JP5267120B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that performs control to remove deposits on the surface of an image bearing rotator such as a photosensitive drum, and more particularly to a technique for improving the life of an image bearing rotator.

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic printer, there is a scorotron type charger that charges a surface of an image bearing rotating body such as a photosensitive drum by corona discharge.
In this charger, a large amount of ozone is generated during corona discharge, so that components in the air are oxidized.

As a result, discharge products such as nitrogen oxides are generated in the air, but these discharge products eventually adhere to the surface of the image bearing rotating body while drifting in the air. It becomes a factor which degrades.
More specifically, when the discharge product adheres to the surface of the image bearing rotating body, the charging characteristic is reduced only at that portion, and the toner adhesion amount is reduced, so that white streaks appear on the printed first page or the like. The phenomenon that occurs.

  Therefore, in the conventional image forming apparatus, for example, when the power is turned on or when the door of the housing that has been opened after closing the jam is closed, the fixing device is preheated in parallel with the so-called warm-up operation. Each time, so-called idling is performed to rotate the image bearing rotator irrespective of the image forming operation, and the discharge product is removed by a cleaning member in contact with the surface of the image bearing rotator (for example, Patent Document 1).

In addition, the image forming apparatus disclosed in Patent Document 2 performs idling every time in parallel with the warm-up operation, as well as Patent Document 1, and in addition, the image forming operation is not performed for a long time. If left unattended for a long time, depending on the length of the unattended time, the idle rotation time may be longer than usual, or the rotation speed of the image bearing rotating body may be increased even if the idle rotation time is the same. Thus, the discharge product is more reliably removed from the surface of the image bearing rotating body.
JP-A-6-149129 Japanese Patent Laid-Open No. 7-121077

However, since the surface of the image bearing rotator is somewhat scraped by performing the idling of the image bearing rotator as described above, the image bearing rotator is deteriorated and its life is shortened. There is.
The present invention has been made in view of the above-described problems, and shortens the life of the image bearing rotator more than necessary while preventing deterioration of image quality due to adhesion of discharge products to the surface of the image bearing rotator. An object of the present invention is to provide an image forming apparatus that does not occur.

In order to achieve the above object, the image forming apparatus according to the present embodiment is an image forming apparatus that charges a rotating image carrier rotating body to form a toner image on the peripheral surface of the charged image bearing rotating body. A cleaning member that comes into contact with the peripheral surface of the image bearing rotator and removes deposits on the peripheral surface, a warm-up determining means that determines execution of a warm-up operation, A first index value acquisition unit that acquires a stop time index value that indicates a stop time until the current state is maintained, a humidity index value that indicates humidity in the apparatus, and the current image bearing rotating body When the second index value acquisition means for acquiring at least one index value of the deterioration degree index values indicating the degree of deterioration and execution of the warm-up operation are determined, Based on the stop time index value acquired by the index value acquisition means and the at least one index value acquired by the second index value acquisition means, the execution time for executing the idling of the image bearing rotating body If the determined execution time is not 0, the idle rotation of the image bearing rotator is executed for the execution time in parallel with the warm-up, and the determined execution time is 0 Includes a control means for controlling so as not to execute the idling, a memory storing the stop time when the image carrying rotator has changed from a rotation state to a stop state, a clock for outputting the current time, Transfer means for transferring the toner image carried on the image carrying rotator to the sheet, and a fixing unit for fixing the toner image on the sheet by heating and pressurizing the sheet on which the toner image is transferred. , And a temperature detecting means for detecting the temperature of the fixing unit, the second index value acquisition means has acquired the humidity indicator value and deterioration degree index value, the control means, the stop time index value The humidity index value and the deterioration degree index value and the corresponding threshold values are respectively compared to perform case division, and a time associated with each case in advance is selected as the idle rotation execution time. When the execution of the warm-up operation is determined and the current time can be acquired, the time from the stop time to the current time is derived as the stop time index value, and the current time cannot be acquired Is characterized in that the stop time index value is estimated based on the temperature of the fixing unit .

