. The present invention relates to an image forming apparatus including a developing device having a developing stirring member speed of 2 linear speeds or more.

In modern full-color printers and copiers, when printing on cardboard and OHP sheets, the image forming speed is slow to ensure fixing energy and the writing processing speed, and when printing black, it is required to increase the speed compared to full color. There are machines that have two or more image forming speeds with one machine.
As with the image forming speed, when the developing agitation speed is at least 2 linear speeds, especially half speed or double speed relative to the standard speed, the developer balance is lost, the developer falls, and the left and right image density (hereinafter referred to as “ID”). The development stirring speed is preferably 1 linear speed.
However, along with the downsizing and cost reduction of the machine, the developing device, the drive motor, and the gears are also downsized, and the speed often changes at the same rate as the main body due to layout and cost problems.
Among the two-component developing systems, a developing device that performs toner replenishment control using a magnetic permeability sensor (hereinafter referred to as “T sensor”) has two or more developing agitation speeds and the agent on the T sensor unit. The T sensor output value (hereinafter referred to as “Vt”) due to the linear velocity is different.
For this reason, 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.

It has been found that the development stirring member on the T sensor portion may be cut to mechanically eliminate the Vt linear velocity difference. However, when the developer has poor fluidity due to a high TC, a high number of paper passing agents, etc., the developer in the T sensor unit is stagnated and erroneously detected. In some cases, the density state changes (the bulk density decreases), and there is a problem of erroneous detection that the TC is determined to be high despite the TC being constant.
Conversely, if fins or mylars are attached to the developer stirring member on the T sensor unit and the developer is constantly fluidized, the developer retention in the T sensor unit or the change in the developer bulk density state during continuous white paper feeding There is no false detection, 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 amount of correction is normally constant at normal temperature and humidity, but it may shift if the developer fluidity changes over time or in the environment. Abnormal quality may occur.

In Patent Document 1, a developer carrier that carries a two-component developer by controlling a rotation speed and an applied voltage even under conditions in which so-called carrier development is likely to occur, and a developer carrying member that has a surface potential controlled, And an image forming apparatus including a photoconductor that forms a toner image with toner supplied from the photoconductor. At least one of the rotation speed of the developer carrier, a DC component of the applied voltage, and the surface potential of the photoconductor. By changing one of them, a good image is output.
Further, in Patent Document 2, in order to eliminate variations in the initial printing density after the blended developer is charged, the developer blended with a constant toner density is charged into the developing device and the initial printing is started. Then, the reference level of the comparison circuit is changed to be higher than the reference level at the time of adding the prepared developer, the toner 1 is replenished to the prepared developer, and the developing device until the relationship between the detection level of the toner density sensor and the reference level is satisfied. Mixing adjustment is performed, and stable print quality is obtained even in initial printing.
JP 2001-134066 A Japanese Patent Laid-Open No. 7-244428

However, even in the above example, in the developing device using the magnetic permeability sensor, when the time or environment changes, and the magnetic sensor output is shifted due to the linear speed of the developing stirring speed, the balance of the developer is There is a problem that abnormalities such as collapse, developer dropping, and unevenness of the left and right IDs occur.
The present invention has been made in view of the above problems, and even when a deviation occurs in the magnetic permeability sensor output due to linear velocity over time or in the environment, the abnormal image can be reliably detected and corrected. In particular, the present invention provides a developing device and an image forming apparatus provided with the developing device that are particularly effective for a device that does not perform toner adhesion amount control by a P sensor or the like during a job.

In order to achieve the above object, the present invention controls the toner concentration of a developing device using a two-component developer including toner and carrier by a magnetic permeability sensor, and the developing stirring member speed is a developing speed of 2 linear speeds or more. Oite an image forming apparatus including the apparatus, the developing device detects the magnetic permeability sensor output value difference by linear velocity, the magnetic permeability sensor output value difference linear velocity correction amount from the magnetic permeability sensor output value when the linear velocity switching A developing device that determines the reference magnetic permeability sensor output value based on the magnetic permeability sensor output value when performing process control at one linear speed, and at the time of image formation of the linear speed at the time of process control and the previous job when the linear velocity of the different image type, characterized by determining the permeability sensor output value difference linear speed correction amount by the difference between the magnetic permeability sensor output and the reference permeability sensor output at the time of image formation of the job Apparatus Ru Der.

