JP2007121855A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which is capable of performing TC measurement of high precision by suppressing measurement errors among sensors and devices to extremely reduce an influence of deterioration with time of toner, and a process cartridge and an image forming apparatus having the developing device. <P>SOLUTION: A developing device 8 in an electrophotographic system using a two-component developer has a permeability sensor 3 for measuring a toner density and uses two or more different kinds of toner densites to adjust the permeability sensor 3 when starting to use the developing device 8, and the process cartridge and the image forming apparatus include the developing device 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device having a magnetic permeability sensor for measuring toner density in a two-component electrophotographic copying machine or printer. Furthermore, the present invention relates to a process cartridge having the developing device and an image forming apparatus.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, an electrostatic latent image corresponding to image information on a latent image carrier (hereinafter referred to as a photosensitive member) such as a photosensitive drum or a photosensitive belt. An image is formed, and a visible image is obtained by a developing operation performed by a developing device having a developer carrier (hereinafter referred to as a developing roller). As such a developing means, a two-component developing system including a toner and a carrier is widely used from the viewpoint of transferability, halftone reproducibility, temperature / humidity stability, and the like.
Here, as an important characteristic value of the two-component development method, there is a toner density (hereinafter referred to as TC) in the developing machine. TC has a great influence on image quality such as density and color tone, and also causes problems such as toner scattering and background contamination at high TC, and carrier adhesion at low TC. Therefore, it is required that the TC in the developing device can be detected with high accuracy, and in many image forming apparatuses, a magnetic permeability sensor is used. Also, the sensor output is adjusted using a known TC developer set in the developing device at the start of use of the developing device.

Therefore, in Patent Document 1, a two-component developer composed of a carrier and toner is held in a developing device of an image forming apparatus, and the permeability of the held developer is detected by a permeability sensor, and the permeability is changed. A toner density control method is disclosed in which a means for controlling the toner density in the developing device functions according to the detection output of the sensor. The relationship between the change in the toner density of the developer and the change in magnetic permeability is checked in advance to determine whether toner density control is possible by detecting the toner density with a magnetic permeability sensor. When it is confirmed that the output of the magnetic permeability sensor changes in the direction in which the magnetic permeability decreases when the developer is stirred, the toner concentration can be controlled by the detection value of the magnetic permeability sensor. As a result, the charging characteristics of the developer change greatly and the bulk density of the developer also changes, so that toner density control does not run away in a state where the relationship between increase / decrease in toner density and decrease / increase in magnetic permeability is broken. It is possible to provide a control method that can be performed.

Further, in Patent Document 2, the toner concentration of a two-component developer composed of toner and a magnetic carrier and filled in a developing device is detected by the output of a magnetic permeability sensor, and the output exceeds a certain level. In a toner concentration control method in which toner is replenished into the developing device from a replenishing toner storage container attached to the developing device, the toner is calculated based on the sensor output value and the sensor output increase rate (ΔV / ΔT). It is disclosed that after replenishment and after toner replenishment, only the developer agitation operation is performed for a certain period of time without performing the image forming cycle in accordance with the output increase rate. As a result, there is a problem such as a decrease in toner density that occurs when a large amount of toner is consumed due to an image output with a high image ratio, a decrease in image density, carrier skip, image unevenness due to toner density unevenness, and erroneous detection of toner empty. Can be effectively avoided.

Furthermore, in Patent Document 3, a toner replenishment amount is determined from a relationship between a predetermined detection voltage value and a toner replenishment amount and a detection voltage value when the toner end is actually detected, and a desired developer toner concentration is obtained. Thus, a method for canceling toner end detection by replenishing toner is disclosed. As a result, it is possible to obtain a stable image density by suppressing excessive toner replenishment before and after releasing the toner end.

Further, in Patent Document 4, the control unit stirs the developer with the stirring unit at a stirring speed corresponding to a plurality of different image formation speeds, and the detection levels detected by the detection unit at the respective stirring speeds are the same level. It is disclosed that the toner replenishment amount of the toner replenishing means is adjusted so as to be. This makes it possible to supply toner stably even in processes with different stirring speeds.

