JP7224143B2 - Image forming apparatus and charging bias control method - Google Patents

Description

The present invention relates to an image forming apparatus and the like, and more particularly to an image forming apparatus capable of forming images on both sides of a recording medium.

Conventionally, in an electrophotographic image forming apparatus, when a photosensitive drum is charged, even if the same charging bias is applied to the photosensitive drum, how long has the photosensitive drum been used, and how long has the photosensitive drum been used? The amount of charge on the surface of the photoreceptor changes depending on the environment.

Therefore, in order to always obtain a stable image, it is necessary to correct the charging bias applied to the photosensitive drum according to the state of the photosensitive drum and the surrounding environment.

As a conventional technique, for example, in an image forming apparatus, VL A proposal has been made to perform appropriate image formation control by predicting fluctuations due to up and down VL (see Patent Document 1).

Here, the potential of the portion of the electrostatic latent image formed on the surface of the photoreceptor by irradiating the photoreceptor charged to a certain potential with light is defined as VL.

JP 2009-288307 A

However, the technique of Patent Document 1 is based on the results of predicting variations due to VL up and VL down from information such as photoreceptor rotation time, photoreceptor stop time, temperature of ambient environment, and absolute humidity of ambient environment. I tried to control the bias, but it was not compatible with double-sided printing.

In particular, in a monochrome image forming apparatus, when double-sided printing is performed, the paper that has passed through the fixing once comes into contact with the photoreceptor drum again. spreads. As a result, there arise problems that the density of the image is reduced and the carrier is expelled from the developing device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of reducing image defects that occur during double-sided printing.

The present invention relates to an image forming apparatus configured to be capable of forming images on both sides of a recording medium, comprising a photosensitive drum and a surface of the photosensitive drum that is charged by applying a charging bias to the surface of the photosensitive drum. an exposure device that exposes the photosensitive drum to form a latent image; a developing device that develops the latent image by applying toner; and a storage that stores a printing history. a correction amount determination unit that determines a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history; and a correction that corrects the bias value of the charging bias based on the correction amount. and a part.

The present invention also provides a charging bias control method for an image forming apparatus configured to be capable of forming images on both sides of a recording medium, wherein a charging bias is applied to the surface of a photoreceptor drum so that the surface of the photoreceptor drum is charging; exposing the photosensitive drum to form a latent image; developing the latent image by applying toner; storing a print history; determining a correction amount of the bias value of the charging bias based on printing history; and correcting the bias value of the charging bias based on the correction amount. .

According to the image forming apparatus of the present invention, the image forming apparatus is configured to be capable of forming images on both sides of a recording medium. an image forming unit having a charging device that charges the surface of the photoreceptor drum, an exposure device that exposes the photoreceptor drum to form a latent image, and a developing device that develops the latent image by applying toner; a storage unit for storing a history; a correction amount determination unit for determining a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history; and a correction amount of the charging bias based on the correction amount. By providing a correction unit for correcting the bias value, it is possible to correct the bias value of the charging bias according to the history of double-sided printing, and apply an appropriate charging bias to the photosensitive drum. It is possible to provide an image forming apparatus capable of reducing image defects that occur during double-sided printing.

Further, according to the charging bias control method of the present invention, it is a charging bias control method for an image forming apparatus configured to be capable of forming images on both sides of a recording medium, wherein the charging bias is applied to the surface of the photosensitive drum. a step of charging the surface of the photoreceptor drum by exposing the photoreceptor drum to form a latent image; a step of attaching toner to develop the latent image; a step of storing a printing history; determining a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history; and correcting the bias value of the charging bias based on the correction amount. Therefore, the bias value of the charging bias can be corrected according to the history of double-sided printing, and an appropriate charging bias can be applied to the photoreceptor drum. It is possible to provide an image forming apparatus capable of