The present invention further when switching the linear velocity, an image forming apparatus and determines the permeability sensor output value difference linear velocity correction amount during the preliminary rotation during the fixing temperature adjustment.
The invention further image formation, wherein when switching to the low linear velocity, determines the permeability sensor output value difference linear velocity correction amount during the preliminary rotation during fixing temperature adjustment that after a lapse printed over a certain number of Device.

According to the present invention, by detecting and correcting the difference in output value of the magnetic permeability sensor due to the linear velocity, it is possible to eliminate the Vt linear velocity difference due to the influence of the developer state (aging, environment), and the high speed generated when the linear velocity is switched. It is possible to eliminate abnormal quality such as low ID at time, excessive ID at low speed, and transfer dust.
Also, by determining the Vt linear velocity correction amount at Vt during normal operation, it is possible to create a mode that requires a special time and eliminate abnormal quality without reducing productivity.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The following description is an example of the best mode of the present invention, and it is easy for those skilled in the art to make other embodiments within the scope of the claims by making changes and modifications within the scope of the claims. However, this does not limit the scope of the claims.

FIG. 1 is a schematic view of a developing device of an image forming apparatus according to the present invention. FIG. 2 is a schematic diagram showing an enlarged broken-line circle X in FIG.
1 and 2, this developing device is disposed on the side of a cylindrical photosensitive drum 2 which is a latent image carrier used in a printer or a copying machine, and an opening (see FIG. 2) is directed toward the photosensitive drum 2. A developing sleeve 1 is arranged inside a developing casing in which a not-shown) is formed.
A developing sleeve 1 made of a non-magnetic material as a developer carrying member carrying a developer made of toner and a magnetic carrier partially exposed from the opening is fixedly disposed inside the developing sleeve 1. As a magnetic field generating means, a magnet roller and a doctor 3 as a developer regulating member for regulating the amount of the developer carried on the developing sleeve 1 are provided.
A full-color image forming operation will be described. There are writing that exposes the color-separated image data around the photosensitive drum 2 that is the image carrier itself, a developing device that has colored toner corresponding to the color-separated image data, and a cleaning device that removes the transfer residual toner. The four image forming units thus arranged are arranged in a line.
The transfer paper conveyed to the respective image forming portions by the transfer belt 4 sequentially receives the transfer of the toner image on the photosensitive drum 2 by the transfer means 5 at each transfer position, and the transfer means 5 makes permanent full color. An image is formed.

The toner density in the developing device is kept almost constant by replenishing toner according to the amount of toner consumed by the image data, the image area, and the value of the permeability sensor (hereinafter referred to as T sensor) 6 in the developing device. It is.
In addition, a process control (a plurality of halftones and solid patterns formed on the photosensitive drum 2 or the transfer belt 4) is performed once per 200 sheets (the number of sheets varies depending on the target, even about 100 to 1000 sheets) by a P sensor. 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 and set so as to achieve the target adhesion amount.

FIG. 3 is a relationship diagram showing the carrier coverage of the full-color printer and the monochrome printer. Unlike color monochrome printers and color printers, color printers and copiers have many opportunities to continuously form high-area images, and therefore need to be controlled with high TC (high carrier coverage).
FIG. 4 is a schematic diagram showing the relationship between the T sensor unit stirring member and the T sensor. Here, the shape of the T-sensor stirring member 7 and the characteristics related to Vt will be described. The fin width is part A, and the mylar width is part B. T sensor is C.

FIG. 5 is a characteristic diagram showing Vt-related characteristics when the mylar width of the T sensor unit stirring member 7 is changed. The fin is fixed at 16 mm. The Vt-related characteristics here are the Vt linear velocity shift amount when the mylar width is changed (at the photosensitive member speed of 125 to 185 mm / sec), the T sensor sensitivity (V / wt%), the Vt decrease amount at the time of idle stirring, Vcnt) when the initial agent is 5 wt%.
1) Vt linear velocity shift amount (125-185): Mylar width 0 → 5.5mm, 0.07 → 0.64V up (mylar width narrower, shift amount reduction)
2) T sensor sensitivity (V / wt%): Mylar width 1 → 5.5mm, 0.47 → 0.50V, no change (not related to Mylar width)
3) Vt drop amount during empty stirring: Mylar width 0 → 4mm, 0.66 → 0.09V down (Mylar width is wide, reduction amount is reduced)
4) (Vcnt at the time of initial agent): Mylar width 0 → 5.5 mm and up to 5.9 → 8.1 V The same tendency was observed when the mylar width was fixed and the fin width was changed. This gives the following results:
a. When the developer mixing property near the T sensor is increased (fin / mylar width is increased), the Vt linear velocity shift amount is increased / the Vt decrease amount during idling is decreased.
b. When the developer mixing property near the T sensor is reduced (fin / mylar width is narrowed), the Vt linear velocity shift amount becomes large / the Vt decrease amount becomes large during idle stirring.
c. ab is a trade-off relationship.
From these, it is understood that the Vt linear velocity difference and the Vt decrease amount cannot be suppressed simultaneously under the mechanical conditions.

