JP2005172868A - Developing device and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device in which image defects can be prevented by ensuring detection and correction even in the event that a Vt varies with a linear velocity due to aging, environment, etc., and which is effective in, in particular, the type that does not include the controlling of an amount of attached toner by a P sensor or the like during a job, and to provide an image forming apparatus that has the developing device. <P>SOLUTION: Using a magnetic permeability sensor 6, the developing device controls toner concentration in the developing device 1 that uses two-component developer containing toner and carrier. The developing device has two or more linear velocities of a developer stirring member 7. In the developing device, a difference in magnetic permeability sensor output value is detected by the linear velocities. An amount of correction of the linear velocity, which matches the difference in the magnetic permeability sensor output value, is determined based upon the difference in the magnetic permeability sensor output value obtained when the linear velocity is switched. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device used for an electrostatic copying apparatus, a printer, a facsimile, and the like and an image forming apparatus provided with the developing device.

In recent full-color printers and copiers, the printing speed is slower for securing fixing energy and writing processing speed when printing on cardboard and OHP sheets, and higher speed is required for black printing because it is required to be faster than full-color printing. There are machines that have two or more image forming speeds in one machine. Related documents include the following patent documents 1 and 2.
JP 2001-134066 A Japanese Patent Laid-Open No. 7-244428

In the above prior art, when the developing agitation speed is two or more 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, the developer drops, the left and right ID unevenness, etc. Therefore, it is desirable that the development stirring speed be 1 linear speed.
However, as the machine becomes smaller and the cost is reduced, the developing device, the drive motor, and the gear are also made smaller, and the speed is often changed at the same rate as the main body due to layout and cost problems.
Among the two-component developing methods, a developing device that performs toner replenishment control using a magnetic permeability sensor (hereinafter referred to as a T sensor) causes the developer flow on the T sensor portion to flow at two or more developing agitation speeds. In contrast, the T sensor output value (hereinafter referred to as Vt) varies depending on the linear velocity.
For this reason, the toner density (hereinafter referred to as TC) and the toner adhesion amount differ depending on 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 in order to eliminate the Vt linear velocity difference mechanically, the developer stirring member on the T sensor unit may be cut. However, when the developer has poor fluidity due to a high TC or a high number of sheet passing agents, the developer in the T sensor unit is retained and erroneously detected. There is a problem that the TC is supposed to be constant but erroneously detected because the TC is constant (the bulk density decreases).
On the other hand, if the developer stirring member on the T sensor part is attached with fins or mylar and the developer is always fluidized, the developer stays in the T sensor part or changes 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 initially it will shift if the developer fluidity differs due to aging or the environment. May occur.
Accordingly, an object of the present invention is to eliminate abnormal images in order to reliably detect and correct even when a deviation occurs in Vt due to linear velocity over time or in the environment in order to solve the above-described problems. In particular, it is an object of the present invention to provide 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 solve the above-mentioned problems, in the invention described in claim 1, the toner concentration of the developing device using the two-component developer containing toner and carrier is controlled by the magnetic permeability sensor, and the developer stirring member speed is 2 In a developing device having a linear speed or higher, a magnetic sensor output value difference is detected based on the linear velocity, and a magnetic sensor output value difference linear velocity correction amount is determined from the magnetic sensor output value difference when the linear velocity is switched. It is characterized by.
According to a second aspect of the present invention, the developing device according to the first aspect is characterized in that the magnetic permeability sensor output value difference linear velocity correction amount is determined when there is no toner replenishment during image formation.
According to a third aspect of the present invention, the magnetic permeability sensor output value difference linear velocity correction amount is an average of a certain number of recent permeability sensor output value difference linear velocity correction amounts. Features the device.
According to a fourth aspect of the present invention, there is provided an image forming apparatus including the developing device according to any one of the first to third aspects.

According to the present invention, by detecting and correcting a T sensor output value difference (hereinafter referred to as Vt) due to a linear velocity, it is possible to eliminate the Vt linear velocity difference due to the influence of the developer state (time, environment). It is possible to eliminate abnormal qualities such as low ID at high speed, excessive ID at low speed, transfer dust and the like that occur at the time of fast switching.
Also, by determining the Vt linear velocity correction amount at Vt during normal operation, abnormal quality can be eliminated without creating a mode that requires a special time and reducing productivity.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of a developing device related to 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 has an opening (see FIG. 1). A developing sleeve 1 is arranged inside a developing casing (not shown) 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 units 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 the toner according to the amount of toner consumed by the image data, the image area, and the value of the magnetic permeability sensor (hereinafter referred to as T sensor) 6 in the developing device. It is.
Also, process control (a plurality of halftones and solid patterns formed on the photosensitive drum 2 or the transfer belt 4 are attached by the P sensor once per 200 sheets (the number of sheets varies depending on the target, even 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 amount is converted and set so that the target adhesion amount is obtained.