  In the above configuration, the idle running time is determined based on the stop time index value and at least one of the humidity index value and the deterioration degree index value. The amount of attachment of the kimono can be predicted with higher accuracy, and the life of the image bearing rotator can be unduly shortened by performing idling even though no deposit is adhered to the image bearing rotator. Disappears.

Furthermore, since the idle running time is determined based on the three index values of the stop time index value, the humidity index value, and the deterioration degree index value, the amount of adhesion can be estimated with high accuracy.

In addition, even when the current time cannot be acquired at the timing of executing the warm-up, the stop time index value can be estimated based on the temperature of the fixing unit, so the idling can be performed without delaying the warm-up timing. Can be executed.
According to another aspect of the present invention, the image forming apparatus includes a plurality of image carrying rotators and one drive unit that rotationally drives each image carrying rotator, and the second index value obtaining unit is provided for each image carrying rotator. The deterioration degree index value is acquired for each of the image bearing rotators, and the control unit is configured to determine whether or not all the image bearing rotators are empty based on the largest degradation degree index value among the deterioration degree index values acquired for each image bearing rotator. You may determine the execution time of rotation.

In the above configuration, the execution time of idling is determined based on the degradation degree index value having the largest value among the degradation degree index values acquired for each image bearing rotating body, and the idling speed is determined based on the safest side. The execution time can be determined, and so-called white streak is unlikely to occur even if a plurality of image bearing rotators include those that have not been exchanged for a long time.
Furthermore, it is preferable that the control means determines the time for performing the idling so that the idling is completed when the warm-up operation is completed.

  Thus, the waiting time until image formation is started does not become longer than necessary.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described by taking as an example a case where it is applied to a tandem color digital printer (hereinafter simply referred to as “printer”).
FIG. 1 is a schematic cross-sectional view showing the overall configuration of the printer 1.
As shown in the figure, the printer 1 includes an image processing unit 3, a paper feeding unit 4, a fixing unit 5, and a control unit 60. The printer 1 is connected to a network (for example, a LAN) and is connected to an external terminal device (not connected). When a print job execution instruction is received from the figure, a toner image of each color of yellow, magenta, cyan, and black is formed based on the instruction, and a full color image formation is executed by multiple transfer of these toner images.

Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.
<Image process part>
The image processing unit 3 includes image forming units 3Y, 3M, 3C, and 3K, an optical unit 10, an intermediate transfer belt 11, and the like.

  The image forming unit 3Y abuts the surface of the photosensitive drum 31Y and the charger 32Y, the developing unit 33Y, the primary transfer roller 34Y, and the surface of the photosensitive drum 31Y disposed around the photosensitive drum 31Y, and removes deposits on the surface. A plate-like cleaning member 35Y to be removed is provided, and a Y-color toner image is formed on the photosensitive drum 31Y. The other image forming units 3M to 3K also have the configuration of the chargers 32M to 32K as in the image forming unit 3Y except that the color of the toner is different. However, in order to prevent the drawings from becoming complicated, The sign of is not shown.

Each of the photosensitive drums 31Y to 31K can be individually replaced, and is configured to be rotationally driven all at once by the same drive source (not shown).
Each of the chargers 32Y to 32K is a scorotron charger, and generates a high potential difference between a pair of electrodes facing each other across a space to cause corona discharge, thereby causing the surface of the photoreceptor to have a predetermined potential due to its electrical action. To be charged.

The intermediate transfer belt 11 is an endless belt, is stretched around a driving roller 12 and a driven roller 13, and is driven to rotate in the direction of arrow A.
The optical unit 10 includes a light emitting element such as a laser diode. The optical unit 10 emits laser light L for forming images of Y to K colors according to a drive signal from the control unit 60, and exposes and scans the photosensitive drums 31Y to 31K.

