JP2000066552A - Image forming device, and image forming process adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a tower pattern for adjusting an image forming process to be recovered on an image carrier without separating an intermediate transfer body from the image carrier. SOLUTION: In the image forming device, in addition to an image forming operation of transferring the toner image on the image carrier 1 on to the intermediate transfer body 6 by the transfer bias of transfer means 6a and 6b, the image forming process adjusting operation is executed by forming the toner pattern on the image carrier 1. In this case, each transfer bias of the transfer means 6a and 6b is switched to 0 V so as not to transfer the toner pattern to the intermediate transfer body, besides, in the case of reducing the discharging power of a pre-cleaning discharging means 7 with a prescribed timing difference from the time when the transfer bias comes to 0 V, the synergetic effects such as the stabilization of the cleaning performance and the energy saving, etc., are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, etc., and more particularly, to a color image forming apparatus having an image bearing member and an intermediate transfer member. The present invention relates to a technique for processing a toner pattern formed during a process adjustment operation.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an electrostatic latent image of each color is formed on the surface of a rotating image carrier, and each electrostatic latent image is developed with a corresponding color toner. A color image in which a full-color image is obtained by transferring a toner image onto an intermediate transfer body that rotates in contact with the image carrier so as to be sequentially overlapped, and collectively transferring the overlap-transferred image from the intermediate transfer body to transfer paper. Forming devices are known.

In many cases, in such a color image forming apparatus, in addition to the above-described image forming operation, an image forming apparatus capable of adjusting a process condition at the time of image forming in response to aging deterioration of an image carrier, environmental change, and the like. A process adjustment operation is being performed. This image forming process adjustment operation forms a toner pattern of each color gradation on the image carrier, detects the photoconductor potential and toner density, and based on the detection results, the charging grid and the developing bias of the image carrier. This is potential control for adjusting process conditions such as the above. The image forming process adjusting operation is performed, for example, immediately after the main power is turned on or at the end of every 150 jobs.

Conventionally, the toner pattern formed on the image carrier by the above-described image forming process adjustment operation does not need to be transferred to a transfer sheet, and has been removed and recovered by one of the following two methods. . In the first method, after a toner pattern formed on an image carrier is transferred onto an intermediate transfer member, the toner pattern is removed and collected by a belt cleaning device that cleans the intermediate transfer member. This method is employed in an apparatus in which the image carrier and the intermediate transfer body are always in contact. Since there is a cleaning device for the image carrier on the downstream side of the transfer unit, the toner pattern is transferred to the intermediate transfer body due to its configuration. Therefore, the toner pattern is removed and collected from the intermediate transfer body. In a second method, the image forming process adjusting operation is performed in a state where the image carrier and the intermediate transfer member are separated from each other,
The toner pattern is removed and collected by the image carrier cleaning device without transferring the toner pattern to the intermediate transfer member. This method is employed in an apparatus provided with a holding mechanism capable of bringing an intermediate transfer member into and out of contact with an image carrier.

[0005]

However, when the above-described first method is employed, the amount of toner collected by the belt cleaning device for the intermediate transfer member increases each time the image forming process adjustment operation is performed. In addition, the belt cleaning device performs an operation of bringing the cleaning member into and out of contact with the intermediate transfer body. For example, when a four-color superimposed transfer image is formed, the cleaning member is separated from the belt surface of the intermediate transfer body at the time of transfer of the first to third colors, and the cleaning member is brought into contact after batch transfer of the superimposed transfer image. Needs cleaning. For this reason, there is a problem that the toner is scattered during the contact / separation operation as a result of an increase in the amount of collected toner.

On the other hand, the second method can be adopted in an apparatus having a mechanism for contacting and separating an intermediate transfer member. However, the provision of such a contact / separation mechanism not only complicates the configuration and increases the number of components, but also requires a higher precision in the tolerance of components related to the transfer position accuracy for accurately overlapping the toner image at the same position. Is done. That is, in the image forming apparatus, the provision of the contact / separation mechanism for the intermediate transfer member is not originally preferable.

Therefore, an apparatus has been developed which allows the toner pattern to reach the cleaning device on the image carrier without being transferred to the intermediate transfer body, and which can be removed and recovered from the image carrier irrespective of the mechanism for contacting and separating the intermediate transfer body. There is a need to.

Accordingly, an object of the present invention is to remove and collect a toner pattern formed for adjusting an image forming process with a cleaning device for an image carrier without separating the intermediate transfer member from the image carrier, and to perform belt cleaning. An object of the present invention is to provide an image forming apparatus and an image forming process adjusting method capable of preventing toner scattering from the apparatus.

