JP2005077543A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can efficiently prevent fluctuation in the image quality of output images, even when consecutive image forming operations are performed. <P>SOLUTION: In outputting the plurality of images by the consecutive image forming operations, marginal timing (A+B) when the image quality of the plurality of images in the consecutive image forming operations fluctuates is predetermined. When the consecutive image forming operations reach the marginal timing (A+B) (S9), consecutive image forming operations are suspended, and the image forming condition is adjusted by an adjustment means (S10). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, such as a copying machine, a printer, a facsimile machine, or a complex machine thereof.

  Conventionally, in an image forming apparatus using an electrophotographic method, image forming conditions on an image carrier such as a photosensitive drum are adjusted at a predetermined timing in order to maintain good image quality in an output image. (For example, refer to Patent Document 1).

Such adjustment control of image forming conditions on the image carrier is called process control, and changes in image quality such as image density and gradation in an output image (an image on a transfer material). It is preventing.
Specifically, fluctuations in image quality in the output image include those associated with environmental changes, those associated with changes over time, and those associated with replacement of units relating to image formation and toner supply.

Typical process controls include the following.
First, a plurality of patch patterns (substantially rectangular patterns of electrostatic latent images) are formed on the image carrier. Then, the latent image potential of each patch pattern is measured by a potential sensor. Further, after developing each patch pattern, the toner adhesion amount (development amount) on the patch pattern is measured with a reflection type optical sensor.
Then, a development potential for obtaining the maximum toner adhesion amount is obtained from the latent image potential detected by the potential sensor and the toner adhesion amount detected by the optical sensor. Then, based on the obtained development potential, the image forming conditions (the charging potential, the write light amount for forming the latent image, the development bias, etc.) are adjusted.

  Such process control is performed when the apparatus is started, after a certain time or after a certain number of images have been formed, and at the end of the image forming operation.

JP-A-6-19261 (page 2-3)

  In the conventional image forming apparatus described above, when a continuous image forming operation (continuous print job) is performed in order to output a plurality of images, the image quality of the image being output may gradually vary. That is, when all the output images by the continuous print job are compared, there is a case where the image quality is not uniform and varies.

Such a problem has become more apparent as the operation time or the number of prints (number of outputs) related to a continuous print job increases.
Furthermore, the timing of image quality variation during a continuous print job varies depending on the usage state (degradation state) of the image forming apparatus. For example, when the sensitivity of the image carrier is deteriorated over time, the generation timing of the image quality fluctuation in the continuous print job is earlier than the initial time when there is no sensitivity deterioration.

  Such a problem cannot be ignored particularly in the case of a color image forming apparatus that requires high image quality in terms of color tone.

  The present invention has been made to solve the above-described problems, and provides an image forming apparatus capable of efficiently preventing fluctuations in image quality in an output image even when continuous image forming operations are performed. It is in.

  An image forming apparatus according to a first aspect of the present invention is an image forming apparatus that outputs a plurality of images by continuous image forming operations, and includes an adjusting unit that adjusts image forming conditions on the image carrier. A predetermined timing when the image quality of the plurality of images fluctuates in the continuous image forming operation is predetermined, and the continuous image forming operation is interrupted when the continuous image forming operation reaches the limit time. The image forming conditions are adjusted by the adjusting means.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the limit time is variably formed according to a use state of the apparatus.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the limit time is determined based on the number of outputs related to the plurality of images. .

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first to third aspects, the limit time is based on an operation time related to the continuous image forming operation. It is determined.

  An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the image forming conditions adjusted by the adjusting means are set on the image carrier. At least one of a charging potential, a latent image formed on the image carrier, and a developing bias in a developing unit facing the image carrier.

