JP7225970B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In an electrophotographic image forming apparatus, there is known a technique for optimizing static elimination by measuring the surface potential of the photoreceptor before (or after) charging, and changing the location where the static elimination light is irradiated according to the measurement result. It is

As a technique of this kind, for example, Japanese Patent Laid-Open No. 2002-100003 discloses a technique for stabilizing image quality by uniformizing the surface potential of a photoreceptor even when the film thickness of the photoreceptor is thin. discloses a configuration in which static elimination is performed without irradiating static elimination light.

However, conventional static elimination methods require sensors (surface potential sensors, etc.) to be installed near the photoreceptor to measure the surface potential and film thickness of the photoreceptor, leading to increased costs and increased machine size. I had a problem with it.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to estimate the surface potential of a photoreceptor after static elimination at low cost and in a small space.

In order to solve the above-described problems, an image forming apparatus according to an aspect of the present invention includes an image carrier that carries an electrostatic latent image, a charging member that charges the image carrier, and a voltage applied to the charging member. and a control section for controlling the power supply, wherein the power supply superimposes a charging AC bias and a charging DC bias and applies them to the charging member to charge the image carrier during a printing operation. and when the printing operation is completed, only the charging AC bias is applied to the charging member to neutralize the surface of the image carrier, and the power source is the DC component of the current flowing from the power source to the image carrier. A certain charging DC current is detected and output to the control section, and the control section calculates the charging charge amount of the image carrier based on the information of the charging DC current received from the power supply, and the calculated charging charge. Based on the amount, the surface potential of the image carrier after static elimination is estimated, and the control unit controls the charging DC current for one round of the image carrier when the charging DC bias is started and when the charging DC bias is stopped. is calculated as the amount of charge during charging from the result of integration at start-up, and the amount of charge at the time of static elimination is calculated from the result of integration at the time of stop, and the amount of charge during charging and the amount of charge during static elimination are compared. When the amount of charge during static elimination falls below a certain percentage of the amount of charge during charging, it is determined that the static elimination has not been completed, and the static elimination sequence is extended.

It is possible to estimate the photoreceptor surface potential after static elimination at low cost and in a small space.

FIG. 1 is a diagram showing the overall configuration of an electrophotographic process of an image forming apparatus; Principal part configuration diagram of an image forming apparatus according to an embodiment Hardware configuration diagram of the control board FIG. 4 is a diagram showing temporal transitions of charging bias, charging current, and photoreceptor surface potential in the embodiment; A diagram for explaining the photoreceptor surface potential before and after charging. Graph showing time transition of charging bias, charging current, and photoreceptor surface potential when static elimination performance is degraded

Embodiments will be described below with reference to the accompanying drawings. In order to facilitate understanding of the description, the same constituent elements in each drawing are denoted by the same reference numerals as much as possible, and overlapping descriptions are omitted.

FIG. 1 is a diagram showing the overall configuration of an electrophotographic process of an image forming apparatus 1. As shown in FIG. FIG. 1 shows the electrophotographic process in general indirect transfer.

As shown in FIG. 1, in the electrophotographic process of the image forming apparatus 1, first, a high voltage generated by a high-voltage power supply 10 is applied to the charging roller 3 (charging member) to uniformly spread the photosensitive member 2 (image carrier). charged to After that, exposure is performed by the exposure unit 4 according to the image signal, and an electrostatic latent image is formed on the photosensitive member 2 . A toner image is developed by the developing device 5 , and the toner image on the photosensitive member 2 is transferred to the intermediate belt 7 by applying a high voltage generated by the high voltage power supply 11 to the primary transfer roller 6 . The toner image transferred to the intermediate transfer belt 7 is transferred to a recording material by a secondary transfer section, and then fixed by a fixing means to obtain an image. In addition, when the static eliminator 8 is provided, the static eliminator 8 removes the charge on the surface of the photoreceptor 2, and then the charging process is performed. In the case of color printing, there are four similar configurations, each of which transfers a toner image onto the intermediate transfer belt 7 for each color, and then reaches the secondary transfer section and fixing means.

FIG. 2 is a configuration diagram of the main parts of the image forming apparatus 1 according to the embodiment.

A high-voltage power supply 10 (power supply) is a device that generates a high voltage to be applied to the charging roller 3 . The high-voltage power supply 10 has a charging AC bias generator 12 and a charging DC bias generator 13, and generates a high voltage by superimposing a charging DC bias on a charging AC bias. A PWM (Pulse Width Modulation) signal, which is a control signal sent from the control board 9, determines the output magnitude and timing of the charging AC bias generator 12 and the charging DC bias generator 13. FIG. The charging AC bias and the charging DC bias are each controllable by control signals.

The high-voltage power supply 10 also has a charging DC current detection unit 14, which detects a DC component (charging DC current) of the current flowing from the charging roller 3 to the photosensitive member 2 and converts it into a signal. The charging DC current detection unit 14 outputs the value of the detected charging DC current to the control board 9 as a charging current FB signal.

The control board 9 (control unit) is a device that controls the high voltage power supply 10 and outputs a PWM signal, which is a control signal, to the high voltage power supply 10 . The control board 9 also calculates and processes the charging current FB signal from the charging DC current detection section 14 in the high voltage power supply 10 .

