JPH05150600A - Method for adjusting surface potential and image forming device - Google Patents

Abstract

PURPOSE:To improve the operability at the time of adjustment by setting only a surface potential as a reference potential at the time of developing by a standard developer and obtaining an appropriate surface potential only by adjusting the reference potential according to the electrostatic characteristic of each developer when other developer is used. CONSTITUTION:Assuming that the absolute value of a surface potential of a photosensitive body is the same as that of a black toner Vo, the density gradation of a copied image by a red toner is shown by an attenuate long and short line A. the inclination at the center part of the line which affects density gradation is larger comparing with the ideal line B of the density gradation of the copied image by the black toner. In order to obtain the same degree of density gradation as that of the black toner, the inclination of the center part of the line A must approach to that of the dotted line B. The absolute value of the surface potential of the photosensitive body V1 is obtained by subtracting DELTAfrom the reference potential Vo to be (Vo-DELTA). Thus, by detecting the amount of red toner drawn o the photosensitive body, the density gradation is adjusted.

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 capable of color copying with a plurality of developers, which adjusts the surface potential of a photosensitive member during charging according to each developer. The present invention relates to a method and an image forming apparatus that charges a photoconductor using a charging device adjusted by this adjusting method.

[0002]

2. Description of the Related Art In a conventional color image forming apparatus such as an image forming apparatus such as a copying machine, when a plurality of developers are used for development, the gradation property of density is caused by the difference in electrostatic characteristics of the developers. In order to correct the variation of the surface potential of each developer, the surface potential is adjusted individually while taking into account the charging characteristics peculiar to each developer when it is installed in the main body of the device and the electrostatic characteristics peculiar to each developer. Had been set.

[0003]

Conventionally, the surface potential of the photosensitive member has been individually adjusted by charging in consideration of the charging characteristic peculiar to the photoreceptor and the electrostatic characteristic peculiar to the developer for each developer. .. Therefore, there is a problem that the adjustment operation during the manufacturing process takes time. Moreover, in a device such as a single color copying device in which a plurality of developing devices for accommodating various developers are exchanged and used as needed, due to an increase in the types of the developers due to the expansion of functions, Since the work of adjusting the surface potential is also increased and it takes a lot of time to adjust it, there is also a problem that the number of developers that can be used is limited and the expansion of functions is hindered.

In view of the above, the present invention eliminates the above-mentioned problems, and adjusts the surface potential of the photoreceptor at the time of charging individually while considering the charging characteristics of the photoreceptor and the electrostatic characteristics of the developer for each developer. There is no need, and even if there are many developers to be used, the surface potential can be adjusted to suit each developer in a short time, and it is possible to use various kinds of developers and expand their functions. An object of the present invention is to provide a surface potential adjusting method and an image forming apparatus which are excellent in operability and functionality.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention forms an image carrier by a plurality of developing devices each containing a developer having different electrostatic characteristics including a reference developer. In the apparatus for developing an electrostatic latent image, the surface potential of the image carrier by the charging means required during development with the reference developer is used as a reference potential, and is different from the reference developer among the plurality of developers. When developing with an arbitrary developer, the reference potential is adjusted according to the electrostatic characteristics of the arbitrary developer.

In order to solve the above problems, the present invention can be installed in an apparatus main body having an image carrier, charging means for charging the image carrier to an arbitrary surface potential, and a developing position of the image carrier. And a plurality of developing devices that respectively store any developers having different electrostatic characteristics including a reference developer and selectively develop the electrostatic latent image formed on the image carrier, At the time of development by a developing device containing a developer, the charging means is controlled so that the surface potential of the image carrier is set to a reference potential necessary for development, while the reference developer among the plurality of developers is A control means is provided for controlling the charging means so as to adjust the reference potential in accordance with the electrostatic characteristics of the arbitrary developer during development by an arbitrary developing device accommodating a different arbitrary developer.

[0007]

The present invention is configured as described above, and if only the surface potential at the time of developing with the reference developer is set and this is used as the reference potential, in the case of other developers, the It is necessary to individually adjust the surface potential of the photoconductor for each developer in consideration of the photoconductor and the electrostatic properties of the developer, because an appropriate surface potential can be obtained simply by adjusting the reference potential according to the electric property. Even when there is no image formation with many developers,
It does not take time to adjust the surface potential of the photoconductor for each developer, and the operability in adjusting the surface potential during manufacturing is improved. Consequently, it is possible to use a large number of developers and expand its functions. Will also be possible.