1 is a block diagram showing the configuration of an image forming apparatus according to a first embodiment; FIG. 2 is an explanatory diagram showing a schematic configuration of the image forming apparatus; FIG. 5 is a flow chart showing a printing operation including correction of a bias value of charging bias in double-sided printing by the image forming apparatus; FIG. 3 is an explanatory diagram showing a table for specifying a basic correction amount of a bias value correction amount of a charging bias for charging a photosensitive drum in double-sided printing of the image forming apparatus according to the number of double-sided printing sheets and an external temperature; FIG. 5 is an explanatory diagram showing a table for specifying a coefficient K1 according to process speed for setting the correction amount; FIG. 5 is an explanatory diagram showing a table for specifying a coefficient K2 based on a fixing temperature for setting the correction amount; FIG. 11 is an explanatory diagram showing a table for specifying a coefficient K3 according to a printing paper size for setting the correction amount; FIG. 4 is an explanatory diagram showing a table for specifying a coefficient K4 based on the elapsed time from the start of double-sided printing executed in the image forming apparatus and the external temperature; FIG. 11 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when double-sided printing was performed 30 minutes ago in the image forming apparatus; FIG. 10 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when double-sided printing was performed 15 minutes ago in the image forming apparatus; FIG. 11 is an explanatory diagram showing a table for specifying a coefficient K5 according to the operation state of the cooling fan when left after duplex printing in the image forming apparatus according to the second embodiment; 4 is an explanatory diagram showing a table for specifying usage states of photoreceptor drums in the image forming apparatus; FIG. FIG. 10 is an explanatory diagram for determining a charging bias correction amount based on the history of double-sided printing, the operation state of a cooling fan, and the life of a photosensitive drum when double-sided printing was performed 30 minutes ago in the image forming apparatus; FIG. 10 is an explanatory diagram for determining a charging bias correction amount based on the history of double-sided printing, the operation state of a cooling fan, and the life of a photosensitive drum when double-sided printing was performed 15 minutes ago in the image forming apparatus; FIG. 12 is an explanatory diagram showing the progress of continuous double-sided printing in the image forming apparatus according to the third embodiment; FIG. 7 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when first double-sided printing is performed in the image forming apparatus; FIG. 10 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when double-sided printing is performed for the second time in the image forming apparatus; FIG. 11 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when double-sided printing is performed for the third time in the image forming apparatus;

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is an example of a mode for carrying out the invention, and is a block diagram showing the configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing the schematic configuration of the image forming apparatus. 2 is a flow chart showing a printing operation including correction of a bias value of a charging bias in double-sided printing by the image forming apparatus;

The first embodiment, as shown in FIG. 1, is an image forming apparatus 10 configured to be capable of forming images on both sides of a recording medium. A charging device 132 that charges the surface of the photosensitive drum 131 by applying voltage, an exposure device 133 that exposes the photosensitive drum 131 to form a latent image, and a developing device 134 that develops the latent image by adhering toner. and a storage unit 160 for storing the printing history, a correction amount determination unit 170 for determining the correction amount of the bias value of the charging bias, and a correction unit 180 for correcting the bias value of the charging bias. And, it is characterized by comprising.

The correction amount determining unit 170 extracts the double-sided printing history from the printing history stored in the storage unit 160, and determines the correction amount of the bias value of the charging bias based on the double-sided printing history. and

The correction unit 180 is characterized by correcting the bias value of the charging bias applied to the surface of the photosensitive drum 131 based on the correction amount determined by the correction amount determination unit 170 .

(Configuration of image forming apparatus)
First, the basic configuration of the image forming apparatus 10 according to the first embodiment will be described.
As shown in FIG. 2, the image forming apparatus 10 is an information processing apparatus that includes a document reading section 112 on the upper portion of the apparatus body, reads an image of a document, and outputs the image by an electrophotographic method.
1, the image forming apparatus 10 mainly includes a control unit 100, an image input unit 110, an image processing unit 120, an image forming unit 130, an operation unit 140, and a display unit 150. , and a storage unit 160 .

The control unit 100 is a functional unit for controlling the image forming apparatus 10 as a whole.
The control unit 100 implements various functions by reading and executing various programs, and is composed of, for example, one or a plurality of arithmetic units (for example, CPU (Central Processing Unit)).

The image input unit 110 is a functional unit for reading image data input to the image forming apparatus 10 . Image input unit 110 is connected to document reading unit 112 which is a functional unit for reading an image of a document, and receives image data output from document reading unit 112 .

Also, the image input unit 110 may input image data from a storage medium such as a USB (Universal Serial Bus) memory or an SD card. Further, the image data may be input from the other terminal device by providing a communication unit for connecting with the other terminal device.

The image processing unit 120 is a functional unit for forming output data based on image data on a recording medium (for example, recording paper). For example, as shown in FIG. 2 , recording paper is fed from a paper feed tray 122 , an image is formed on the surface of the recording paper in the image processing section 120 , and then the paper is discharged from a paper discharge tray 124 . The image processing unit 120 is configured by, for example, a laser printer using an electrophotographic method.