By this exposure scanning, electrostatic latent images are formed on the photosensitive drums 31Y to 31K charged by the chargers 32Y to 32K.
The electrostatic latent images are developed by the developing devices 33Y to 33K, and Y to K color toner images are developed on the photosensitive drums 31Y to 31K, whereby Y, M are respectively formed on the photosensitive drums 31Y to 31K. A toner image as a C, K developer image is formed.

The image forming operations for the respective colors are executed at different timings so that the primary transfer is performed while being superimposed on the same position on the intermediate transfer belt 11.
The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 11 by the electrostatic force acting by the primary transfer rollers 34Y to 34K to form a full-color toner image, and further move toward the secondary transfer position 46.

An in-machine temperature sensor 69 and an in-machine humidity sensor 70 for detecting relative humidity are provided around the secondary transfer position 46.
On the other hand, the paper feed unit 4 includes a paper feed cassette 41 that accommodates the paper S, a feed roller 42 that feeds the paper S in the paper feed cassette 41 one by one onto the transport path 43, and a secondary feed of the fed paper S. A timing roller pair 44 and the like are provided for timing to send the toner to the transfer position 46, and the paper S is fed from the paper supply unit 4 to the secondary transfer position in accordance with the movement timing of the toner image on the intermediate transfer belt 11. The toner images on the intermediate transfer belt 11 are secondarily transferred onto the sheet S all at once by the action of electrostatic force by the secondary transfer roller 45.

The sheet S that has passed the secondary transfer position 46 is further conveyed to the fixing unit 5, and the toner image (unfixed image) on the sheet S is fixed on the sheet S by heating and pressurization in the fixing unit 5. The paper is discharged onto a discharge tray 72 via a discharge roller pair 71.
The fixing unit 5 includes a fixing roller 51 having a heat generating layer provided on the surface thereof, an induction coil 52 that induction-heats the fixing roller 51, a pressure roller 53 that pressurizes the fixing roller 51, and a temperature sensor that detects the temperature of the fixing roller 51. 54 or the like.
<Control unit>
FIG. 2 is a block diagram illustrating a configuration of the control unit 60 of the printer 1.

As shown in the figure, the control unit 60 includes a printer controller CPU 61, an engine CPU 62, a clock 61a, an interface (I / F) unit 63, a RAM 64, a ROM 65, an HDD 66, an EEPROM 68a, a ROM 68b, and a RAM 68c as main components. ing.
The printer controller CPU 61 controls the operation panel 67, the I / F unit 63, the HDD 66, and the like, reads out these control programs from the ROM 65, executes various controls, and performs serial communication with the engine CPU 62. The image data and information data required by the engine CPU 62 are transferred.

The clock 61a is backed up by a battery and can operate even when the power source 73 of the printer 1 is turned off. The current time serving as a basis for specifying various operation timings of the printer 1 is sent to the printer controller CPU 61. Output.
The engine CPU 62 executes mechanical control of the image processing unit 3 and the fixing unit 5 while acquiring signals from the power source 73 of the printer 1 and the open / close switch 75 that detects the open / close state of the open / close door 74. Then, a necessary program is read from the ROM 68b, and execution of a warm-up operation, a white streak generation prevention process described later, and the like is controlled.

  Although the printer controller CPU 61 and the engine CPU 62 are activated at the same time when the power source 73 of the printer 1 is turned on, the time required for completion of startup depends on the configuration of the device, but usually the printer controller CPU 61 The rise is slower. That is, the printer controller CPU 61 reads out these programs from the ROM 65 in order to perform data processing of input image data and execution of complex programs for executing smooth print processing while taking the overall timing. This is because it takes time to complete the start-up.

Therefore, the control that needs to be executed before the printer controller CPU 61 is started up is executed under the independent control of the engine CPU 62.
Here, since the current time is information managed only by the printer controller CPU 61 and the engine CPU 62 cannot directly acquire the current time, the current time is used for control in the independent control by the engine CPU 62. The restriction that it is not possible occurs.