  In the present invention, even when continuous image forming operations are performed, when an appropriate limit time at which the image quality fluctuates is assumed in advance and the limit time is reached, the image forming operation is interrupted. Adjustment is in progress. Further, the limit time for adjusting the image forming conditions is configured to be variable according to the use state of the apparatus. Accordingly, it is possible to provide an image forming apparatus that can efficiently prevent fluctuations in image quality in an output image related to continuous operation.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire color image forming apparatus will be described with reference to FIG.
As shown in FIG. 1, in the image forming apparatus, a photosensitive belt 1 as an image carrier is disposed to face the intermediate transfer belt 4.
Here, on the inner periphery of the photosensitive belt 1, a driving roller 1a and two driven rollers 1b and 1c are disposed. The photosensitive belt 1 is stretched and supported by these rollers 1a to 1c. Further, the photosensitive belt 1 is driven in the direction of arrow A in the figure by the driving roller 1a.
Further, on the outer periphery of the photosensitive belt 1, a charging unit 2, a writing unit 3, a magenta developing unit 20M, a cyan developing unit 20C, a yellow developing unit 20Y, a black developing unit 20K, an optical sensor 30, and a cleaning unit 6 are disposed. Has been.

Here, the four developing units 20M, 20C, 20Y, and 20K (developing cartridges) store magenta toner, cyan toner, yellow toner, and black toner, respectively. The four developing units 20M, 20C, 20Y, and 20K are configured to be movable between a developing position and a non-developing position, and sequentially form toner images of the respective colors on the photosensitive belt 1.
Specifically, when a cyan toner image is formed on the photosensitive belt 1, the cyan developing unit 20 </ b> C that stores cyan toner moves to a developing position with respect to the photosensitive belt 1. On the other hand, the other developing units 20M, 20Y, and 20K move to the non-developing positions with respect to the photoreceptor belt 1.

Here, the developing position is a position where the developing rollers 22 of the developing units 20M, 20C, 20Y, and 20K are separated from the photosensitive belt 1 at a minute interval, and a position for developing a latent image on the photosensitive belt 1. It is. The non-development position is a position where the developing roller 22 is retracted from the photosensitive belt 1 with reference to the development position, and is a position where the latent image on the photosensitive belt 1 is not developed.
Then, the toner images of the respective colors formed on the photosensitive belt 1 are sequentially transferred on the intermediate transfer belt 4 in a superimposed manner.

Here, a variable developing bias (developing voltage) is applied to the developing roller 22 of each developing unit 20M, 20C, 20Y, 20K from a power supply unit (not shown).
Further, a variable voltage is applied to the charging unit 2 from a power supply unit (not shown), whereby a variable charging potential is applied to the photosensitive belt 1.
Further, the light amount (write light amount) of the exposure light irradiated from the writing unit 3 toward the photosensitive belt 1 is variably formed, whereby a variable latent image is formed on the photosensitive belt 1.
Furthermore, the optical sensor 30 includes a light emitting element such as an infrared light emitting diode and a light receiving element such as a photodiode that receives diffusely reflected light. Then, at a predetermined timing, toner adhesion amounts in a plurality of patch patterns formed on the photosensitive belt 1 are detected. Then, based on the detection result of the optical sensor 30 (voltage output corresponding to the amount of received light), the image forming conditions on the photosensitive belt 1, that is, the above-described development bias, charging potential, and latent image are optimally adjusted. Be controlled. In the present application, such a series of adjustment control means is collectively referred to as an adjustment means.

On the other hand, on the inner periphery of the intermediate transfer belt 4, a driving roller 4a, two driven rollers 4b and 4c, an intermediate transfer roller 5 and a transfer counter roller 8 are disposed. The intermediate transfer belt 4 is stretched and supported by these rollers 4a to 4c, 5 and 8. Further, the intermediate transfer belt 4 is driven in the direction of arrow B in the figure by the drive roller 4a.
A transfer roller 7 and an intermediate transfer belt cleaning unit 9 are disposed on the outer periphery of the intermediate transfer belt 4.

  Here, the transfer roller 7 and the intermediate transfer belt cleaning unit 9 are configured to be able to contact and separate from the intermediate transfer belt 4. The transfer roller 7 and the intermediate transfer belt cleaning unit 9 are retracted away from the intermediate transfer belt 4 until the desired toner image is completely superimposed on the intermediate transfer belt 4. Then, after the superposition of the toner images on the intermediate transfer belt 4 is completed, the transfer roller 7 and the intermediate transfer belt cleaning unit 9 move to a position where they contact the intermediate transfer belt 4.