FIG. 6 is a characteristic diagram showing a change in Vt when a blank sheet is passed (without toner replenishment) with T sensor portion fin + mylar in the initial agent. FIG. 7 is a characteristic diagram showing a change in Vt at the time of passing a blank sheet (no toner replenishment) with a T sensor portion fin + mylar with 50k sheets passing agent. FIG. 8 is a characteristic diagram showing a change in Vt when a blank sheet is fed (no toner replenishment) with T sensor portion fin cut + no mylar with 50k sheets passing agent.
6 to 8, the blue part (j) of Vt is at the standard speed, the black part (k) is at high speed, and the red part (l) is at low speed. 200 sheets each. FIG. 6 shows T sensor portion with fin + mylar, initial developer, FIG. 7 shows T sensor portion with fin + mylar, 50k sheet developer, and FIG. 8 shows T sensor portion fin cut + no mylar, 50k sheet. Paper developer.
Schematic diagrams of the T sensor unit agitating member and the T sensor are shown in FIG. 6 with T sensor unit fins + mylar and FIG. 7 with T sensor units fin cut + no mylar.

In the initial agent of FIG. 6, the Vt linear velocity difference is about 0.1 V (the difference between the blue part (j) and the black part (k), the difference between the red part (l) and the blue part (j)). It becomes large at the time of 50k run. From this, it can be seen that the Vt linear velocity difference varies depending on the developer state, and it can be said that the Vt linear velocity correction amount cannot be a fixed value.
In FIG. 8, the Vt linear velocity difference is eliminated even with the same 50k sheet passing agent, but the Vt decrease amount which is small in FIGS. 6 and 7 is large. It can be seen that when the Vt linear velocity difference is eliminated mechanically, a decrease in Vt occurs.
The Vt drop amount cannot be corrected because it varies depending on the amount of replenished toner, but the Vt linear velocity difference does not change as long as the developer fluidity is the same, and therefore does not need to be corrected frequently. It can be said that the correction may be made when the environment changes or over time (long range such as 5K sheets, 10K sheets, etc.).

FIG. 9 is a flowchart for explaining the Vt linear velocity difference detection mode.
FIG. 9 shows the process control Vt during process control when the process control (procedure) start (A10) and Vt reading (A20) are different (A30) when the linear velocity is different between the process control and the previous image formation. And the difference a between the previous image formation Vt (A40) and the linear velocity correction amount is changed or updated to obtain the linear velocity correction amount. The linear velocity correction amount is effective when this process control is interrupted at the end of image formation or during image formation.
As described above, by detecting and correcting the Vt due to the linear velocity, it is possible to eliminate the Vt linear velocity difference due to the influence of the developer state (time, environment). Abnormal quality such as excessive ID and transfer dust can be eliminated.
Also, by determining the Vt linear velocity correction amount from Vt during normal operation and Vt during process control, it is possible to create a mode that requires a special time and eliminate abnormal quality without reducing productivity.
Figure 10 is a Ru flowchart der illustrating another Vt linear velocity difference detection mode.
In FIG. 10, job start (B10), the fixing device starts preliminary (pre) rotation (B20). At that time, when the linear velocity is different from that at the previous image formation (B30) and B or more (for example, 5K or 10K) from the previous Vt linear velocity correction (for example, 5K or 10K) (B40), development rotation is started and Vt is read. (B50). At that time, PCU rotation, charging, and development bias are also applied so that an abnormal image (carrier adhesion or solid image) does not occur. The difference a between the Vt of the previous job and the Vt of the current pre-rotation is calculated (B60), and the linear velocity correction amount is changed (updated) to become the linear velocity correction amount.