Due to this restriction, for example, the time from a certain time stored in the memory to the present time cannot be calculated.
However, the engine CPU 62 incorporates a clock 62a that is asynchronous with the above-mentioned clock 61a. By counting up signals periodically output from the clock 62a, the engine CPU 62 grasps the time from the start of counting up to the present time. can do.

The clock 62a may be provided outside the engine CPU 62.
The I / F unit 63 is a LAN card, a LAN board, or the like for connecting the printer controller CPU 61 to a network such as a LAN. The I / F unit 63 receives print jobs, image data, and the like transmitted from the client terminal via the LAN. Receive and send to the printer controller CPU 61.

A RAM (Random Access Memory) 64 is a volatile memory and serves as a work area when the printer controller CPU 61 executes a program.
A ROM (Read Only Memory) 65 stores a communication program with the operation panel 67 and external devices, a control program for managing the entire printer 1 and the like.
An HDD (Hard disk drive) 66 mainly stores image data.

An EEPROM (Electronically Erasable and Programmable Read Only Memory) 68 a is a non-volatile memory and serves as a data storage area of the engine CPU 62.
The ROM 68b includes various control programs such as the image processing unit 3, the paper feeding unit 4, and the fixing unit 5, a program related to image stabilization processing such as automatic density adjustment and registration correction, and an execution program for white stripe generation prevention processing. The program is stored.
(White stripe generation prevention treatment)
In the printer 1 of the present embodiment, discharge products such as nitrogen oxides generated due to corona discharge of the chargers 32M to 32K adhere to the surface of the photosensitive drums 31Y to 31K with time, and white stripes are generated. In order to prevent the occurrence of white stripes, the photosensitive drums 31Y to 31K are rotated (split) independently of the image forming operation, and the discharge products attached to the surface are removed by the cleaning members 35Y to 35K. To do.

In this idling, there is no need to carry toner images on the photosensitive drums 31Y to 31K.
However, since the toner contains an external additive having lubricity, in order to reduce the deterioration of the photosensitive drums 31Y to 31K, the toner drum 31Y to 31K is rotated while carrying the toner image. May be. (Please check the underlined section below.)
FIG. 3 is a flowchart showing the contents of the white streak generation prevention process executed by the engine CPU 62, and is executed as a subroutine of a main routine (not shown) for controlling the entire apparatus.

  First, for example, the engine CPU 62 determines whether or not a signal indicating that the power source 73 is turned on and the casing door 74 is closed is output from the power source 73 and the open / close switch 75 of the printer 1. If the output of such a signal is not confirmed (step S100: NO), the process directly returns to the main routine, and if the output of the signal as described above is confirmed (step S100: YES). ) When the warm-up execution is determined, the current time is notified to the printer controller CPU 61 (step S101: YES), the value of the flag K stored in the EEPROM 68a is set to 0, and At the time of stop corresponding to each of the photosensitive drums 31Y to 31K stored in the EEPROM 68a Among them, the time from the oldest time to the current time is calculated to obtain the stop time of the photosensitive drum (step S103), and the humidity in the apparatus is obtained from the in-machine humidity sensor 70 (step S104). .

Here, the stop time corresponding to the photosensitive drums 31Y to 31K corresponds to the starting point of the period from the rotation of each of the photosensitive drums 31Y to 31K to the present while maintaining the stopped state. This is the time, and when it is currently rotating, the stop time is cleared.
That is, every time each of the photosensitive drums 31Y to 31K stops, the engine CPU 62 writes the current time as a stop time in the storage area in the EEPROM 68a corresponding to the stopped photosensitive drum, and each of the photosensitive drums 31Y to 31Y. Each time any of 31K starts to rotate, the stop time stored in the storage area in the EEPROM 68a corresponding to the photosensitive drum that has started the rotation is cleared.