The image forming unit 130 is a functional unit that performs various types of image processing on image data. Then, an output image is formed based on the image data subjected to image processing.

Specifically, as shown in FIG. 1, a charging device 132 applies a charging bias to the surface of the photoreceptor drum 131 to charge the surface of the photoreceptor drum 131 . Then, an electrostatic latent image is formed on the surface of the photosensitive drum 131 charged by the exposure device 133 . Then, a toner image is formed on the surface of the photosensitive drum 131 by the developing device 134 . The toner image formed on the surface of the photoreceptor drum 131 is transferred to recording paper and output as a printed matter.

The operation unit 140 is a functional unit for receiving an operation instruction from a user, and includes various key switches, a device for detecting input by contact, and the like. The user inputs functions to be used and output conditions via the operation unit 140 . The display unit 150 is a functional unit for displaying various information to the user, and is configured by, for example, an LCD (Liquid crystal display).

Note that the image forming apparatus 10 may include a touch panel in which the operation unit 140 and the display unit 150 are integrally formed, as shown in FIG. In this case, the method of detecting the touch panel input may be a general detection method such as a resistive film method, an infrared method, an electromagnetic induction method, or an electrostatic capacitance method.

The storage unit 160 is a functional unit that stores various programs and various data necessary for the operation of the image forming apparatus 10 . The storage unit 160 is configured by, for example, a semiconductor memory such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

In the first embodiment, the storage unit 160 stores a user's job history (job log). The job history stores the history of double-sided printing.

Here, a characteristic configuration of the image forming apparatus 10 of the first embodiment will be described.
The image forming apparatus 10 of the first embodiment is characterized by including a correction amount determination unit 170 that determines the correction amount of the bias value of the charging bias, and a correction unit 180 that corrects the bias value of the charging bias.

In the first embodiment, the correction amount determination unit 170 determines how much double-sided printing has been performed in the past for the latest printing operation including single-sided printing, according to the driving of the charging device (for example, charging roller) 133 during double-sided printing. The amount of correction is determined depending on whether or not the correction has been performed.

(Regarding charging bias correction during double-sided printing)
Next, in the image forming apparatus 10 of the first embodiment, the procedure for determining the charging bias correction amount when applying the charging bias to the photosensitive drum 131 will be described with reference to a flowchart.
FIG. 3 is a flow chart showing the procedure for determining the charging bias correction amount when charging the photosensitive drum in the image forming apparatus of the first embodiment.

When the image forming apparatus 10 performs print processing, as shown in FIG. 3, first, a request to start printing is made (step S101). Then, in the first embodiment, it is determined whether or not there is a history of double-sided printing within the past four hours (step S103).

In step S103, if it is determined that there is a history of double-sided printing within the past 4 hours, a charging bias correction value and coefficient are calculated according to the history of one cycle of double-sided printing, and based on the correction value and coefficient. A charging bias correction amount is determined (step S105). Here, it is calculated based on the history of recent double-sided printing. Then, printing is started (step S109).

The history of double-sided printing includes, for example, the number of copies printed, the environment (temperature) at the time of printing, the process speed, the fixing temperature, the paper size, the time the printing was performed, the environment in which it was left, and the temperature of the cooling fan inside the device at the time of leaving. Information for double-sided printing, such as the operating state and the life of the photoreceptor drum (durable number of rotations), is stored.

On the other hand, if it is determined in step S103 that there is no double-sided printing history within the past four hours, the charge bias correction amount is set to 0 (step S107), and printing is started (step S109). When printing starts, the storage unit 160 stores the printing start time.

Then, in step S111, it is determined whether or not printing has been interrupted.
If it is determined in step S111 that printing has been interrupted, the printing process is resumed after the cause of the interruption is resolved (step S113). Then, the process returns to step S103, and whether or not there is a double-sided printing history is determined again.

On the other hand, if it is determined in step S111 that printing has not been interrupted, the printing process is continued and terminated (step S115). Then, the process of correcting the charging bias applied to the surface of the photoreceptor drum 131 ends.

(Method for Determining Charge Bias Correction Amount)
Next, a method of determining a correction amount when correcting the bias value of the charging bias applied to charge the photosensitive drum 131 in the image forming apparatus 10 will be described.