[0008]

EXAMPLES The principle of the present invention will now be described. First, for example, a black developer having a black toner having a specific resistance of 15 × 10 ¹⁰ [Ωcm] and a specific resistance of 60 × 10
^The charge amount with respect to the stirring time, which is the electrostatic characteristic of the red developer having the red toner of ¹⁰ [Ωcm], is shown by the solid line (a) and the chain line (b) in FIG. 4, respectively.
That is, while the stirring time is short (before T1), the red toner having a high specific resistance has a lower charge amount than the black toner having a low specific resistance, and when the stirring time T1 is reached, the toner of both toners is reduced. As the charge amount reverses and the stirring time becomes longer,
While the charge amount of the black toner is stable, the red toner is
Has a characteristic that the charge amount of is further increased and becomes stable.

On the other hand, when the toner has a large charge amount, the toner is
In addition, the attracting force between the carriers is large and it is difficult for the toner to attach to the photoreceptor side. On the contrary, when the toner charge amount is small, the toner is
In addition, the attraction force between the carriers is small, and the toner is easily attracted to the photoconductor side.

Therefore, for example, the stirring time of the developing device is T0.
At the point of time, as can be seen from FIG. 4, the charging amount of the black toner is about 10 [μC / g], while the charging amount of the red toner is about 7 [μC / g], so if both When both the absolute value of the surface potential on the photoconductor during development by the toner is set to [V0] suitable for the black toner, the red toner having a low charge amount is attracted by the photoconductor more than the black toner. The copy image tends to be too dark, and the copy image becomes too dark with respect to the original image.

That is, as shown in FIG. 5, when the absolute value of the surface potential of the photoconductor is set to the same [V0] as that of the black toner, the gradation of the density of the copy image by the red toner is represented by the one-dot chain line [A]. ]
As shown in, the slope of the central straight line portion that most affects the gradation of the density becomes larger than the dotted line [B] which is the ideal straight line of the density gradation of the copy image by the black toner. I will end up. Therefore, in order to obtain the gradation of the same density as that of the black toner, it is necessary to make the inclination of the straight line portion in the center of the alternate long and short dash line [A] close to the dotted line [B]. Therefore, in the present invention, the absolute value [V1] of the surface potential of the photoconductor during development with the red toner is reduced by [Δ] from the reference potential [V0],
By setting [V0-Δ], the amount of red toner attracted to the photoconductor is reduced and the gradation of density is adjusted.

The surface potential of the red toner [V1]
Is [V1 = V0−Δ = V0 × α]. However, the coefficient [α] depends on the electrostatic characteristics of the red toner, and when the stirring time is between 0 and T1, 0 <α <1,
When the stirring time is T1 or more, α> 1.

When the surface potential of the photoconductor at the time of development with a red toner is [1 = V0 × α], the gradation of the density of the copy image becomes as shown by the solid line [C], and the center The inclination of the straight line portion approaches the dotted line [B] and approaches the gradation of the density of the copy image by the black toner.

The present invention will now be described with reference to the embodiments shown in FIGS. FIG. 1 is a schematic explanatory view of the entire apparatus. A drum-shaped photoconductor 12 which is an image bearing member is provided at a substantially central portion of a device main body 10. Around the photoconductor 12, a rotational direction thereof is provided. Control device 4 which will be described later in sequence
The applied voltage is controlled by the charging transformer 51 controlled by 1. The charging device 13 is a charging device for adjusting the surface potential of the photoconductor 12, and the exposure position 14 by the exposure device 14.
a, reference developer, specific resistance 15 × 10 ¹⁰ [Ω ·
cm], a first developing device 16a for developing with a black developer having a black toner, and a specific resistance of 60 × 10 ^10.
Any one of the second developing devices 16b that develops with a red developer having a red toner of [Ω · cm] is replaceably attached to a developing position 16, a transfer peeling charger 17,
A cleaning device 18 and a static elimination lamp 20 are provided.

The surface potential of the photoconductor 12 by the charging device 13 when developing with a black toner is the main body 1 of the device.
In the production of No. 0, the electrostatic characteristics of the developer composed of the black toner and the carrier as well as the charging characteristics of the photoconductor 12 in the state of being attached to the apparatus main body 10 are taken into consideration for the adjustment. On the other hand, the surface potential of the photoreceptor 12 when developing with a red toner depends only on the electrostatic characteristics of the developer consisting of the red toner and the carrier, based on the surface potential of the black toner that has already been adjusted. It is adjusted according to the coefficient.
A connector (not shown) is provided on the rear side of each of the developing devices 16a and 16b for identifying each toner stored therein.
And the developing device 16a, 16b
Detection device (not shown) that reads each connector when mounting
Is provided. Further, on the right side of the apparatus main body 10, sheet feeding cassettes 21a and 21b for accommodating the sheet P and a manual sheet feeding table 21c are provided. And the device body 10
Inside the paper feed cassettes 21a, 21b and the manual paper feed tray 21c, pickup rollers 22a, 22b, 22c are provided.
The sheet of paper P taken out and fed by the photoconductor 12
A conveying path 24 for the sheet P that leads to the sheet discharge tray 23 on the left side of the apparatus main body 10 via the above is formed. First and second separation rollers 25a and 25b and a pair of registration rollers 26 are provided on the upstream side of the photoconductor 12 in the transportation path 24, and a transportation belt 27 and a fixing roller pair are provided on the downstream side. 28, Discharging roll
La pairs 30 are provided. A document table 31 which is a document placing means and a document cover 32 which covers the document table 31 are provided on the upper surface of the apparatus body 10.