  On the other hand, when the printer controller CPU 61 is requested to notify the current time, but the time-out occurs without being notified (step S101: NO), the value of the flag K stored in the EEPROM 68a is set to 1 (step S105). ), Temperature signals indicating the temperature t1 of the fixing unit 5 and the temperature t2 in the printer 1 are acquired from the temperature sensor 54 and the in-machine temperature sensor 69, respectively (step S106), and a temperature difference S obtained by subtracting t2 from t1 is calculated. Then (step S107), the process proceeds to the steps after the above-described step S104 for acquiring the humidity in the apparatus from the in-machine humidity sensor 70.

Here, if the temperature difference S is large, it is estimated that the fixing unit 5 is currently in a high temperature state and the image forming operation has been executed in the past.
Conversely, when the temperature difference S is small, it is presumed that the fixing unit 5 is currently in a state close to room temperature and the image forming operation has not been executed for a long time.
Then, the accumulated rotational speed of each of the photosensitive drums 31Y to 31K is acquired from the EEPROM 68a (step S108), and this is divided by the serviceable rotational speed of each of the photosensitive drums 31Y to 31K to calculate the degree of deterioration of each of the photosensitive drums. Of these, the largest value is set as the degree of deterioration used for control (step S109). Next, when the value of the flag K is 0 (step S110: YES), the photosensitive drum is based on the table 1 described later. For all of 31Y to 31K, the length of time for performing idling is determined (step S111), and when the determined execution time is 0 (step S112: YES), without performing idling, Return to the main routine.

Here, the cumulative rotational speed is stored in a storage area corresponding to each of the photosensitive drums 31Y to 31K of the EEPROM 68a, and a value having 0 as an initial value is stored, and this value is stored by the engine CPU 62. This is incremented by 1 every time the photosensitive drum corresponding to the area is rotated once.
The reason why the degree of deterioration of each photosensitive drum is assumed to be uniform is that the photosensitive drum may be replaced with a new one by maintenance or the like.

When the photosensitive drum is replaced, the accumulated rotational speed is reset to 0 by a service person or the like.
On the other hand, if the determined execution time is not 0 (step S112: NO), idling for the determined time is executed in parallel with the warm-up operation (step S113), and the process returns to the main routine.

Here, the warm-up operation is a series of operations that are executed to preheat the fixing unit 5 when the power is turned on and when the door of the housing that has been opened after the jam processing is finished is closed. Say.
The reason why the idling is performed in parallel with the warm-up operation is to reduce the waiting time during which the image forming operation cannot be performed as much as possible.

If the value of the flag K is not 0 (step S110: NO), the length of time for performing idling is determined for all of the photosensitive drums 31Y to 31K based on the table 2 described later (step S110). In step S114, the process proceeds to step S112 and subsequent steps in which it is determined whether or not the determined execution time is zero.
Hereinafter, the table 1 and the table 2 used for deriving the idle running time will be described.

FIG. 4A is a diagram showing a table 1 for deriving the idling execution time in accordance with the three factors of the photosensitive drum stop time, the humidity inside the apparatus, and the degree of deterioration of the photosensitive drum. .
Here, there are three cases where the conditions for the stop time of the photosensitive drum are less than 8 hours, 8 hours or more, less than 16 hours, and 16 hours or more.
Further, the humidity is classified into three categories of less than 15%, 15% or more, less than 70%, and 70% or more for each stop time category.

Further, the degree of deterioration of the photoreceptor is divided into two categories of less than 90% and 90% or more for each humidity category.
As can be seen from the figure, when both the stop time and the humidity are low (the stop time is less than 8 hours and the humidity is less than 15%), the idling time is determined to be 0 seconds regardless of the degree of deterioration of the photoreceptor. When both the stop time and the humidity are high (the stop time is 16 hours or more and the humidity is 70% or more), the idling time is determined to be 20 seconds regardless of the degree of deterioration of the photoreceptor.

In other ranges, 0 or 20 seconds is determined according to the degree of deterioration of the photosensitive member, and a finer execution time that matches the actual situation is determined.
Hereinafter, the reason why the execution time for executing idling is set to 20 seconds will be described.
FIG. 5 is a diagram showing the basis for derivation of the table 1.