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. Reference numeral 6 denotes a T sensor.
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): Increased from 5.9 to 8.1 V with a Mylar width of 0 → 5.5 mm.
The same tendency was observed when the fin width was swung with the mylar width fixed. 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 is small / the Vt decrease amount is 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 at the time of passing a blank sheet (without toner replenishment) with T sensor portion finned + mylar in the initial agent. FIG. 7 is a characteristic diagram showing a change in Vt when a 50k sheet T sensor portion has fins + mylars and a blank sheet is passed (no toner replenishment). FIG. 8 is a characteristic diagram showing a change in Vt when T paper is fed with no T sensor portion fin cut + mylar (no toner replenishment).
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. 6 shows T sensor portion with fin + mylar, initial developer, FIG. 7 shows T sensor portion with fin + mylar, 50K sheet developer, 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.
In the initial developer shown in 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)). The 50K run is bigger. From this, it can be seen that the Vt linear velocity difference differs 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. 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 under mechanical conditions, a Vt decrease amount 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 is switched or over time (long range such as 5K sheets, 10K sheets).

FIG. 9 is a flowchart for explaining the Vt linear velocity difference detection mode. Job start (S1), image forming operation starts (S2), and Vt is read (S3). At that time, it is determined whether or not the replenishment time is Smsec or less (0 msec is high in accuracy) (S4), and if it is Smsec or less, it is determined whether or not the linear velocity is different from the previous image formation (S5).
When the line speed is different, the line speed is corrected. The difference m between Vt at the time of the previous image formation and the current Vt (S3) is calculated (S6), and the average is calculated with this m and the cumulative average n so far (for example, the past 10 times), and the linear velocity correction amount is calculated. Determine (S7), change (update) (S8), and terminate the image forming operation.
If the linear velocity does not differ in (S5), the image forming operation is terminated as no change in the A linear velocity correction amount (S9). When calculated in the past 10 times, (m + n × 10) / (1 + 10) = A: linear velocity correction amount.

The development conditions of the present invention 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 development sleeve and doctor blade (hereinafter referred to as GD) 0.4 to 0.6 mm
Development sleeve diameter 18φ
Photoconductor drum linear speed 60-250mm / sec
Ratio of developing roller linear velocity to photosensitive drum 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 related to an image forming apparatus according to the present invention. It is the schematic which expands and shows the 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 the mylar width | variety of T sensor part stirring member 7 is shaken. FIG. 10 is a characteristic diagram showing a change in Vt when a T sensor portion has fins + mylars and blank paper is passed (no toner replenishment). FIG. 10 is a characteristic diagram showing a change in Vt when a T sensor portion has fins + mylars and blank paper is passed (no toner replenishment). FIG. 10 is a characteristic diagram showing a change in Vt when T paper is fed with no T sensor portion fin cut + mylar (no toner replenishment). It is a flowchart explaining Vt linear velocity difference detection mode.

Explanation of symbols

1 Developing device (Developing sleeve)
6 Magnetic permeability sensor (T sensor)
7 Stirring member Vt T sensor output value difference

Claims (4)

  In a developing device in which the toner density of a developing device using a two-component developer containing toner and carrier is controlled by a magnetic permeability sensor, and the developer stirring member speed is at least two linear speeds, the output value of the magnetic permeability sensor by the linear speed A developing device that detects a difference and determines a magnetic sensor output value difference linear speed correction amount from a magnetic sensor output value difference when the linear speed is switched.   The developing device according to claim 1, wherein the magnetic permeability sensor output value difference linear velocity correction amount is determined when there is no toner supply at the time of image formation.   3. The developing device according to claim 1, wherein the magnetic permeability sensor output value difference linear velocity correction amount is an average of a certain number of recent magnetic permeability sensor output value difference linear velocity correction amounts. An image forming apparatus comprising the developing device according to claim 1.

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