Next, the control device 41 which is the control means will be described. On the input side of the control device 41, a detection device for detecting each operation key 43 on an operation panel (not shown) and connectors (not shown) of the first and second developing devices 16a and 16b via an input interface circuit 42. And the transport path 24
Various switches / sensors such as sheet detection switch inside sheet 4
4 etc. are connected. On the output side of the control device 41,
A display device 47 on the operation panel (not shown), the photoconductor 12 and the developing device 16 via the output interface circuit 46.
a, 16b, each driving motor 48 such as various rollers, the transfer peeling charger 17, the charge removing lamp 20, and the like driver 5
0, and the charging transformer 51 of the charging device 13 and the like are connected.

The charging transformer 51 applies a voltage to the charging device 13 according to the type of toner in the first and second developing devices 16a and 16b. That is, the control device 4
Reference numeral 1 denotes a ROM (read only memory) 52 for storing normal control, and a surface potential of the photoconductor 12 at the time of development by a black toner, which is adjusted at the time of manufacturing the apparatus main body 10. The black toner adjustment area 53a for storing the reference potential [V0] and the surface potential of the photoconductor 12 at the time of development by the red toner based on the reference potential stored in the black toner adjustment area 53 are adjusted. Nonvolatile RAM (random access memory) 5 including a red toner adjustment area 53b for storing the coefficient [α] and other areas 53c
3 is connected.

Next, the operation will be described. First, the device body 1
At the time of manufacturing 0, in consideration of the charging characteristic of the photoconductor 12 and the electrostatic property of the black toner in the state where the photoconductor 12 is incorporated in the apparatus main body 10 in order to correct the variation in the gradation of the image density, The surface potential of the photoconductor 12 at the time of development by the toner is adjusted, and the surface potential [V0] thus obtained is stored as a reference potential in the black toner adjustment area 53a of the nonvolatile RAM 53. On the other hand, in the case of the red toner, the coefficient [α] for adjusting the reference potential, which is the surface potential at the time of development by the black toner, according to the electrostatic characteristics of the red toner is set in the red toner adjustment area. It is stored in 53b.

When the power source (not shown) is turned on at the start of use after the apparatus main body 10 thus set is installed, the preheat of the fixing roller 28 is started and the control device 41 Is one of the developing devices 16 to be mounted.
The toner in a and 16b is a black toner or a red toner.
Is detected by an input from a detection device (not shown). Then, for example, when it is recognized that the first developing device 16a has a black toner, the nonvolatile RAM
Data from the black toner adjustment area 53a of 53 causes the surface potential of the photoconductor 12 by the charging device 13 to be [V
0] to control the charging transformer 51. After that, when the preheat of the fixing roller 28 is completed, the apparatus main body 10 is made ready for copying.

Next, the operator places the document D on the document table 31, and from each operation key 43 on the operation panel (not shown), an image of the sheet size, the copy magnification, the number of copies, etc. is displayed. When the forming condition is set and the copy key is turned on, the copy operation is started.

As a result, in the apparatus main body 10,
The photoconductor 12 is rotated, and the image forming process is sequentially performed according to the rotation. In the charging device 13, the charging transformer 51 causes the surface potential to become [V0] suitable for the development of the black toner. Be charged. After this, the photoconductor 12
After passing through the exposure position 14a, development is performed by the first developing device 16a having a black toner, and a toner image by the black toner is formed.

Further, the photosensitive member 12 reaches the transfer peeling charger 17 according to its rotation, and in synchronization therewith, the sheet paper P is fed from any one of the selected paper feed cassettes 21a and 21b. It is sent to the transfer peeling charger 17 through the registration roller pair 26 at the timing when the front end is aligned with the toner image on the photoconductor 12. After transferring the toner image,
The sheet P peeled off from the photoconductor 12 is fixed by the fixing roller pair 28, discharged onto the sheet discharge tray 23 by the sheet discharge roller pair 30, and the copying ends.

The copy of the black toner obtained here is used.
The inclination of the central straight line portion of the gradation of the image density is as shown by the dotted line [B] in FIG.

