JPH1165244A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep image quality constant in spite of the deterioration of developer even when the kind of the developer is changed by applying a developing bias based on the output information of a developing bias parameter setting means to a developer carrier by developing bias power source. SOLUTION: A counter outputs the number of prints and the summed-up operation time of a device to transmit them to an overall control part. The overall control part calculates a bias parameter based on data from a developer information part and the output data of the counter to transmit the bias parameter to bias supply. In this bias supply, the peak-to-peak voltage value of a bias is periodically set on the basis of the data of the bias parameter, a waveform is formed and amplifying to a high voltage is attained, to apply the bias to the developing sleeve of a developing device with fixed timing. Therefore, a proper bias is developed/applied from an estimate of the deterioration pattern and present deteriorated state of the developer, so that the quality of the image such as dot uniformity can be always kept in a constant state.

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 such as an electrophotographic copying machine, a laser printer, and a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus employing an image forming method such as an electrophotographic copying method or an image recording method, an electrostatic latent image is formed on an image carrier such as a photoreceptor, and the electrostatic latent image is developed. The toner image is developed by the device. In this type of image forming apparatus, a toner image on the image carrier is fixed on the image carrier as it is, and the toner image on the image carrier is transferred to a transfer material such as transfer paper. The one fixed on the transfer material, the one which transfers the toner image on the image carrier to an intermediate transfer member such as an intermediate transfer belt, and further transfers the toner image from the intermediate transfer member to the transfer material, and then fixes the toner image on the transfer material. is there. As a developing device for visualizing an electrostatic latent image on an image carrier, a two-component developer composed of toner and carrier is used, and an alternating electric field is applied to a developing region where the image carrier and the developer carrier are opposed to each other. There is known a device that performs development by forming a developing bias electric field having the same.

[0003] Two-component development using a two-component developer is known as a developing method which is particularly excellent in high-speed responsiveness in an image forming method using an electrophotography or other powder toner, and particularly, a copier, a laser printer or the like. Is used as a mainstream technology in the product field. In the two-component developing method, the developer is held and conveyed on the surface of a non-magnetic sleeve with a built-in magnet as a developer carrier, and the developer is made into a brush shape (a so-called magnetic brush). The toner is selectively adhered to the latent image surface by an electric field between the image carrier on which the electrostatic latent image is formed and the sleeve to which the electric bias is applied, so that the development is performed. According to the study by the inventors, it is clear that toner can be more faithfully attached to a latent image when a bias having a periodic waveform is applied to the sleeve.

[0004] The carrier constituting the two-component developer is a magnetic material, and is held and conveyed on the sleeve surface by a magnet inside the sleeve. On the other hand, the toner has a charge when it comes into contact with the carrier, moves with the carrier, and is transferred to the image carrier according to the electrostatic latent image and consumed. Usually, the toner corresponding to the consumed amount is newly supplied to the developing device. The carrier stays in the developing device, is mixed with the supplied toner, and contributes to the conveyance and charging of the toner. Examples of the carrier include a carrier obtained by coating a core material of a magnetic substance such as iron powder, ferrite, and magnetite with a resin, and a carrier obtained by dispersing magnetite fine powder or the like in a resin (binder). The resistance of the carrier is controlled to an appropriate value by these coating materials and the binder, and the durability of the carrier is improved.

[0005]

However, the carrier is stressed by the operation of the developing device for a long time,
The coating material is scraped or a part of the substance constituting the toner adheres (spent). If the coating layer of the coating carrier is scraped or peeled off, the carrier resistance decreases, and the developing bias applied to the sleeve leaks to the image carrier, so that the developing bias cannot be maintained and development cannot be performed. Further, the electrostatic latent image on the image carrier is destroyed. On the other hand, when the carrier is spent, the charge amount of the toner decreases, and the toner adheres to the background portion or the toner scatters, while the toner does not sufficiently adhere to the image portion. Under these conditions, it is difficult to continue using the carrier, and the time until such a situation is reached is generally called the life of the carrier. Whether the coating layer of the carrier is scraped or peeled off by using the developer for a long time,
Whether the spent occurs depends on the material properties of the toner and the carrier, and both may proceed at the same time. In any case, the deterioration of the developer cannot be avoided, but the fluctuation of the image quality due to the deterioration cannot be neglected.