JP 2002-333767 A JP 2004-317960 A JP 2002-269891 A Japanese Patent Laid-Open No. 2004-53744

However, even if the means described in Patent Document 1 is used, the permeability type sensor has a large variation in sensitivity among individuals, and even if adjustment is performed, the TC measurement error between the sensors increases as the distance from the TC at the time of adjustment increases. There was a problem of becoming larger.
Further, even if the means described in Patent Document 2 is used, there is a problem that the influence of toner deterioration due to use cannot be avoided, and the TC measurement error increases with time.
Further, although the influence of the toner over time can be reduced by the method described in Patent Document 3, a highly accurate TC is still required due to the influence of the external environment such as temperature and humidity and the influence of the toner lot blur. Measurement could not be performed, which was a problem.
In addition, the method of Patent Document 4 can mitigate the influence of the process, but it can still perform highly accurate TC measurement due to the influence of the external environment such as temperature and humidity and the influence of toner lot blurring. It was a problem.
Therefore, the present invention has been made in view of the above problems, and its problem is to suppress measurement errors between sensors and apparatuses, extremely reduce the influence of toner deterioration over time, and perform highly accurate TC measurement. And a process cartridge and an image forming apparatus including the developing device.

The features of the present invention, which is a means for solving the above problems, are listed below.
The present invention relates to a two-component electrophotographic developing device, wherein the developing device has a magnetic permeability sensor for measuring a toner concentration, and developers having two or more different toner concentrations at the start of use of the developing device. The developing device is characterized in that adjustment of the sensor is performed using

  The present invention is the developing device as described above, wherein the developing device has two or more different types of toner developers in the developing device, and each can independently move to the stirring region. .

The present invention is the developing device described above, wherein the developing device adjusts the sensor while changing the toner density of the developer.

According to the present invention, in the developing device described above, the developing device adjusts the sensor while mixing developers having different toner concentrations.

The present invention is the above-described developing device, wherein the developing device adjusts the sensor while replenishing the toner.

According to the present invention, in the developing device described above, the developing device adjusts the sensor while consuming toner.

The present invention is the developing device described above, wherein the developing device adjusts the sensor by separately measuring developers having different toner concentrations.

The present invention is a process cartridge in which a process cartridge integrally supports the developing device described above and a photosensitive member. According to the present invention, in the process cartridge described above, the process cartridge integrally supports at least one means selected from a charging means and a cleaning means. It is a bridge.

The present invention is an image forming apparatus characterized in that the image forming apparatus has the developing device described above. According to another aspect of the invention, an image forming apparatus includes the process cartridge described above.

  According to the means for solving the above-described problems, it has become possible to perform highly accurate TC measurement by measuring two or more TC-Vt and determining a TC-Vt straight line. In addition, it is possible to provide a high-quality image and an image forming apparatus having a high margin for problems such as toner scattering and carrier adhesion.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

1 and 2 show the outline of the developing device, and the developer containing toner moves in the direction indicated by the arrow in FIG. FIG. 2 is a sectional view of the developing device, showing a state before use. The seal member 7 can be pulled out from the developing device. When the seal member 7 is pulled out during use, the developer 6 falls on the transport screw 4 and is transported to the developing roller 5 and stirred by the transport screw 4. Here, the TC in the developing device is measured by a magnetic permeability type concentration sensor 3 (hereinafter referred to as a sensor) attached to the lower portion of the developing device. The sensor 3 has an input of a control voltage (hereinafter referred to as Vcnt) in addition to an input for power supply, and sends an output (hereinafter referred to as Vt) to the image forming apparatus according to TC. The relationship between TC and Vt is approximated by a linear expression having a negative slope as shown in FIG. Further, Vt can be shifted by changing Vcnt.
Therefore, Vt is adjusted to a target value by changing Vcnt using an initial agent whose TC is known. Based on this result and the slope (sensitivity) of TC-Vt determined by the circuit design of the sensor 3, the relationship between TC and Vt is determined, and thereafter the value of TC is measured from the value of Vt.

However, the sensitivity of the sensor varies greatly from individual to individual, and a sensitivity tolerance of about ± 20% is required from the viewpoint of productivity. Therefore, as shown in FIG. 4, the TC variation with respect to Vt increases as the distance from the TC of the initial agent increases. FIG. 4 shows a situation when Vt changes by 1V after adjusting with 7% developer for the sensor 3 having a sensitivity tolerance of ± 20%.
As a countermeasure, the sensitivity of the sensor 3 is measured as shown in FIG. 5 by measuring at least two points of Vt with respect to a known TC, and thereafter, TC is estimated from Vt using a straight line passing through the measurement point. And In FIG. 5, two points where TC-Vt is measured are plotted with squares, and a straight line passing through them is determined. When measuring at three or more points, the sensitivity of the sensor 3 is determined by performing linear approximation on each point.
As a result, the sensitivity of the sensor 3 is not a value having a large width determined by circuit constants, but can be determined from the sensitivity to the actual developer 6, so that TC measurement can be performed with high accuracy.