More specifically, in the figure, the execution time of idling is changed for a photoconductor having a stop time of 16 hours or more, an in-machine humidity of 70% or more, and a deterioration degree of 90% or more. In other words, in the photosensitive drum in the most severe condition, the idle running time is changed, and the degree of elimination of white streak generation is evaluated stepwise by visual inspection.
As shown in the figure, the longer the idling execution time, the smaller the white generation level. When the idling execution time was 20 seconds, the white generation level was within the allowable level range.

For this reason, the running time for idling is set to 20 seconds.
Note that the time required for the fixing unit 5 to rise to the fixing temperature, that is, the time required for the warm-up operation, tends to be shortened in recent years as the fixing unit is improved, but it still takes about 30 seconds. Even if the rotation is carried out for 20 seconds, it can be completed within the warm-up operation time.

FIG. 4B shows the table 2.
Here, the temperature difference S is used instead of the stop time.
The inventors have empirically estimated that when the temperature difference S is 100 ° C. or more, it corresponds to the case where the stop time is less than 8 hours.
For this reason, the idling time in the frame of “temperature difference S is 100 ° C. or higher” in Table 2 is the same as the method of determining the idling time in the frame of “stop time less than 8 hours” in Table 1. I have to.

Further, the inventors speculated that when the temperature difference S is less than 100 ° C., this corresponds to a case where the stop time is 8 hours or more.
On the other hand, in Table 1, there are two cases where the stop time is 8 hours or more and less than 16 hours and 16 hours or more, and the idle time is determined more finely.
Therefore, the inventors adopted one of these two cases that is considered to have a higher white stripe prevention effect.

In other words, the idling time in the frame of “temperature difference S is less than 100 ° C.” in Table 2 is the same as the method of determining the idling time in the frame of “stop time of 16 hours or more” in Table 1. did.
Here, the reason for deriving Table 1 will be described.
FIG. 6A shows the result of evaluating the occurrence of white streaks due to differences in the stop time of the photosensitive drum and the humidity in the apparatus when the degree of deterioration of the photosensitive drum is less than 90%.

As shown in FIG. 6A, white streaks are more likely to occur as the photosensitive drum stop time and the humidity in the apparatus increase.
“X” in the figure means that white streaks are generated, and “Δ” means that there is a portion where the image density is thin, but it is within an allowable range.
Therefore, the inventors determined whether or not to execute the white stripe generation prevention process in consideration of only “x” in the figure.

FIG. 6B shows the result of evaluating the occurrence of white streaks due to differences in the stop time of the photosensitive drum and the humidity in the apparatus at the end of the lifetime when the degree of deterioration of the photosensitive drum is 90% or more.
As shown in FIG. 6B, it can be seen that white stripes are likely to occur when the photosensitive drum reaches the end of its life.

This is presumably because the surface of the photosensitive drum is scraped, the surface texture becomes rough, and discharge products are easily attached.
For this reason, in the table 1, conditions for performing idling at the end of the life of the photosensitive drum are strict.
As described above, the table 1 is created based on the results shown in FIGS. 6 (a) and 6 (b).

As described above, according to the present embodiment, the idling time is determined based on the three factors of the photosensitive drum stop time, the humidity in the apparatus, and the degree of deterioration of the photosensitive drum. The occurrence of white stripes can be predicted with high accuracy.
Further, when the determined execution time is 0, since the idling is not executed even during the warm-up operation, the life of the photosensitive drum can be extended.

Furthermore, when the determined execution time is not 0, the idle rotation is executed in parallel with the warming-up operation for that time, so that the occurrence of white stripes can be prevented.
<Modification>
As described above, the present invention has been described based on various embodiments. However, the content of the present invention is not limited to the above embodiments, and for example, the following modifications can be considered. .