In this way, the color toner image on the intermediate transfer belt 4 is transferred to the transfer material P by the transfer roller 7 in contact with the intermediate transfer belt 4.
Further, the untransferred toner remaining on the intermediate transfer belt 4 after the transfer process is collected by the intermediate transfer belt cleaning unit 9 in contact with the intermediate transfer belt 4.

On the other hand, a conveyance roller 14, a registration roller pair 15, a fixing unit 16, a paper discharge roller 17, and the like are disposed in the conveyance path of the transfer material P in the image forming apparatus.
Here, the fixing unit 16 includes a fixing roller 16a as a heating unit and a pressure roller 16b as a pressure unit, and fixes an unfixed toner image on the transfer material P.

The image forming apparatus configured as described above operates as follows during image formation.
Referring to FIG. 1, the photosensitive belt 1 travels in the direction of arrow A in the drawing. First, the surface of the photoreceptor belt 1 is charged at a portion facing the charging unit 2. Next, the surface of the photoreceptor belt 1 reaches a portion facing the writing unit 3. Then, an electrostatic latent image corresponding to image information of a desired color among magenta, cyan, yellow, and black is formed on the photosensitive belt 1 by the exposure light emitted from the writing unit 3.

Thereafter, the surface of the photoreceptor belt 1 reaches a portion facing the developing portion corresponding to a desired color among the four developing portions 20M, 20C, 20Y, and 20K. Then, the corresponding color toner is supplied from the developing unit to the latent image on the photosensitive belt 1. Thus, a one-color toner image is formed on the photoreceptor belt 1.
Thereafter, the surface of the photoreceptor belt 1 reaches a portion facing the intermediate transfer belt 4. The toner image formed on the photosensitive belt 1 is transferred onto the intermediate transfer belt 4 by the intermediate transfer roller 5 to which a predetermined voltage is applied.

Here, untransferred toner that has not been transferred to the intermediate transfer belt 4 remains on the photosensitive belt 1 after passing through the portion facing the intermediate transfer belt 4.
Then, the surface of the photoreceptor belt 1 to which the untransferred toner is attached reaches a portion facing the cleaning unit 6. At this position, the untransferred toner is collected in the cleaning unit 6. The toner collected in the cleaning unit 6 is then transported toward the round storage unit 11.

Such a series of processes on the photosensitive belt 1 is similarly performed for the other colors. The toner images formed on the photosensitive belt 1 by sequentially moving the four developing units 20M, 20C, 20Y, and 20K are transferred onto the intermediate transfer belt 4 in an overlapping manner.
Note that the operation of exchanging the four developing units 20M, 20C, 20Y, and 20K and the image forming process such as the charging process, the writing process, the transfer process, and the cleaning process are continuously performed. That is, the charging process and the writing process are performed during the movement of the developing unit to the developing position, and the developing process is performed as soon as the movement of the developing unit is completed. When the developing process is completed, the developing unit is moved to the non-developing position and the next developing unit is moved to the developing position, and an image forming process such as a transfer process and a cleaning process is performed in the meantime. Thus, a series of image forming processes is efficiently performed in a short time.

Thereafter, the color toner image formed over the intermediate transfer belt 4 reaches the portion facing the transfer roller 7 as the intermediate transfer belt 4 travels in the arrow B direction. At this position, the toner image is transferred onto the transferred material P that has been conveyed.
Here, untransferred toner that has not been transferred to the transfer material P remains on the intermediate transfer belt 4 after passing through the portion facing the transfer roller 7.
Then, the surface of the intermediate transfer belt 4 to which the untransferred toner adheres reaches a portion facing the intermediate transfer belt cleaning unit 9. At this position, the untransferred toner is collected in the intermediate transfer belt cleaning unit 9. The toner collected in the intermediate transfer belt cleaning unit 9 is then transported toward the storage unit 12.
Thus, a series of processes on the intermediate transfer belt 4 is completed.