FIG. 4 shows a table for specifying the basic correction amount of the correction amount of the bias value of the charging bias for charging the photosensitive drum in double-sided printing of the image forming apparatus according to the first embodiment by the number of double-sided prints and the external temperature. FIG. 5 is an explanatory view showing a table specifying the coefficient K1 based on the process speed for setting the correction amount; FIG. 6 is an explanatory view showing a table specifying the coefficient K2 depending on the fixing temperature for setting the correction amount; FIG. 7 is an explanatory diagram showing a table for specifying the coefficient K3 according to the printing paper surface size for setting the correction amount; FIG. FIG. 10 is an explanatory diagram showing a table specifying coefficient K4 according to external temperature;

In the first embodiment, in the image forming apparatus 10, the amount of correction of the bias value of the charging bias applied to the photoreceptor drum 131 during printing is determined based on the history of double-sided printing in the printing history. As information for double-sided printing based on the history of double-sided printing, determination is made using process speed, fixing temperature, paper size, elapsed time after performing double-sided printing, and leaving environment.

Assuming that the correction amount for double-sided printing is "H",
H = Σ (Ha x K1 x K2 x K3 x K4)
becomes.
and each sign is
Ha: Basic correction amount for one cycle of double-sided printing K1: Coefficient based on process speed K2: Coefficient based on fixing temperature K3: Coefficient based on paper size K4: Coefficient based on elapsed time after double-sided printing and leaving environment (temperature).

As shown in FIG. 4, the basic correction amount Ha for one cycle of double-sided printing is specified based on a table of the number of sheets in one cycle of double-sided printing and the external temperature as environment information around the apparatus.
In the first embodiment, for example, the number of double-sided printing is set to 0 to 15 (sheets), 16 to 30 (sheets), 31 to 45 (sheets), 46 to 60 (sheets), 61 to 75 (sheets), 76 ~ 90 (sheets), 91 (sheets) or more, the external temperature is 7 degrees or less, 7.1 to 14 (°C), 14.1 to 21 (°C), 21.1 to 28 (°C), The basic correction amount is specified on the table corresponding to 28.1 to 35 (°C) and 35.1 (°C) or more. For example, if the number of double-sided printed sheets is 30 and the external temperature is 5 degrees, the basic correction amount Ha is "-6".

It can be inferred that the higher the number of printed sheets and the lower the external temperature, the higher the photoreceptor drum surface temperature. Therefore, the larger the number of printed sheets and the lower the external temperature, the larger the charging bias correction amount.

The coefficient K1 depending on the process speed is, as shown in FIG. /s), 301 to 350 (mm/s), and 351 to 400 (mm/s), so that the values are specified on the table so that the numerical values decrease by 0.05 from 1.15 to 0.9. I have to.

It can be inferred that the slower the process speed, the longer the contact time between the photoreceptor drum and the recording paper, and thus the greater the increase in the surface temperature of the photoreceptor drum. Therefore, the slower the process speed, the larger the coefficient K1.

The coefficient K2 depending on the fixing temperature is, as shown in FIG. , the numerical values are specified on the table so as to increase by 0.05 from 0.9 to 1.1.

The higher the fixing temperature, the higher the surface temperature of the paper surface. Therefore, the higher the fixing temperature, the larger the coefficient K2.

As shown in FIG. 7, the coefficient K3 depending on the printing direction paper size is, for example, paper size 100 (mm) or less, 101 to 150 (mm), 151 to 200 (mm), 201 to 250 (mm), 251 to 300 (mm), 301 to 350 (mm), and 351 (mm) or more are specified on the table so that the numerical values increase by 0.05 from 0.8 to 1.1.

It is presumed that the longer the paper size, the longer the contact time between the paper surface and the photoreceptor drum, and thus the greater the increase in the surface temperature of the photoreceptor drum. Therefore, the longer the page size, the larger the coefficient K3.

As shown in FIG. 8, the coefficient K4 based on the elapsed time after double-sided printing and the external temperature is, for example, the external temperature for every 5 minutes from 5 minutes or less to 235 minutes or more. 7 degrees or less, 7.1 to 14 (°C), 14.1 to 21 (°C), 21.1 to 28 (°C), 28.1 to 35 (°C), 35.1 (°C) or more are used to identify numerical values on the table.

If the standing temperature is low, the drum surface temperature drops rapidly in a short time, and as the standing temperature rises, the surface temperature becomes more difficult to drop. Therefore, if the storage temperature is low, the coefficient is extremely decreased as time passes. When the storage temperature is high, the coefficient K4 is gradually decreased as time passes.