  Here, a method for measuring two points at TC-Vt of the present invention will be described. It is possible to measure two or more points by setting different TC developers in the developing device so that they can be put out independently on the conveying screw. A set example of the developer 6 at this time is shown in FIG. In FIG. 6, the lower seal A is first pulled to the right, the developer 1 is dropped, the sensor Vcnt is adjusted, the seal B is similarly pulled out, the developer 2 is dropped, and Vt is measured again. Take a second measurement. Although two types of developer are used in FIG. 6, it is possible to measure the sensitivity from a number of points by dividing into three or more types.

Next, a case where two types of developers are set as in the present invention will be described. As an example, developer 1 is 6% at 250 g, and developer 2 is 18% at 50 g. At this time, the seal A is removed and Vcnt adjustment is performed using 6% of the developer 1 to obtain the first Vt. Next, after removing the seal B, if it is sufficiently stirred, the developer becomes 8% at 300 g. Therefore, by measuring Vt, Vt outputs of 6% and 8% can be obtained, so that the sensitivity of the sensor 3 can be obtained.

Next, contrary to the above example, when the amount of the developer 1 is decreased and the developer 2 is increased, most of the developer 1 dropped first is adsorbed on the developing roller by stirring. Therefore, if the developer 1 is 12% at 50 g and the developer 2 is 6% at 250 g, the sensor 3 immediately after removing the seal A outputs 12%, but most of it moves on the developing roller by stirring. Then, the developer on the sensor 3 disappears. When the developer 2 is injected by removing the seal B, the sensor 3 outputs 6%. Therefore, since 6% and 12% Vt outputs can be obtained, the sensitivity of the sensor 3 can be obtained from the values of two points as in the above example.

  Further, the TC in the developing machine is kept constant (one type), and after adjusting Vcnt, the TC is changed within a range that can be understood, and the sensitivity of the sensor 3 can be obtained together with the Vt output at that time. As an example of the present invention, when the TC of the developer set in the developing device is 6% at 300 g, and then 10 g of toner is replenished in the developing device, the TC is about 9%. Therefore, by measuring the Vt output, 6% and 9% Vt outputs can be obtained, so that the sensitivity of the sensor 3 can be obtained.

  It is also possible to reduce the TC and obtain the sensitivity of the sensor 3 by performing a constant image formation without replenishing the developing device. Specifically, if the developer is 300% at 300 g, the toner consumption of 9.5 g is about 6%. Therefore, it is possible to measure the sensitivity of the sensor 3 by the above method by measuring in advance how much 9% of the developer consumes 9.5 g of toner.

  Further, the developing device can be combined with a photosensitive member, a charging device, a cleaning device, and the like to form a process cartridge. Specifically, there is a process cartridge in which the developing device and the photosensitive member shown in FIG. 1 are integrated. Furthermore, the charging means and the cleaning means can be integrated.

The developing device and the process cartridge described above can also be used in an image forming apparatus. FIG. 7 is a diagram showing an image forming apparatus of the present invention. The development system employs a dry two-component development system, and the system is a full color machine of a quadruple tandem type intermediate transfer system. However, this is given as a representative example of an image forming apparatus, and any other configuration or method is not limited as long as it is a dry two-component development method.
First, an image forming operation will be described. When a print start command is input, the rollers around the photosensitive member 11 as the latent image carrier, around the intermediate transfer belt 18 and the paper feeding / conveying path start to rotate and from the lower paper feeding tray 29 to the recording paper Sheet feeding starts. The surface of each photoconductor 11 is charged to a uniform potential by a charging charger 12 as a charging means, and the surface is exposed according to image data by writing light emitted from a writing unit 13 as an exposure means. .