In an image forming apparatus employing a two-component developer and a developing device which performs development by forming a developing bias electric field having an alternating electric field in a developing region, deterioration of image quality due to a change in carrier resistance is prevented. For example, in Japanese Patent Application Laid-Open No. 5-66654, a reference toner image is formed on an image carrier, and the reference toner image is read by an optical sensor to detect the degree of edge emphasis. It has been proposed to change the peak-to-peak voltage value. In Japanese Patent Application Laid-Open No. Hei 6-214451, the charge amount of toner in a developing device, the amount of toner adhered on an image carrier, the toner concentration of developer, the electrical resistance of developer in a developing device, and the like are detected. It has been proposed to control a developing bias including an AC component according to the result.

[0007] Each of these techniques is a method of estimating the deterioration state of the two-component developer with some characteristic value. However, it is inevitable that the measured values of these characteristics have variations, which may reduce the accuracy of estimating the deterioration state. In some cases, the control system may run away. Factors of variation include (including degradation)
There may be various things, such as a failure of the detection means, a change in the detection value due to environmental conditions, a displacement of the mounting position of the detection means, and noise on the detection value due to electromagnetic waves, and these may have a combined effect. As a result, image forming conditions that do not match the state of the developer are set, and various images such as excessive or insufficient image density, toner and carrier adhesion to the background, detachment of the edge, and appearance of sweeping by a magnetic brush Causes deterioration. Further, when the components of the apparatus are worn or contaminated with scattered toner, the image forming apparatus may be damaged and the service life may be shortened.

The present invention solves the above-mentioned conventional problems, and has devised an image forming apparatus capable of maintaining a constant image quality irrespective of deterioration even when the type of developer changes. The task is to

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided an image carrier having photoconductivity, a latent image forming apparatus for forming an electrostatic latent image on the image carrier, and a two-component developing apparatus. A developing device having a developer carrier for holding and transporting the developer, wherein the developing device selectively adheres the toner on the developer carrier to the electrostatic latent image formed on the image carrier and develops the toner; An image forming apparatus comprising: a developing bias power supply for applying a developing bias that changes periodically to a developer carrier; and a storage unit for storing an integrating operation time of the developing device; and an integrating operation of the developing device. Developer information storage means which shows a tendency for developer characteristics to change with time; and development bias parameter setting for setting development parameters including a peak-to-peak voltage value of the development bias from information in these storage means and the developer information storage means. Means With, the developing bias power supply by arranging for applying a developing bias based on the output information of the developing bias parameter setting means to the developer carrying member, is solved.

It is preferable that the developer information storing means is capable of giving developer information as a relationship between a voltage applied to the developer and a resistance value at that time. The storage device and the developer information storage device are provided in the detachable developing device, and the information in the storage device and the developer information storage device is read when the developing device is mounted. Is more effective. And optionally,
At least a detachable unit having the image carrier and the developing device is provided with the storage unit and the developer information storage unit, and the storage unit and the developer information storage unit are mounted when the unit is mounted. It is equally effective to read information.

[0011]

FIG. 1 shows the basic structure of an image forming apparatus. At the center is a drum-shaped organic photoreceptor (OPC) 1, which rotates in the direction of the arrow. Along the moving direction of the photoreceptor 1, uniform charging by the charging roller 2, writing of LD light by the image exposure device 3, development by toner stored in the developing device 4, transfer to a transfer material by the transfer device 5, cleaning The cleaning of the photoreceptor 1 by the device 6 and the image forming process proceed, and the transfer material is separated from the photoreceptor 1 and then fixed by the fixing device 7 with toner.

As a result of the research by the inventor, when an appropriate periodic bias (AC bias) is applied to the two-component developer, the concentration of dots is increased, and the uniformity of the image and other overall quality are improved. It became clear. FIG. 2 shows an example of the effect. This graph shows the results of evaluating the uniformity of dots by applying a bias that amplifies a rectangular wave to a developer carrier (hereinafter, referred to as a sleeve) of a developing device. Voltage,
The vertical axis shows the dot area variation (standard deviation divided by the average value). The dot area was obtained by reading an image enlarged by a metallographic microscope with a CCD camera, converting the image into image data, and detecting the image data with image analysis software. Two kinds of developers A and B are used, and they use the same toner. The carrier has a common core material (magnetite) with a coating layer (silicone resin) thickness of 0.4 μm.
(A) and 0.8 μm (B). According to FIG. 2, it can be seen that the larger the peak-to-peak voltage, the smaller the variation in dot area, and the more uniform the image.