On the other hand, the transfer material P fed from the paper feed unit 13 reaches the position of the registration roller pair 15 after passing through the transport roller 14. The transfer material P that has reached the position of the registration roller pair 15 is conveyed toward the position of the transfer roller 7 in time so that the toner image formed on the intermediate transfer belt 4 is transferred.
Thereafter, the transfer material P that has passed the position of the transfer roller 7 reaches the position of the fixing unit 16. At this position, the toner image on the transfer material P is fixed.
Then, the transfer material P as an output image passes through the fixing unit 16 and is then discharged out of the image forming apparatus via the paper discharge roller 17.
Thus, a series of image forming operations in the image forming apparatus is completed.
Note that in the case of a continuous print job (a job for continuously outputting a plurality of images with a single print command by the user), the above-described image forming operation is performed continuously.

Next, image forming condition adjustment control (process control) by the adjusting means in the above-described image forming apparatus will be described.
First, a plurality of patch patterns are formed on the photosensitive belt 1. Then, the latent image potential of each patch pattern is measured by a potential sensor (not shown). Further, after each patch pattern is developed, the toner adhesion amount on the patch pattern is measured by the optical sensor 30. Here, the patch pattern is formed based on the image forming process described above.
Then, a development potential for obtaining the maximum toner adhesion amount is obtained from the latent image potential detected by the potential sensor and the toner adhesion amount detected by the optical sensor 30. Based on the obtained development potential, the charging potential, the write light quantity, and the development bias are adjusted.

Next, control in the image forming apparatus of the present embodiment will be described with reference to FIGS.
The image forming condition adjustment control described above is mainly performed when an image forming operation is not performed, such as when the apparatus is started immediately after the main power is turned on, or when the apparatus is stopped between print jobs. It is. However, in the present embodiment, adjustment control of image forming conditions is performed as necessary even during a continuous print job.

As shown in FIG. 2, first, when there is a print command from the user (step S1), the counter n relating to the number of prints is counted up by one (step S2).
Then, it is determined whether the counter n is larger than a set value A (for example, 200) (step S3). As a result, when it is determined that the counter n is smaller than the set value A, it is further determined whether or not the print command is completed (step S4).

As a result, if it is determined that the print command is finished, that is, if the print command is a print command, this control is finished (step S5).
On the other hand, if it is determined that the print command is not completed, that is, if it is a command related to continuous printing with a plurality of prints, the control from step S2 is repeated.

If it is determined in step S3 that the counter n is greater than or equal to the set value A, it is further determined whether or not the print command is complete (step S6).
As a result, if it is determined that the print command is completed, the image forming condition adjustment control (number control) described with reference to FIG. 1 is performed (step S7), and this control is terminated (step S8). ).

  On the other hand, if it is determined in step S6 that the print command is not completed, it is further determined whether the counter n has reached the limit number (A + B) (step S9). Here, the limit number (A + B) is a limit time (strictly, a margin is included) at which the image quality of an output image related to a continuous print job is expected to deteriorate, and is based on the number of prints. It is determined. For example, B is set to 500.

As a result, if it is determined that the counter n is equal to or greater than the limit number (A + B), the continuous print job is interrupted, and the image forming condition adjustment control (number control) described with reference to FIG. 1 is performed. Implemented (step S10). Then, control after step S2 is performed.
Further, also when it is determined in step S9 that the counter n is smaller than the limit number (A + B), the control after step S2 is performed.

As described above, in this embodiment, when the number of prints related to a continuous print job reaches the limit number (A + B), the continuous print job is interrupted to perform process control, and then the continuous print job is performed. To resume. Here, the limit number (A + B) is set in advance based on various experimental data and simulation results in order to prevent quality degradation of the output image when continuous printing is continued. As a result, the quality of the output image related to the continuous print job is uniform and has little variation.
In the present embodiment, the limit time at which image quality fluctuations occur is determined by the number of printed sheets (count n), but the operation time related to the print job (for example, the rotation time of the photosensitive belt 1). It can also be determined on the basis.