As described above, by detecting and correcting the Vt due to the linear velocity, it is possible to eliminate the Vt linear velocity difference due to the influence of the developer state (time, environment). Abnormal quality such as excessive ID and transfer dust can be eliminated.
Also, by determining the Vt linear velocity correction amount from Vt during normal operation and Vt during fixing temperature adjustment pre-rotation, a mode that requires special time is created, and abnormal quality is eliminated without reducing productivity. Can do.
Further, by adjusting the fixing temperature at the time of linear speed switching and developing agitation during pre-rotation and reading Vt, the Vt linear speed correction amount can be determined in a state where the developer Vt just before image formation at the time of linear speed switching is not affected by toner replenishment. Can do. The accuracy of the Vt linear velocity correction amount can be increased and abnormal quality can be eliminated.
In addition, it is possible to eliminate the influence of developer deterioration due to idle rotation, to increase the accuracy of the Vt linear velocity correction amount, and to eliminate abnormal quality.

The development conditions of the present invention are shown below.
Mechanical conditions Gap between developing sleeve and photosensitive drum (hereinafter referred to as GP) 0.4 to 0.6 mm
Gap between development 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 1.1-1.8
Developer Carrier: Ferrite (average 50-70 μm)
Toner: Polyol resin, polyester resin (average particle size 6-7 μm, additive amount 0.5-2.0 wt%, carrier coverage 30-80%, charge amount (Q / M) 10-30 μC / g)
By determining the Vt linear velocity correction amount when there is no influence of toner replenishment, the accuracy of the Vt linear velocity correction amount can be increased and abnormal quality can be eliminated. It is possible to eliminate the influence of the deterioration of the developer, increase the accuracy of the Vt linear velocity correction amount, and eliminate the abnormal quality.

1 is a schematic view of a developing device of an image forming apparatus according to the present invention. It is the schematic which expands and shows the broken-line circle | round | yen X of FIG. It is a relationship figure which shows the carrier coverage of a full color printer and a monochrome printer. It is the schematic which shows the relationship between a T sensor part stirring member and T sensor. It is a characteristic view which shows the Vt related characteristic when changing the mylar width | variety of the T sensor part stirring member 7. FIG. FIG. 6 is a characteristic diagram showing a change in Vt when a blank sheet is passed (with no toner supply) when the initial agent has T sensor portion fins + mylars. FIG. 10 is a characteristic diagram showing a change in Vt when a blank sheet is fed (no toner replenishment) with a Tk sensor portion with fins + mylar with 50k sheets passing agent. FIG. 10 is a characteristic diagram showing a change in Vt when a blank sheet is fed (no toner replenishment) with T sensor portion fin cut + mylar without 50k sheet passing agent. It is a flowchart explaining Vt linear velocity difference detection mode. It is a flowchart explaining Vt linear velocity difference detection mode.

Explanation of symbols

1 Developing device (Developing sleeve)
2 Photoconductor 3 Doctor blade 4 Transfer belt 5 Transfer means 6 Magnetic permeability sensor 7 Stirring member 8 Cleaning blade 9 Exposure 10 Fixing device

Claims (3)

Control the toner density of a developing device using a two-component developer containing toner and carrier by a magnetic permeability sensor,
Oite an image forming apparatus including a developing device developing agitating member speed has two or more wire speed,
The developing device includes:
A developing device that detects a permeability sensor output value difference based on a linear speed and determines a magnetic sensor output value difference linear speed correction amount from the permeability sensor output value when the linear speed is switched ,
The reference permeability sensor output value is determined by the permeability sensor output value when process control is performed at one linear velocity.
When the linear velocity at the time of process control and the linear velocity at the time of image formation of the previous job are different, the magnetic sensor output value is the difference between the magnetic permeability sensor output at the time of image formation of the job and the reference magnetic permeability sensor output. An image forming apparatus characterized by determining a difference linear velocity correction amount. The image forming apparatus according to claim 1.
An image forming apparatus characterized in that, when the linear velocity is switched, a magnetic sensor output value difference linear velocity correction amount is determined during preliminary rotation at the time of fixing temperature adjustment . The image forming apparatus according to claim 1 , wherein
An image forming apparatus characterized by determining a magnetic sensor output value difference linear velocity correction amount at the time of preliminary rotation at the time of fixing temperature adjustment when switching to a low linear velocity after a predetermined number of sheets have been printed .

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