In order to clarify the difference between the two types of developers A and B, their resistances were measured. As a measuring method, a developer sample was placed in a cylindrical container, packed under a predetermined condition, a voltage was applied between the bottom surfaces, and a resistance was obtained from a flowing current value. The results are shown in FIG. From the data of other samples, it is clear that the tendency of the resistance to decrease with applied voltage is general.

2 and 3, the peak-to-peak voltage Vpp of the AC bias is increased when the resistance of the developer is increased, and the peak-to-peak voltage Vpp is increased when the resistance of the developer is decreased. Is assumed to be constant so that constant dot uniformity is always obtained. From another viewpoint, image quality can be stabilized by changing the applied voltage so that the resistance becomes constant.

FIG. 4 shows the relationship between the time of forcibly stirring the developer and the resistance value at a specific applied voltage. Curve I shows a tendency for the resistance to decrease with stirring time, and curve II shows the opposite. When the carrier was analyzed, it was found that the curve I was of a type in which the thickness of the coat layer was gradually reduced with stirring and the curve II was of a type in which spent occurred.

As described above, the manner of changing the resistance varies depending on the type of the developer. In the present invention, the tendency of the resistance of each developer usable in the developing device to change is programmed in advance, and the peak-to-peak voltage value of the oscillation component of the developing bias is changed accordingly. When the developer is replaced, the pattern of deterioration (change in resistance) of the new developer is also switched at the same time, so that an optimum developing bias is always applied to all types of developers to maintain a constant image quality. be able to.

Hereinafter, a specific configuration example will be described.
FIG. 5 is a sectional view of the developing device. As is known, the developing device 4 includes a developing sleeve (developer carrier), a doctor blade, an internal magnet, a stirring member, and the like. Developing sleeve 1
Numeral 1 is made of a non-magnetic conductive member, and its surface is provided with appropriate unevenness by sandblasting or the like. The developing sleeve 11 rotates in the direction of the arrow, and has a plurality of fixed magnets 13 therein.
Is provided. A developing bias is applied to the developing sleeve 11 from a bias power supply 16 as described later. Two agitating members 14 for moving the developer in opposite directions (in both directions perpendicular to the paper surface) are provided in the developer reservoir.
Are arranged. A doctor blade 1 for regulating the amount of developer transported to the developing area is provided near the developing sleeve.
2 are provided.

When the toner is consumed, a corresponding amount of toner is supplied from a toner bottle (not shown). The replenished toner is mixed with the developer in the developing device by the stirring member 14. When the developer conveyed by the two stirring members 14 reaches the vicinity of the developing sleeve, it is pumped up to the developing sleeve 11 by the action of the internal magnet 13.
A convection phenomenon of the developer occurs on the downstream side of the doctor blade 12, the toner and the carrier are uniformly mixed, and the toner is sufficiently and uniformly charged. Doctor blade 12
Due to the gap between the developing sleeve 11 and the developing sleeve 11, the amount of the developer conveyed to the developing area becomes constant.

The developing area, in other words, the developing sleeve 1
1, in a region where the toner can move to the image carrier 1 on which the electrostatic latent image is formed, the magnetic brush formed by the magnet 13 contacts the image carrier 1, and the voltage of the developing sleeve 11 and the image carrier 1 The toner moves to the image carrier side due to the electric field formed between the electrostatic latent image and the electrostatic latent image.

FIG. 6 shows the waveform of the developing bias applied to the developing sleeve. The horizontal axis represents time, and the vertical axis represents a voltage value with the direction in which the toner receives a force directed toward the image carrier taken upward. The voltage value when the toner receives the maximum force toward the image carrier is V1, the voltage value when the toner receives the maximum force toward the development sleeve 11 is V0, the time during which V1 is maintained is t1, and the period is t2. And The integrated average Va of the voltage value is -500 V to -70 as in a normal DC bias.
It is set to about 0V. Where Va = V0 + (V1-V
0) t1 / t2.