(Regarding determination of charging bias correction amount based on double-sided printing history)
Next, regarding the correction amount of the charging bias when performing double-sided printing in the image forming apparatus 10 of the first embodiment, the correction amount based on the double-sided printing history when the double-sided printing was performed 30 minutes ago, and the correction amount based on the double-sided printing history A case will be described in which the charging bias correction amount is determined based on the correction amount based on the history of double-sided printing performed 15 minutes ago.

FIG. 9 is an explanatory diagram for determining the charging bias correction amount based on the history of double-sided printing when double-sided printing was performed 30 minutes ago in the image forming apparatus according to the first embodiment. FIG. 10 is an explanatory diagram for determining a charging bias correction amount based on a double-sided printing history when printing was performed 15 minutes ago;

The conditions for double-sided printing in the image forming apparatus 10 of the first embodiment are
・External environment: 5℃
・Charging roller bias of process control result: 1385 (V)
・Number of prints Ha: 50 sheets (30 minutes before), 30 sheets (15 minutes before)
・Process speed K1: 200mm/s
・Fixing temperature K2: 180°C
・Paper size K3: A4 (297mm)
・Elapsed time K4: 30 minutes before, 15 minutes before.

In the first embodiment, in the image forming apparatus 10, the correction amount of the bias value of the charging bias applied to the photosensitive drum 131 is set to the basic correction amount (Ha) according to the number of sheets of double-sided printing by the correction amount determination unit 170. Based on this, the process speed (K1), fixing temperature (K2), paper size (K3), and elapsed time (K4) are multiplied to calculate.

That is, if the correction amount for double-sided printing is "H",
H = Σ (Ha x K1 x K2 x K3 x K4)
becomes.

As shown in FIG. 9, the bias value correction amount (1) of the charging bias based on the history of double-sided printing 30 minutes ago is -18 for Ha, 1.1 for K1, and 0.95 for K2. , 1 of K3, and 0.15 of K4, the value of the coefficient is -2.8.

On the other hand, the bias value correction amount (2) of the charging bias based on the history of double-sided printing 15 minutes ago is, as shown in FIG. 0.95, 1 of K3, and 0.2 of K4, the values of the coefficients are multiplied to -1.3.

As a result, the charge bias correction amount H is the sum of the correction amount (1) and the correction amount (2).
i.e.
Charge bias correction amount H: (-2.8) + (-1.3) = (-4.1) (V)
becomes.

Then, the corrected charging bias value is calculated by the correction unit 180 .
i.e.
Corrected charging bias value: 1385+(-4.1)≈1381 (V)
(Rounded to the nearest whole number.)
becomes.

With the configuration as described above, according to the first embodiment, in the image forming apparatus 10, the correction amount determining unit 170 that determines the correction amount H of the bias value of the charging bias and the correction amount determining unit 170 that corrects the bias value of the charging bias. Further, the correction amount determination unit 170 extracts the double-sided printing history from the printing history stored in the storage unit 160, and calculates the bias value of the charging bias based on the double-sided printing history. By determining the correction amount H of , it is possible to apply an appropriate charging bias to the photosensitive drum 131, so that it is possible to reduce image defects that occur during double-sided printing.

(Second embodiment)
Next, a second embodiment will be described.
In the image forming apparatus 10 of the first embodiment, in addition to parameters such as the process speed and fixing temperature based on the history of double-sided printing, the image forming apparatus 10 of the first embodiment further uses the operation of the cooling fan. The charging bias correction amount is determined by adding the condition and the life of the photosensitive drum to the parameters.

In addition, in 2nd Embodiment, for convenience of explanation, the same number is attached|subjected to the structure which has the same function as 1st Embodiment, and description is abbreviate|omitted.

FIG. 11 is an explanatory diagram showing a table for specifying the coefficient K5 according to the operating state of the cooling fan when left after duplex printing in the image forming apparatus according to the second embodiment, and FIG. FIG. 10 is an explanatory diagram showing a table for identifying usage states;

(Method for Determining Charge Bias Correction Amount)
In the second embodiment, in the image forming apparatus 10, the processing speed, the fixing temperature, the paper size, the elapsed time of the two-sided printing, and the leaving environment, which determine the correction amount of the charging bias in the first embodiment. In addition to the information at the time of double-sided printing based on , the operating state of the cooling fan when left after double-sided printing and the life of the photosensitive drum are used for determination.

Assuming that the correction amount for double-sided printing is "H",
H = Σ (Ha x K1 x K2 x K3 x K4 x K5 x K6)
becomes.
Each code, in addition to Ha, K1, K2, K3, and K4,
K5: Coefficient depending on the operating state of the cooling fan when left after double-sided printing K6: Coefficient depending on the life of the photosensitive drum.