Next, another control shown in FIG. 3 will be described.
In the control according to the present embodiment, the limit number (A + B) described in FIG. 2 is variably formed according to the use state of the apparatus. Specifically, the set value B (interval B) in FIG. 2 is varied based on the flow in FIG.

  As shown in FIG. 3, first, it is determined whether the developing unit counters of the developing units 20M, 20C, 20Y, and 20K are larger than a predetermined value (steps S15 to S16). Here, the development counter is a counter for each developing unit in which the actual number of printed sheets is converted into the number of printed A4 size transfer materials P, and correlates with the usage state (degraded state) of each developing unit. is there. That is, the larger the development counter, the greater the mechanical consumption of the developing section. The predetermined value of the development counter is set to 20000, for example.

If it is determined in step S16 that the development counter is greater than the predetermined value (20000), the setting value B in FIG. 2 is set to 200 (step S17), and this control is terminated (step S20). ). Here, the default value of the setting value B is 500. In other words, when the degree of deterioration of the developing unit advances, the limit number (A + B) related to interruption of the continuous print job is controlled to be small.
In the present embodiment, this control flow is executed when even one of the four developing counters related to the four developing units 20M, 20C, 20Y, and 20K reaches a predetermined value.

  If it is determined in step S16 that the development counter is equal to or smaller than the predetermined value (20000), it is further determined whether the photoconductor counter is larger than the predetermined value (step S18). Here, the photoconductor counter is a counter of the photoconductor belt 1 in which the actual number of prints is converted into the number of printed A4 size transfer materials P, and is correlated with the use state (deterioration state) of the photoconductor belt 1. To do. That is, the larger the photoreceptor counter, the greater the mechanical wear of the photoreceptor belt 1. The predetermined value of the photoconductor counter is set to 50000, for example.

As a result, when it is determined that the photoconductor counter is larger than the predetermined value (50000), the set value B is set to 200 because the photoconductor belt 1 has an influence on the image quality fluctuation and is set to be 200 (step). S17), this control is finished (step S20).
On the other hand, when it is determined that the photoconductor counter is equal to or less than the predetermined value (50000), it is assumed that there is no deterioration of the photoconductor belt 1 and the developing units 20M, 20C, 20Y, and 20K. Is set to 500 (default value) (step S19).
Thus, this control is finished (step S20).

  As described above, in this embodiment, control is performed so as to change the limit number (A + B) related to interruption of continuous print jobs in accordance with the deterioration state of the image forming apparatus. As a result, the quality of the output image related to the continuous print job can be made efficient, uniform and less varied depending on the situation.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is obvious that the embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the embodiment. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention.

1 is a configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 3 is a flowchart illustrating control in the image forming apparatus in FIG. 1. 6 is a flowchart showing another control in the image forming apparatus of FIG. 1.

Explanation of symbols

1 photosensitive belt (image carrier), 2 charging unit, 3 writing unit,
4 intermediate transfer belt, 6 cleaning section, 7 transfer roller,
13 paper feed unit, 14 transport roller, 15 registration roller pair,
16 fixing section, 17 paper discharge roller,
20K, 20Y, 20C, 20M Development section, 30 Optical sensor.

Claims (5)

An image forming apparatus that outputs a plurality of images by a continuous image forming operation,
An adjusting means for adjusting image forming conditions on the image carrier;
A limit time at which image quality of the plurality of images fluctuates in the continuous image forming operation is determined in advance, and when the continuous image forming operation reaches the limit time, the continuous image forming operation is interrupted and the adjustment is performed. An image forming apparatus, wherein image forming conditions are adjusted by means. The image forming apparatus according to claim 1, wherein the limit time is variably formed according to a use state of the apparatus. The image forming apparatus according to claim 1, wherein the limit time is determined based on the number of outputs related to the plurality of images. 4. The image forming apparatus according to claim 1, wherein the limit time is determined based on an operation time related to the continuous image forming operation. The image forming condition adjusted by the adjusting means is at least one of a charging potential on the image carrier, a latent image formed on the image carrier, and a developing bias in a developing unit facing the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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