(1) In the above embodiment, the idle rotation is performed using the table for deriving the idle rotation execution time according to the three factors of the photosensitive drum stop time, the humidity in the apparatus, and the degree of deterioration of the photosensitive drum. However, the execution time is not limited to this.
The stop time of the photosensitive drum, which is largely caused by the adhesion of the discharge product to the photosensitive drum, is essential as an element for deriving the running time of the idling, but the humidity in the machine and the degree of deterioration of the photosensitive drum are You may create the table which determines the execution time of idling using only one of them.

In that case, for example, in Table 1, a new table is created assuming that the missing elements (in-machine humidity or the degree of deterioration of the photosensitive drum) are on the disadvantageous side for white streaking. It is desirable to do.
By doing in this way, it is possible to determine the execution time of idling based on the safety standard, and it is possible to reliably prevent the occurrence of white stripes.

(2) In the above embodiment, the stop time of the photosensitive drum is estimated using the temperature difference S obtained by subtracting the in-machine temperature t2 of the printer 1 from the temperature t1 of the fixing unit 5, but the temperature t1 Since the change in the temperature t2 is small with respect to the change in temperature, the stop time of the photosensitive drum may be estimated using only the temperature t1 of the fixing unit 5 without considering the change in the temperature t2.
(3) In the above embodiment, the photosensitive drums 31Y to 31K are configured to be rotationally driven all at once by the same drive source, but the present invention is not limited to this configuration.

For example, separate driving sources may be provided for the color photosensitive drums 31Y to 31C and the monochrome photosensitive drum 31K, or a driving source may be provided for each of the photosensitive drums 31Y to 31K. .
In this way, it is possible to execute the white stripe generation prevention process more finely by changing the idle rotation time for each drive source.

In this case, in step S109 in FIG. 3, the degree of deterioration of each photosensitive drum is calculated, and the largest value among them is set as the degree of deterioration used for control. The idle rotation time is determined for each of the drums 31Y to 31C.
(4) Further, in the above-described embodiment, the cumulative rotation number corresponding to each of the photosensitive drums 31Y to 31K divided by the durable rotation number is used as the deterioration degree. If there is no difference between 31K, the cumulative number of revolutions itself may be used as the degree of deterioration to control white stripe generation prevention processing.

(5) In the above embodiment, the time for performing idling is set to 20 seconds. However, this is merely an example, and may be changed depending on the outer diameter or material of the photosensitive drum as needed. The value should be changed.
Furthermore, although the time for performing idling is fixed at 20 seconds, the white streak estimated from the three factors of the photosensitive drum stop time, the humidity in the machine, and the degree of deterioration of the photosensitive drum. Variations may be provided in the idling time depending on the ease of occurrence.

Further, it is desirable to set the idling time to be equal to or less than the warm-up operation time at the longest.
Here, since the warm-up operation ends when the temperature of the fixing unit 5 reaches a predetermined temperature, the exact time required for the warm-up operation is not known in advance.
Therefore, the end of the warm-up operation may be detected and the idle rotation may be terminated, or the shortest warm-up operation time t _ws obtained empirically and the maximum idle time defined in Table 1 and Table 2 _May be set to be equal to or less than _tws .
(6) Further, in the above-described embodiment, the configuration in which the photosensitive drum is the one to be charged by the charger has been described as an example. However, an endless photosensitive belt is used instead of the photosensitive drum. In short, it is only necessary to be an image bearing rotating body that can carry and rotate a toner image.
(7) Although the tandem type color printer has been described in the above embodiment, the present invention is not limited to this, and may be, for example, a monochrome printer, and further has additional functions such as a copying machine and a fax machine. It may be a device.

  The present invention can be widely applied to an image forming apparatus including an image bearing rotating body that carries a toner image by being charged by a charger.