As shown in FIG. 11, the coefficient K5 according to the operation state of the cooling fan after double-sided printing corresponds to, for example, the operating rate of the cooling fan of 0 (%), 1 to 50 (%), and 51 to 100 (%). are specified on the table so that the numerical values are 1.1, 1.05, and 1.

When the cooling fan is stopped, the temperature decreases slowly, so it can be assumed that the surface temperature of the photoreceptor drum 131 decreases less. Therefore, the lower the operating rate of the cooling fan, the larger the coefficient K5.

As shown in FIG. 12, the coefficient K6 of the drum life (life of the photosensitive drum) is, for example, 0 to 50 (k rotations) and 51 to 100 (k rotations) when the photosensitive drum is used as the drum life. , 101 to 150 (k rotations), and 151 (k rotations) or more are specified on the table so that the numerical values are 1, 1.05, 1.1, and 1.15.

As the life of the photoreceptor drum progresses, the response of the photoreceptor drum to the applied charging bias becomes dull. Therefore, the longer the life of the photosensitive drum, the larger the coefficient K6.

(Regarding determination of charging bias correction amount based on double-sided printing history)
Next, regarding the correction amount of the charging bias when performing double-sided printing in the image forming apparatus 10 of the second embodiment, as in the first embodiment, the history of double-sided printing when double-sided printing was performed 30 minutes before and the correction amount based on the history of double-sided printing when double-sided printing was performed 15 minutes ago.

FIG. 13 shows the charging bias correction amount determined by the double-sided printing history, the operation state of the cooling fan, and the life of the photosensitive drum when the double-sided printing was performed 30 minutes ago in the image forming apparatus according to the second embodiment. FIG. 14 is an explanatory diagram for determining the charge bias correction amount based on the history of double-sided printing, the operation state of the cooling fan, and the life of the photosensitive drum when double-sided printing was performed 15 minutes ago in the image forming apparatus. is.

In the second embodiment, in addition to the conditions for double-sided printing in the image forming apparatus 10 of the first embodiment, the operational state of the cooling fan and the life of the photoreceptor drum are added, and the operating state of the cooling fan after double-sided printing. (Duty) K5: 50 (%)
・Photosensitive drum life (operating time) K6: 30 (k rotations)
and

Here, in the image forming apparatus 10, the correction amount of the bias value of the charging bias applied to the photosensitive drum 131 is determined by the correction amount determination unit 170 based on the basic correction amount (Ha) corresponding to the number of sheets printed on both sides. In addition to the coefficients of the process speed (K1), fixing temperature (K2), paper size (K3), and elapsed time (K4), the operating state of the cooling fan (K5) and the life of the photosensitive drum (K6) are multiplied. calculated by

That is, if the correction amount for double-sided printing is "H",
H = Σ (Ha x K1 x K2 x K3 x K4 x K5 x K6)
becomes.

As shown in FIG. 13, the bias value correction amount H30 of the charging bias based on the history of double-sided printing 30 minutes ago is a value of -18 for Ha, 1.1 for K1, 0.95 for K2, and 0.95 for K3. is 1, K4 is 0.15, K5 is 1.05, and K6 is 1, and the values of the coefficients are multiplied to -3.0.

On the other hand, the correction amount H15 of the bias value of the charging bias based on the history of double-sided printing 15 minutes ago is, as shown in FIG. , K3 of 1, K4 of 0.2, K5 of 1.05, and K6 of 1, the value of the coefficient is -1.3.

As a result, the charging bias correction amount H is the sum of the correction amount H30 and the correction amount H15.
i.e.
Charge bias correction amount H: (-3.0) + (-1.3) = (-4.3) (V)
becomes.

Then, the corrected charging bias value is calculated by the correction unit 180 .
i.e.
Corrected charging bias value: 1385+(-4.3)≈1381 (V)
(Rounded to the nearest whole number.)
becomes.

Comparing the charging bias correction amount in the second embodiment with the charging bias correction amount in the first embodiment, the correction amount is slightly different. It can be said that, in the second embodiment, the charging bias correction amount can be calculated more accurately by adding the coefficient K5 according to the operating state of the cooling fan and the coefficient K6 according to the life of the photosensitive drum.