The potential pattern after exposure is called an electrostatic latent image. The photosensitive member 11 carrying the electrostatic latent image on the surface thereof is carried by supplying toner in a dry two-component developing unit. The electrostatic latent image is developed to a specific color. In FIG. 7, since there are four photosensitive members 11, toner images of yellow, magenta, cyan, and black (color order varies depending on the system) are developed on each photosensitive member 11. The toner image developed on the photoreceptor 11 is intermediated by a transfer bias and a pressing force applied to a primary transfer roller 15 serving as a transfer unit disposed opposite to the photoreceptor 11 at a contact point with the intermediate transfer belt 20. The image is transferred onto the transfer belt 20. By repeating this for the four colors while matching the timing, a full-color toner image is formed on the intermediate transfer belt 20 as an image carrier.
The full-color toner image formed on the intermediate transfer belt 20 is transferred onto the recording paper conveyed by the registration roller 24 in time. At this time, transfer is performed by the secondary transfer bias applied by the secondary transfer roller 21 and the pressing force. The recording paper to which the full color toner image has been transferred passes through the fixing unit 22, whereby the toner image carried on the surface is heated and fixed.

  If it is single-sided printing, it is conveyed straight as it is to the paper discharge tray 23, and if it is double-sided printing, the conveyance direction is changed downward and conveyed to the paper reversing unit. The recording paper that has reached the paper reversing section is reversed in the transport direction by the switchback roller 25 and exits the paper reversing section from the rear end of the paper. By this operation, the front and back of the recording paper can be reversed. The recording paper that is turned upside down does not return to the fixing unit 22 but passes through the refeeding path and joins the original feeding path. Thereafter, the toner image is transferred in the same manner as the front surface printing, and is discharged through the fixing unit 22. This is a double-sided printing operation. The operation of each part will be described to the last. The photoreceptor 11 that has passed through the primary transfer part carries the primary transfer residual toner on the surface thereof, and this is removed by the photoreceptor cleaning unit 16. Thereafter, the surface is uniformly discharged by a QL (quenching lamp) 17 to prepare for charging for the next image. The intermediate transfer belt 18 that has passed through the secondary transfer portion also carries secondary transfer residual toner on its surface, which is also removed by the intermediate transfer belt cleaning unit to transfer the next toner image. Prepare for. By repeating such an operation, single-sided printing or double-sided printing is performed.

It is the figure which showed the image development apparatus. It is the figure which showed sectional drawing of the image development apparatus. It is the figure which showed the relationship between TC and Vt. It is the figure which showed the relationship between TC and Vt. It is the figure which showed the relationship between TC and Vt. FIG. 6 is a diagram illustrating an example of setting a developer 6. 1 is a diagram showing an image forming apparatus of the present invention.

Explanation of symbols

1 Developer 1
2 Developer 2
3 Concentration sensor 4 Conveying screw 5 Developing roller 6 Developer 7 Seal member 8 Developing device A Seal A
B Seal B
11 Photoconductor 12 Charging Charger 13 Writing Unit 15 Primary Transfer Roller 16 Photoconductor Cleaning Unit 17 QL (Quenching Lamp)
18 Intermediate transfer belt 20 Intermediate transfer belt 21 Secondary transfer roller 22 Fixing unit 23 Paper discharge tray 24 Registration roller 25 Switchback roller 29 Paper feed tray

Claims (11)

In a two-component electrophotographic developing device,
The developing device has a magnetic permeability type sensor for measuring a toner concentration, and adjusts the sensor by using two or more types of developers having different toner concentrations at the start of use of the developing device. apparatus. The developing device according to claim 1,
2. The developing device according to claim 1, wherein the developing device has two or more different types of developer in the developing device, and each of the developing devices can be independently moved to the stirring region. The developing device according to claim 1 or 2,
The developing device, wherein the developing device adjusts a sensor while changing a toner density of the developer. In the developing device according to claim 3,
The developing device, wherein the developing device adjusts a sensor while mixing developers having different toner concentrations. In the developing device according to claim 3,
A developing device, wherein the developing device adjusts a sensor while replenishing toner. In the developing device according to claim 3,
A developing device, wherein the developing device adjusts a sensor while consuming toner. In the developing device according to claim 1 or 2,
2. A developing device according to claim 1, wherein the developing device adjusts the sensor by separately measuring developers having different toner concentrations. A process cartridge, wherein the process cartridge integrally supports the developing device according to any one of claims 1 to 7 and a photosensitive member. The process cartridge according to claim 8, wherein
A process cartridge, wherein the process cartridge integrally supports at least one means selected from a charging means and a cleaning means. An image forming apparatus comprising the developing device according to claim 1. An image forming apparatus comprising the process cartridge according to claim 8 or 9.

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