[0009]

An image forming apparatus according to the present invention for achieving the above object forms an electrostatic latent image on the surface of a rotating image carrier, develops the electrostatic latent image into a toner image, An image forming operation for transferring the toner image on the image carrier to the intermediate transfer body is possible by a transfer unit that applies a transfer bias to a transfer portion formed between the image carrier and the intermediate transfer body. An image forming apparatus in which, before an image forming operation, an image forming process adjusting operation of forming a toner pattern of each color gradation on the image carrier and adjusting a process condition at the time of image forming based on detection of the toner pattern is performed. Wherein the transfer means makes the transfer bias variable so as not to transfer the toner pattern to the intermediate transfer member during the image forming process adjustment operation.

According to the image forming process adjusting method of the present invention which achieves the above object, an electrostatic latent image is formed on the surface of a rotating image carrier, the electrostatic latent image is developed into a toner image, and the toner image is developed. In addition to the image forming operation in which a transfer bias is applied and the image is transferred onto the intermediate transfer member, a toner pattern of each color gradation is formed on the image carrier, and the process conditions during image formation are determined based on the detection of the toner pattern and the like. In the adjusting method for adjusting an image forming process, the transfer bias is switched so that the toner pattern is not transferred to the intermediate transfer member. In this case, the transfer bias of the transfer unit is set to 0.
Switch to bolts.

The pre-cleaning charge removing means provided in the circumferential direction of the image carrier and downstream of the transfer bias application position removes the charge on the area on the image carrier where the transfer bias is switched. It is preferable to make the potential of the image carrier after the switching and the charge elimination uniform.

In this case, it is preferable that the static elimination by the pre-cleaning static elimination means is performed at a predetermined timing difference from the switching of the transfer bias. For example, the length on the circumference of the image carrier from the application position of the transfer bias to the position of the pre-cleaning static elimination means is L, the peripheral speed of the image carrier is W, and the predetermined timing difference is T. Then, the relationship of T = L / W can be satisfied.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of the image forming apparatus of the present embodiment. The image carrier composed of the drum-shaped photoconductor 1 is supported rotatably in the counterclockwise direction. Around the photoconductor 1, a main charger 2, a potential sensor 19,
The developing unit 4, the density detection sensor 20, the intermediate transfer body 6, the pre-cleaning neutralizing unit 7, the photoconductor cleaning device 8, and the neutralizing lamp 9 are provided.

The photoreceptor 1 is rotated at a predetermined peripheral speed W, and the surface thereof is uniformly negatively charged by the main charger 2. The surface of the photoconductor 1 is irradiated with each color separation light 3 corresponding to the intensity level of each color separation image signal from a document reading device and an optical writing unit (not shown). Then, on the surface, an electrostatic latent image is formed due to an increase in the potential of the irradiated portion (the absolute value of the potential decreases toward the plus side). When the electrostatic latent image formed for each color reaches the developing unit 4, it is developed by a predetermined developing device. In this developing step, a developing bias is applied to the developing roller 4a of the developing device, and the toner negatively charged due to friction in the developing device is transferred to the photosensitive member 1.
To the portion where the potential rises.

The intermediate transfer member 6 includes bias rollers 6a and 6
b, a driving roller 6c, a cleaning opposing roller 6d, a transfer belt 6e, and the like. The transfer belt 6e is stretched by the bias roller 6a and the bias roller 6b so as to come into contact with the surface of the photoconductor 1, thereby forming a primary transfer portion. And the driving roller 6c
Is driven by a drive motor (not shown), the transfer belt 6 e rotates clockwise at the same peripheral speed as the photosensitive member 1.
In the intermediate transfer body 6 of the present embodiment, a contact / separation mechanism for separating the transfer belt 6e from the photoconductor 1 is not provided,
The next transfer portion is in a contact state.

The bias roller 6a is connected to a power source, and the bias roller 6b is grounded. When a predetermined voltage is applied to the bias roller 6a, a positive primary transfer bias is generated on the transfer belt 6e between the bias roller 6a and the bias roller 6b, and the negatively charged toner on the photoconductor 1 is charged. Is transferred onto the intermediate transfer member 6. The primary transfer process is sequentially performed so as to overlap the same position on the intermediate transfer body 6 for each color. For example, in a four-color full-color mode, a four-color superimposed toner image is formed.