With the configuration as described above, according to the second embodiment, in the image forming apparatus 10, the correction amount determining unit 170 that determines the correction amount H of the bias value of the charging bias and the correction amount determining unit 170 that corrects the bias value of the charging bias. The correction amount determination unit 170 is based on the history of double-sided printing stored in the storage unit 160, and further determines the operating state (K5) of the cooling fan in the apparatus and the life of the photosensitive drum ( By determining the bias value correction amount H of the charging bias based on K6), a more accurate correction amount of the charging bias can be calculated, and an appropriate charging bias can be applied to the photosensitive drum 131 .

(Third embodiment)
Next, a third embodiment will be described.
In the third embodiment, in the image forming apparatus 10 of the second embodiment, when performing continuous double-sided printing, if printing is interrupted by process control or the like and continuous printing is performed multiple times, The charge bias correction amount is determined based on the history of double-sided printing that has been executed.

In addition, in 3rd Embodiment, for convenience of explanation, the same number is attached|subjected to the structure which has the same function as 2nd Embodiment, and description is abbreviate|omitted.

FIG. 15 is an explanatory diagram showing the progress of continuous double-sided printing in the image forming apparatus according to the third embodiment, and FIG. 16 is a history of double-sided printing when the first double-sided printing is performed in the image forming apparatus. FIG. 17 is an explanatory diagram for determining the charging bias correction amount based on the history of double-sided printing when the second double-sided printing is performed in the image forming apparatus, and FIG. FIG. 11 is an explanatory diagram for determining a charging bias correction amount based on a history of double-sided printing when double-sided printing is performed for the third time in the image forming apparatus;

In the third embodiment, as shown in FIG. 15, when double-sided printing is continuously performed in the image forming apparatus 10, printing is interrupted twice, and as a result, double-sided printing is performed three times in a row. It was done by printing.

The conditions for double-sided printing in the image forming apparatus 10 of the third embodiment are
・External environment: 15°C
・Charging roller bias of process control result: 1300 (V)
・Number of prints Ha: 30 sheets per minute (90 sheets in 3 minutes) (first to third times)
・Process speed K1: 350mm/s
・Fixing temperature K2: 190°C
・Paper size K3: A4 (210mm)
・ Elapsed time K4: 10 minutes ago (1st time), 6 and a half minutes ago (2nd time), 3 and a half minutes ago (3rd time)
・Operating status of cooling fan after double-sided printing (Duty) K5: 100 (%)
・Photosensitive drum life (operating time) K6: 120 (k rotations)
and

In the third embodiment, in the image forming apparatus 10, the correction amount H of the bias value of the charging bias applied to the photoreceptor drum 131 is determined by the correction amount determination unit 170 based on the histories of the first to third double-sided printing. Then, the process speed (K1), fixing temperature (K2), paper size (K3), elapsed time (K4) coefficients, and cooling fan operating status are calculated based on the basic correction amount (Ha) according to the number of sheets printed on both sides. (K5) is calculated by multiplying the photoreceptor drum life (K6).
Then, the correction amount H of the bias value of the charging bias is obtained by summing the first to third correction amounts.

Let H1, H2, and H3 be the correction amounts H for double-sided printing each time.
H (H1, H2, H3) = Σ (Ha x K1 x K2 x K3 x K4 x K5 x K6)
becomes.

As shown in FIG. 16, the correction amount H1 for the bias value of the charging bias based on the history of the first double-sided printing is, as shown in FIG. 95, 0.35 of K4, 1 of K5, and 1.1 of K6 are multiplied, resulting in -3.1.

As shown in FIG. 17, the correction amount H2 for the bias value of the charging bias based on the history of the second double-sided printing is, as shown in FIG. 95, 0.35 of K4, 1 of K5, and 1.1 of K6 are multiplied, resulting in -3.1.

As shown in FIG. 18, the correction amount H3 of the bias value of the charging bias based on the history of the third double-sided printing is, as shown in FIG. 95, K4 of 1, K5 of 1, and K6 of 1.1 are multiplied, resulting in -8.9.

As a result, the correction amount H after performing double-sided printing three times in succession is the sum of the first correction amount H1, the second correction amount H2, and the third correction amount H3.
i.e.
Charge bias correction amount H: (-3.1) + (-3.1) + (-8.9)
= (-15.1) (V)
becomes.

Then, the corrected charging bias value is calculated by the correction unit 180 .
i.e.
Corrected charging bias value: 1300+(-15.1)≈1285 (V)
(Rounded to the nearest whole number.)
becomes.