As the developer, for example, a carrier in which ferrite particles having a particle size of 50 μm are used as a core material and the surface thereof is coated with a silicone resin, and a thermoplastic resin having a mass average particle size of 7.5 μm and colored with carbon black are used. A mixture of a resin and a toner as a main component at a toner concentration of 5 wt% (mass ratio: carrier: toner: 95: 5) is used.

When the developer is set in the developing device for the first time, or when all the developer is exchanged, the operation of the device becomes possible only after a service person or an operator who is a user performs a procedure for inputting developer information. As such, a control system is set up.

FIG. 7 is a block diagram of control of the image forming apparatus. The counter outputs the number of prints or the accumulated operation time of the apparatus and sends it to the overall control unit. The overall control unit calculates a bias parameter based on the data from the developer information storage unit and the output data of the counter, and sends it to the bias power supply. The bias power supply sets a peak-to-peak voltage value of the periodic bias based on the data, forms a waveform, amplifies the voltage to a high voltage, and applies it to the developing sleeve of the developing device at a predetermined timing.

FIG. 8 is a flowchart of the control contents performed by the overall control unit. Whether the developer is set in the developing device is detected by using, for example, an optical element or a piezoelectric element, and if it is not set, it does not operate until set, and if set, the developer information is input. Check if it has been completed, and if not, request input. Subsequently, the developer information and the counter are read, a bias parameter (peak-to-peak voltage value) is determined from the relationship, and the bias parameter is output to a bias power supply. Next, the control is transferred to the image forming sequence control section to perform the image forming sequence.

The developing bias power source has an integral average value Va of -600 V as a developing bias and a vibration component of a frequency of 5 kHz.
z, the duty ratio is fixed at 20%, and the peak-to-peak voltage is set to a value indicated by the overall control unit. The range is 1
A range from kv to 3 kv is preferred.

The operation when two types of developers I and II are set in the image forming apparatus having the above configuration will be described. The developer I is deteriorated as the coat layer of the carrier is scraped by repeated use (I in FIG. 4).
Equivalent). Immediately after setting the developer in the developing device, the operator inputs the type name of the developer from the ten keys. As a result, the table is referred to and stored in the memory as developer information. This developer information has a relationship between the accumulated operation time and the parameter of the developing bias to be set. In this case, the bias value is set so that the peak-to-peak voltage becomes gradually lower as the developer is used. As a result, the dot uniformity is always kept constant. Developer
II indicates that the carrier is spent and deteriorates by repeated use (corresponding to II in FIG. 4).
Similarly, by operating the numeric keypad immediately after setting the developer in the developing device, the developer information is input to the memory. Similarly, the developer information has a relationship between the accumulated operation time and the parameter of the developing bias to be set. In this case, the bias value is set so that the peak-to-peak voltage becomes higher as the developer is used. As a result, the dot uniformity is always constant.

As described above, according to this embodiment, an appropriate bias is formed and applied based on the pattern of the deterioration of the developer and the estimation of the current state of deterioration, so that image quality such as dot uniformity is obtained. Can always be kept in a constant state. Here, since actual physical property values, such as the resistance of the developer, are not detected, but are estimated from data obtained in advance,
There is no room for a detection error or the like to enter, and stable control can be realized.

In the above-described image forming apparatus, the developing device may be configured to be detachable independently. FIG.
As shown in FIG. 7, the counter for storing the number of prints or the cumulative operation time of the developing device 4 described in the above example, and the developer information storage unit for storing the deterioration pattern of the developer are constituted by nonvolatile storage means 18. Then, it is detached integrally with the developing device. When the developing device 4 is mounted, the storage unit 18
Are connected to the image forming apparatus main body side via a connector, and the same circuit as that described with reference to FIG. 7 is formed. The following operation is the same as in the above example. In this embodiment, in addition to having the same operation and effect as the above example, even if a different type of developer is used in the course of replacement of the developing device, the developer deterioration pattern and the deterioration state in each developing device are not changed. Since they are stored in the non-volatile storage means integrated with the developing device, they can be detected without error and a developing bias corresponding thereto can be applied, so that a constant image quality can be obtained in any case.