1 is a schematic cross-sectional view showing the overall configuration of a tandem color digital printer according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a control unit of the printer according to the embodiment of the present invention. It is a flowchart which shows the content of the white stripe generation | occurrence | production prevention process performed with the engine CPU which concerns on embodiment of this invention. (A) shows the table 1 which concerns on embodiment of this invention, (b) is a figure which shows the table 2 which concerns on embodiment of this invention. It is a figure which shows the derivation | leading-out ground of the table 1 which concerns on embodiment of this invention. FIG. 6A shows the result of evaluating the occurrence of white streaks due to the difference between the stop time of the photosensitive drum and the humidity in the apparatus when the degree of deterioration of the photosensitive drum is less than 90%. ) Is a result of evaluating the occurrence of white streaks due to differences in the stop time of the photosensitive drum and the humidity in the machine at the end of the life when the degree of deterioration of the photosensitive drum is 90% or more.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 3 Image process part 3Y, 3M, 3C, 3K Image creation part 4 Paper feed part 5 Fixing part 10 Optical part 11 Intermediate transfer belt 12 Drive roller 13 Driven roller 31Y, 31M, 31C, 31K Photosensitive drum 32Y, 32M, 32C, 32K charger 33 developing device 34 primary transfer roller 35 cleaning member 41 paper feed cassette 42 feeding roller 43 transport path 44 timing roller pair 45 secondary transfer roller 46 secondary transfer position 51 fixing roller 52 induction coil 53 pressure roller 54 Temperature sensor 60 Control unit 61 Printer controller CPU
61a Clock 62 Engine CPU
62a clock 63 I / F section 64 RAM
65 ROM
66 HDD
67 Operation panel 68a EEPROM
68b ROM
68c RAM
69 In-machine temperature sensor 70 In-machine humidity sensor 71 Discharge roller pair 72 Discharge tray 73 Power supply 74 Open / close door 75 Open / close switch

Claims (3)

An image forming apparatus that charges while rotating an image bearing rotator, and forms a toner image on a peripheral surface of the charged image bearing rotator,
A cleaning member that comes into contact with the peripheral surface of the image bearing rotor and removes deposits on the peripheral surface;
A warm-up determination means for determining execution of the warm-up operation;
First index value acquisition means for acquiring a stop time index value that indicates the stop time from when the previous image carrying rotator stopped until its current state has been maintained;
Second index value acquisition means for acquiring at least one index value among a humidity index value indicating the humidity in the apparatus and a deterioration degree index value indicating the current deterioration degree of the image bearing rotator;
When execution of the warm-up operation is determined,
Based on the stop time index value acquired by the first index value acquisition means and the at least one index value acquired by the second index value acquisition means, the image carrier rotator is idled. Determine the execution time to be executed,
If the determined execution time is not 0, in parallel with the warming-up, the idle rotation of the image bearing rotating body is executed for the execution time,
If the determined execution time is 0, control means for controlling not to execute the idle rotation ;
A memory storing a stop time at which the image bearing rotator changes from a rotating state to a stopped state;
A clock that outputs the current time, and
Transfer means for transferring a toner image carried on the image carrying rotating body to a sheet;
A fixing unit that heats and pressurizes the sheet on which the toner image is transferred, and fixes the toner image to the sheet;
Temperature detecting means for detecting the temperature of the fixing unit ,
The second index value acquisition means acquires the humidity index value and the deterioration degree index value,
The control means compares the stop time index value, the humidity index value, and the deterioration degree index value with thresholds corresponding to these, and classifies the cases, and sets the time associated with each case in advance. When the execution time of the warm-up operation is determined and the current time can be acquired, the time from the stop time to the current time is selected as the stop time index value. When the current time cannot be acquired, the stop time index value is estimated based on the temperature of the fixing unit . The image forming apparatus according to claim 1 includes a plurality of image bearing rotators and one driving unit that rotationally drives each image bearing rotator.
The second index value acquisition means acquires a degradation degree index value for each image bearing rotator,
The control means includes
The idle rotation execution time of all the image carrying rotators is determined based on the largest degradation degree index value among the degradation degree index values acquired for each image carrying rotator. The image forming apparatus according to 1. The control means includes
3. The image forming apparatus according to claim 1, wherein when the warm-up operation is completed, an execution time of the idle rotation is determined so that the idle rotation is completed.

Images