The superimposed transfer image formed on the intermediate transfer member 6 is collectively transferred onto a transfer sheet 11 sent from a sheet supply unit 10. In the secondary transfer step, the secondary transfer member 12 is moved from the virtual line position to the solid line position in FIG. Then, a secondary transfer bias is applied to the secondary transfer member 12 to transfer the toner image. Thereafter, when the transfer paper 11 is sent to the fixing device 14 by the transport device 13, the transfer paper 11 is heated and pressed to fix the toner, and is discharged to the paper discharge unit 15.

The belt cleaning device 16 has a cleaning member 17 and an entrance seal member 18, and the cleaning member 17 cleans the surface of the intermediate transfer member 6. The belt cleaning device 16 is provided with a contact / separation mechanism for bringing the cleaning member 17 into and out of contact with the transfer belt 6e. The contact / separation mechanism is controlled at a predetermined timing from the start of the secondary transfer process so that the cleaning member 17 contacts the surface of the transfer belt 6e after the secondary transfer. Then, the transfer residual toner that has not been transferred to the transfer paper 11 in the secondary transfer step is scraped off by the cleaning member 17 and collected in the belt cleaning device 16.

The pre-cleaning charge removing means 7 is arranged downstream of the primary transfer portion, that is, downstream of the bias roller 6a by a length L on the circumference of the photosensitive member 1. The surface potential of the photoreceptor 1 that has passed through the primary transfer section has changed to the positive side due to the transfer bias in the primary transfer step. Therefore, the pre-cleaning charge removing means 7 returns the surface of the photoconductor 1 to a normal potential level (minus side) by applying an AC current. Thus, the photoconductor 1
By returning the potential level from the positive side to the negative side,
The cleaning performance of the photoconductor cleaning device 8 is improved.

After cleaning by the photoreceptor cleaning device 8, the surface of the photoreceptor 1 is erased of residual charges by a neutralization lamp 9. Here, if continuous copying is performed, the surface of the photoreceptor 1 is charged again by the main charger 2 and the next charging is performed. The process proceeds to the image forming process.

Next, the image forming process adjusting operation of the image forming apparatus according to the present embodiment will be described. The image forming process adjusting operation of the present embodiment detects the image forming state of the photoconductor 1, calculates a developing potential (developing ability to attach toner), and sets the image forming condition based on the calculated potential. Specifically, it is performed by potential control described below. FIG.
9 is a chart showing an outline of an image forming process adjusting operation of the present embodiment. First, a pattern of a plurality of electrostatic latent images having different color gradations for each color is sequentially formed on the photoconductor 1 (S
1). Each pattern is detected by the potential sensor 19, and the potential on the surface of the photoconductor 1 is measured (S2).

Each electrostatic latent image pattern is developed into a toner pattern by a developing unit, and each toner pattern is detected by the density detection sensor 20 (S3). At this time, the output value of the density detection sensor is converted into the amount of toner adhered on the photoconductor 1.

The controller of the image forming apparatus linearly approximates the potential of the photosensitive member 1 measured by the potential sensor 19 and the amount of toner detected by the density detecting sensor 20 to calculate the developing potential of the photosensitive member 1. (S4).

Next, selection and determination of image forming conditions are performed based on the development potential (S5). Selectable image forming conditions are set in advance in about 20 combinations of the charging grid of the photoconductor 1, the photoconductor potential, and the developing bias. Here, if the calculated developing potential is determined and image forming conditions corresponding to the aging of the photoconductor 1 and environmental changes are determined, the developing potential necessary for subsequent image formation can be secured.

The image forming apparatus according to the present invention removes each toner pattern used in the image forming process adjusting operation by the photosensitive member cleaning device 8 without transferring the toner pattern to the intermediate transfer member 6. For this reason, the primary transfer means including the bias rollers 6a and 6b has a configuration in which the transfer bias is variable, and is controlled so as not to apply the transfer bias to the toner pattern passing through the primary transfer portion. .

In this embodiment, before the leading end of the toner pattern reaches the primary transfer portion, the voltage applied to the bias roller 6a is switched to 0 volt (S6). Applied voltage is 0
If V, no transfer bias is generated, and the toner pattern is not transferred onto the intermediate transfer member 6 even when the photosensitive member 1 and the intermediate transfer member 6 are kept in contact with each other. At the same time as the trailing end of the toner pattern leaves the primary transfer portion, the applied voltage is switched so that the transfer bias is returned to a predetermined voltage again (S7). Note that switching of the applied voltage is not limited to switching to 0 volt. For example, a polarity opposite to the transfer bias, that is, a negative bias may be applied.