In this way, when the red toner is used for the copy after the necessary copy by the black toner is obtained, the first developing device 16a is provided with the second toner having the red toner at the developing position 16. When a detection device (not shown) recognizes the fact by exchanging it with the developing device 16b and inputs it to the control device 41, the control device 41 controls the charging transformer 51 so as to be suitable for the development by the red toner. Become.

That is, the controller 41 controls the surface potential of the photoreceptor 12 at the time of development with the black toner, which is the standard potential [V0], and the surface stored in the red toner adjustment area 53b of the non-volatile RAM 53. The surface potential [V1 = V0 × α] of the photoconductor at the time of development by the red toner is calculated from the coefficient [α] for adjusting the potential, and the surface potential of the photoconductor 12 by the charging device 13 is [V0 × α]. The charging transformer 51 is controlled so that

Then, in this state, a copy image by the red toner is obtained in the same manner as in the case of the black toner.

At this time, the gradation of the density of the copy image by the red toner is as shown by the solid line [C] in FIG. 3, and the density of the copy image by the black toner is shown by the dotted line [B]. It is supposed to be close to the slope of the straight line part of the gradation.

According to this structure, the surface potential [V0] of the photosensitive member 12 at the time of development with the black toner is adjusted in consideration of both the electrostatic characteristics of the black developer and the charging characteristics of the photosensitive member 12. In the case of a red toner, this [V0] is used as a reference potential, and only by adjusting the reference potential [V0] in accordance with the electrostatic characteristics of the red developer, a floor having a density substantially the same as that of the image obtained by the black toner. The surface potential for obtaining tonality can be easily obtained.

Therefore, in the red toner, the photoconductor 12
Without complicated adjustment considering the charging characteristics of
The surface potential can be easily adjusted only by considering the electrostatic characteristics of the red developer, and the operation of adjusting the surface potential during manufacturing can be reduced.

The present invention is not limited to the above-described embodiment, but may be modified within the scope of the invention. For example, a plurality of developing devices may be provided in the main body of the device without replacement. The type and number of developing devices that can be used are not limited. Even if the number of developing devices increases, any developer is used as a reference, and the surface potential at the time of development with the reference developer is used as the reference potential. This reference potential is the electrostatic characteristics of the developer and the charging characteristics of the photoconductor. On the other hand, for other developers, the reference potential is adjusted according to the coefficient unique to the electrostatic characteristics of each developer to make the copy image density gradation uniform. Will be obtained.

[0031]

As described above, according to the present invention, regardless of the number of developing devices used, the electrostatic characteristics of the developer and the photosensitivity of only the reference potential at the time of development with any reference developer are used. If adjustment is performed in consideration of the charging characteristics of the body, in other developing devices, the reference surface potential is simply adjusted according to the coefficient peculiar to the characteristics of each developer, and the optimum surface potential required during development is obtained. Can be obtained. Therefore, as in the past,
It is not necessary to individually adjust the surface potential for each developer in consideration of the charging characteristics of the photoconductor, and the operability during the adjustment is significantly improved. Further, this makes it possible to use a large number of developers, and the function of the apparatus can be expanded.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a device body of an embodiment of the present invention.

FIG. 2 is a block diagram showing a control device according to an embodiment of the present invention.

FIG. 3 is a graph showing the gradation of the density of the copy image according to the embodiment of the present invention.

FIG. 4 is a graph showing a charge amount with respect to a stirring time of a toner according to the principle of the present invention.

FIG. 5 is a graph showing a difference in gradation of image density due to toner having different principles of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Device main body 12 ... Photoconductor 13 ... Charging device 16a ... 1st developing device 16b ... 2nd developing device 41 ... Control device 53 ... RAM

Claims (2)

[Claims] 1. An apparatus for developing an electrostatic latent image formed on an image bearing member by a plurality of developing devices each containing a developer having a different electrostatic characteristic including a reference developer,
When the surface potential of the image bearing member by the charging means, which is necessary when developing with the reference developer, is used as the reference potential and the development is performed with any developer different from the reference developer among the plurality of developers, A surface potential adjusting method characterized in that the reference potential is adjusted according to the electrostatic characteristics of the arbitrary developer. 2. An apparatus main body having an image carrier, a charging unit for charging the image carrier to an arbitrary surface potential, and an electrostatic device including a reference developer, which can be installed at a developing position of the image carrier. During development by a plurality of developing devices that respectively store different developers having different characteristics and selectively develop the electrostatic latent image formed on the image carrier, and a developing device that stores the reference developer , While controlling the charging means so as to set the surface potential of the image bearing member to a reference potential required for development, while storing any developer different from the reference developer among the plurality of developers An image forming apparatus comprising: a control unit that controls the charging unit so as to adjust the reference potential according to the electrostatic characteristic of the arbitrary developer during development by the developing device.