In the above-described image forming apparatus, the developing device and the image carrier may form an integral image forming unit, and may be configured to be detachable from the main body. As shown in FIG. 10, a counter for storing the number of prints or the cumulative operation time of the developing device described in the first example,
The developer information storage unit for storing the deterioration pattern of the developer is constituted by a non-volatile storage unit 20, and is attached to and detached from the image forming unit 22. When the image forming unit 22 is mounted, the storage unit 20 is connected to the image forming apparatus main body side via a connector, and the same circuit as that described with reference to FIG. 7 is formed. The following operation is the same as in the first example. In this embodiment, in addition to the same operation and effect as the first example, by replacing the image forming unit,
Even if a different type of developer is used on the way, since the developer deterioration pattern and the deterioration state of each developing unit are stored in the non-volatile storage unit integrated with the developing unit, they are detected without error, and In this case, a constant image quality can be obtained in any case.

[0030]

According to the first aspect of the present invention, there is provided a developer information storage means for indicating that the developer characteristic tends to change in accordance with the integrated operation time of the developing device, and a storage means for storing the integrated operation time of the developing device. A developing bias parameter setting means for setting a developing parameter including a peak-to-peak voltage value of the developing bias from the information of the storage means and the developer information storing means. It is configured to apply a developing bias based on the developer to the developer carrier, so that the type of developer can be estimated by estimating the deterioration pattern of the developer and the current deterioration state, and applying a bias in accordance with them. Even if it changes, the image quality can always be kept constant.

According to the second aspect of the present invention, the developer information storage means can give the developer information as a relationship between the voltage applied to the developer and the resistance value at that time, so that the deterioration pattern of the developer can be improved. Is stored as a relationship between the voltage applied to the developer and the resistance value, and a stable control system without runaway can be realized. According to the third and fourth aspects of the present invention, even if a developing device or an image forming unit containing different types of developers is used in the middle, the storage unit is integrated with the developing device or the image forming unit. Therefore, a bias can be applied according to the deterioration pattern and the degree of deterioration of the developer in use, and the image quality can be constantly maintained.

[Brief description of the drawings]

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

FIG. 2 is a graph showing an evaluation of dot uniformity by applying a bias to a developer carrier of a developing device.

FIG. 3 is a graph showing a resistance change with respect to a peak-to-peak voltage corresponding to FIG. 2 in two types of developers.

FIG. 4 is a graph showing a relationship between a stirring time and a resistance value at a specific applied voltage while forcibly stirring a developer.

FIG. 5 is a schematic sectional view of a developing device.

FIG. 6 is a graph showing a waveform of a developing bias applied to a developing sleeve.

FIG. 7 is a control block diagram of the image forming apparatus.

FIG. 8 is a flowchart of control contents performed by an overall control unit.

FIG. 9 is a schematic perspective view of a detachable developing device.

FIG. 10 is a schematic configuration diagram of a detachable unit in which an image carrier and a developing device are integrated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 4 Developing device 11 Developing sleeve 12 Doctor blade 13 Magnet 14 Stirring member 16 Bias power supply

Claims (4)

[Claims] An image carrier having photoconductive properties, a latent image forming apparatus for forming an electrostatic latent image on the image carrier, and a developer carrier for holding and transporting a two-component developer. A developing device for selectively adhering the toner on the developer carrier to the electrostatic latent image formed on the image carrier for development, and applying a developing bias that periodically changes to the developer carrier; An image forming apparatus comprising a developing bias power supply
A storage unit for storing the accumulated operation time of the developing device; a developer information storage unit for indicating that the developer characteristic tends to change according to the accumulated operation time of the developing device; Developing bias parameter setting means for setting a developing parameter including a peak-to-peak voltage value of the developing bias from the information of the developing bias, wherein the developing bias power supply applies a developing bias to the developer carrier based on output information of the developing bias parameter setting means. An image forming apparatus characterized by applying. 2. The image forming apparatus according to claim 1, wherein said developer information storage means is provided with the developer information as a relationship between a voltage applied to the developer and a resistance value at that time. 3. The detachable developing device is provided with the storage means and the developer information storage means, and the information in the storage means and the developer information storage means is read when the development device is mounted. The image forming apparatus according to claim 1, wherein: 4. A detachable unit having at least the image carrier and the developing device is provided with the storage means and the developer information storage means. When the unit is mounted, the storage means and the developer The image forming apparatus according to claim 1, wherein information in a medicine information storage unit is read.