As a result of switching the applied voltage to 0 volts, the surface potential of the photosensitive member 1 to which no positive transfer bias is applied does not change to the positive side unlike the normal image forming operation. That is, since the surface potential of the photoconductor 1 in that region remains on the negative side, in the present embodiment, the power removal of the pre-cleaning charge removing unit 7 is controlled to be smaller than that in the normal operation.

More specifically, the current value is lowered at the same time when the leading end of the area where the transfer bias is not applied reaches the pre-cleaning charge removing means 7 (S9). At the same time as the rear end of the region passes, the current value is increased and the power removal is returned to the original (S10). In this way, even when the transfer bias is switched, the potential level at the time of arrival of the photoconductor cleaning device 8 can be maintained at the same level as during the normal image forming operation. Problems such as changing the ability can be prevented. Further, lowering the applied current value of the pre-cleaning static elimination means 7 has the effect of suppressing the generation of ozone due to discharge and of saving energy.

As shown in the chart of FIG. 2, the switching of the applied current is preferably performed at the timing of the time difference T from the switching of the transfer bias. Time difference T
Is a pre-cleaning static elimination means 7 from the bias roller 6a.
From the length L of the photoconductor 1 on the circumference of the photoconductor 1 and the rotation speed W of the photoconductor 1, a relational expression of T = L / W is given. In this way, the charge removal according to the potential level of the photoconductor 1 can be efficiently performed without waste. Then, each of the removed toner patterns is removed and collected by the photoconductor cleaning device 8 (S8).

[0030]

As described above, in the present invention, the transfer bias is switched so that the toner pattern formed on the image carrier is not transferred to the intermediate transfer member during the adjustment of the image forming process. The toner pattern can be removed and collected by the image carrier cleaning device without separating the toner pattern from the photoconductor.

In addition, the pre-cleaning static elimination means provided in the circumferential direction of the image carrier downstream of the transfer bias application position removes the static electricity from the area on the image carrier to which the transfer bias has been switched. If the potential of the image carrier after switching and static elimination is made uniform, the potential level of the surface of the image carrier that reaches the cleaning device of the image carrier during the image forming process adjustment operation is the same as the potential level during the normal image forming operation. The cleaning performance can be stabilized, and the generation of ozone can be suppressed.

At this time, if the static elimination by the pre-cleaning static elimination means is performed at a predetermined timing difference from the switching of the transfer bias, the effect of stabilizing the cleaning performance and the like can be efficiently obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a chart illustrating an image forming process adjusting method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 6 Intermediate transfer body 6a, 6b Transfer means (primary transfer means) 7 Static electricity removal means before cleaning

Claims (6)

[Claims] 1. An image forming apparatus comprising: an electrostatic latent image formed on a surface of a rotating image carrier; developing the electrostatic latent image into a toner image; The image forming operation of transferring the toner image on the image carrier onto the intermediate transfer member can be performed by a transfer unit that applies a transfer bias to the image carrier. An image forming apparatus in which an image forming process adjusting operation for forming a toner pattern and adjusting a process condition at the time of image forming based on the detection of the toner pattern is performed. An image forming apparatus wherein the transfer bias is variable so that a toner pattern is not transferred to an intermediate transfer member. 2. An electrostatic latent image is formed on the surface of a rotating image carrier, the electrostatic latent image is developed into a toner image, and a transfer bias is applied to the toner image to transfer the toner image onto an intermediate transfer member. In an image forming process adjusting method for forming a toner pattern of each color gradation on the image carrier and adjusting a process condition at the time of image formation based on detection of the toner pattern, other than during the image forming operation, An image forming process adjusting method, wherein the transfer bias is switched so as not to transfer to an intermediate transfer member. 3. The method according to claim 2, wherein the transfer bias is switched to 0 volt. 4. A pre-cleaning static elimination means provided in a circumferential direction of the image carrier and downstream of an application position of the transfer bias to remove electricity from an area on the image carrier to which the transfer bias is switched. 4. The image forming process adjusting method according to claim 2, wherein the potential of the image carrier after switching and charge elimination is made uniform. 5. The image forming process adjusting method according to claim 4, wherein the static elimination by the pre-cleaning static elimination means is performed at a predetermined timing difference from the switching of the transfer bias. 6. A method according to claim 1, wherein a length on the circumference of the image carrier from the application position of the transfer bias to the position of the pre-cleaning charge removing unit is L, a peripheral speed of the image carrier is W, 6. The image forming process adjustment method according to claim 5, wherein when T is T, the relationship of T = L / W is satisfied.