Since it is configured as described above, according to the third embodiment, in the image forming apparatus 10, when determining the charging bias correction amount after performing two-sided printing continuously a plurality of times, After calculating the correction amount of the charging bias based on the history, by adding up the correction amounts of the charging bias for a plurality of times, the appropriate charging bias to be applied to the photosensitive drum 131 can be determined. Defects can be reduced.

As described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. It is clear that a person skilled in the art can conceive of various modifications or modifications within the scope of the claims. Embodiments obtained by combining technical means are also included in the technical scope of the present invention.

10 Image forming apparatus 100 Control unit 110 Image input unit 112 Document reading unit 120 Image processing unit 122 Paper feed tray 124 Paper discharge tray 130 Image forming unit 131 Photoreceptor drum 132 Charging device 133 Exposure device 134 Developing device 140 Operation unit 150 Display unit 160 storage unit 170 correction amount determination unit 180 correction unit

Claims (11)

An image forming apparatus configured to form images on both sides of a recording medium,
a photoreceptor drum; a charging device that charges the surface of the photoreceptor drum by applying a charging bias to the surface of the photoreceptor drum; an exposure device that exposes the photoreceptor drum to form a latent image; an image forming unit having a developing device that develops the latent image by adhering to it;
a storage unit for storing print history;
a correction amount determination unit that determines a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history;
a correction unit that corrects the bias value of the charging bias based on the correction amount;
with
The history of double-sided printing includes the number of double-sided prints and external environment information where double-sided printing was performed,
The image forming apparatus, wherein the correction amount determination unit determines the correction amount according to the most recent double-sided printing number and the environment information. The double-sided printing history includes a process speed during double-sided printing,
2. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient according to the process speed. The history of double-sided printing includes a fixing temperature during double-sided printing,
2. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient based on the fixing temperature. The history of double-sided printing includes the size of the recording medium for double-sided printing,
2. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient according to the size of the recording medium. The history of double-sided printing includes the elapsed time after double-sided printing,
2. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient corresponding to the elapsed time. The history of double-sided printing includes external environment information after double-sided printing,
2. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient according to the environment information. Equipped with a cooling fan inside the device,
The history of double-sided printing includes the operating state of the cooling fan from after double-sided printing to the next start of double-sided printing,
7. The image forming apparatus according to claim 1, wherein the correction amount determining unit multiplies the correction amount by a coefficient corresponding to an operating state of the cooling fan. . The history of double-sided printing includes the life of the photoreceptor drum during double-sided printing,
8. The image forming apparatus according to any one of claims 1 to 7, wherein the correction amount determination unit calculates the correction amount by multiplying the correction amount by a coefficient according to the life of the photosensitive drum. . When double-sided printing, which was continuously executed within a predetermined time in the past, was temporarily interrupted, and continuous printing was executed multiple times,
The correction amount determination unit calculates the correction amount for each continuous printing, and adds the calculated correction amounts to calculate the correction amount for the bias value of the charging bias. The image forming apparatus according to any one of claims 1 to 8. An image forming apparatus configured to form images on both sides of a recording medium,
a photoreceptor drum; a charging device that charges the surface of the photoreceptor drum by applying a charging bias to the surface of the photoreceptor drum; an exposure device that exposes the photoreceptor drum to form a latent image; an image forming unit having a developing device that develops the latent image by adhering to it;
a storage unit for storing print history;
a correction amount determination unit that determines a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history;
a correction unit that corrects the bias value of the charging bias based on the correction amount;
with
When double-sided printing, which was continuously executed within a predetermined time in the past, was temporarily interrupted, and continuous printing was executed multiple times,
The correction amount determination unit calculates the correction amount for each continuous printing, and adds the calculated correction amounts to calculate the correction amount of the bias value of the charging bias. forming device. A charging device control method for an image forming apparatus capable of forming images on both sides of a recording medium, comprising:
charging the surface of the photoreceptor drum by applying a charging bias to the surface of the photoreceptor drum;
exposing the photosensitive drum to form a latent image;
developing the latent image by applying toner;
a step of storing a print history;
a step of determining a correction amount of the bias value of the charging bias based on the history of double-sided printing in the printing history; and a step of correcting the bias value of the charging bias based on the correction amount;
with
The history of double-sided printing includes the number of double-sided prints and external environment information where double-sided printing was performed,
In the step of determining the correction amount, the charging bias control method is characterized in that the correction amount is determined according to the most recent double-sided printing number and the environmental information.

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