As shown in FIG. 2, the control board 9 includes a charge amount calculator 15, a surface potential estimator 16, a charge controller 17, a photoreceptor film thickness estimator 18, and a photoreceptor life determiner 19. have.

The charge amount calculation unit 15 calculates the charge amount of the photoreceptor 2 based on the charge current FB signal (charge DC current) received from the charge DC current detection unit 14 of the high voltage power supply 10 .

The surface potential estimator 16 estimates the surface potential of the photoreceptor 2 after static elimination based on the charging current FB signal received from the charging DC current detector 14 .

The charging control unit 17 adjusts the control signal to be output to the high-voltage power supply 10 based on the estimation result of the surface potential of the photoreceptor 2 after static elimination by the surface potential estimation unit 16 . Also, the charging control unit 17 adjusts the control signal to be output to the high-voltage power supply 10 based on information on the charge amount of the photoreceptor 2 calculated by the charge amount calculation unit 15 . Specifically, the charging control unit 17 sets the charge amount during static elimination calculated based on the information on the charging DC current during static elimination to a constant amount of the charge amount during charging computed based on the information on the charging DC current during static elimination. If it falls below the ratio, it is determined that the charge has not been completely removed, and the charge removal sequence is extended (delaying the stop timing of the charging AC bias). Further, the charging control unit 17 may be configured to stop the static elimination sequence when the duration of the static elimination sequence exceeds a predetermined threshold value. Further, the charging control section 17 may be configured to change the output of the charging DC bias in accordance with the film thickness estimated by the photoreceptor film thickness estimating section 18 .

The photoreceptor film thickness estimation unit 18 estimates the film thickness of the photoreceptor 2 based on the charging current FB signal (charging DC current) received from the charging DC current detection unit 14 .

The photoreceptor life determining unit 19 determines the life of the photoreceptor 2 according to the film thickness of the photoreceptor 2 estimated by the photoreceptor film thickness estimating unit 18 .

FIG. 3 is a hardware configuration diagram of the control board 9. As shown in FIG. As shown in FIG. 3, the control board 9 physically includes a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, a HDD (Hard Disk Drive) 104 and an I /F 105 can be configured as a computer system connected via a bus 106 . Also, an LCD (Liquid Crystal Display) 107 and an operation input unit 108 may be connected to the I/F 105 .

The CPU 101 is computing means and controls the overall operation of the control board 9 . The RAM 102 is a volatile storage medium from which information can be read and written at high speed, and is used as a working area when the CPU 101 processes information. The ROM 103 is a read-only non-volatile storage medium and stores programs such as firmware. The HDD 104 is a non-volatile storage medium from which information can be read and written, and stores an OS (Operating System), various control programs, application programs, and the like. The I/F 105 connects and controls the bus 106 and various hardware and networks. LCD 107 is a visual user interface for the user to check the status. The operation input unit 108 is a user interface such as a keyboard and a mouse for the user to input information.

The function of each element of the control board 9 shown in FIG. and operate the LCD 107 , the operation input unit 108 , and the external device via the I/F 105 .

4 to 6, the relationship between the charging AC bias and the charging DC bias applied to the charging roller 3, the charging DC current, and the photosensitive member surface potential in this embodiment will be described. FIG. 4 is a diagram showing temporal transitions of charging bias, charging current, and photoreceptor surface potential in the embodiment. The horizontal axis in FIG. 4 represents time. The example shown in FIG. 4 shows the temporal transition of each parameter in a state in which the static elimination performance of the photoreceptor 2 has not deteriorated.

The surface potential of the photoreceptor 2 is charged so as to follow the charging DC bias. When the photoreceptor 2 is charged, a charging DC current flows from the high voltage power supply 10, and the relationship can be expressed by the following equation (1).

ここで、Ｉ_ｄｃは帯電ＤＣ電流、εは感光体２の誘電率、λはプロセス速度、Ｌは感光体２の帯電領域長手方向長さ、ｄは感光体２の膜厚、Ｖ_ｄは帯電後の感光体２の表面電位、Ｖ_ｄ０は帯電前の感光体２の表面電位である。

Here, _Idc is the charging DC current, ε is the dielectric constant of the photoreceptor 2, λ is the process speed, L is the longitudinal length of the charged area of the photoreceptor 2, d is the film thickness of the photoreceptor 2, and _Vd is the charging The surface potential of the photoreceptor 2 afterward, _Vd0 , is the surface potential of the photoreceptor 2 before charging.

FIG. 5 is a diagram for explaining the photoreceptor surface potential before and after charging. As shown in FIG. 5, the surface potential on the upstream side of the contact position with the charging roller 3 in the rotation direction of the photoreceptor 2 is the pre-charged photoreceptor surface potential _Vd0 , and the surface potential on the downstream side of the contact position with the charging roller 3 is Vd0. The surface potential on the side is the post-charging photoreceptor surface potential _Vd . The photoreceptor surface potential _Vd0 before charging is also the photoreceptor surface potential after static elimination.

As shown in FIG. 4, when the charging DC bias is started at time t1, the bias is applied to the photoreceptor 2 whose photoreceptor surface potential _Vd0 before charging is 0 (V). A charging DC current is generated at . In the case of a system without static elimination, the already charged photoreceptor 2 is in contact with the charging roller 3 (V _d0 =V _d ) after the second rotation of the photoreceptor 2 after time t2, so that no charging DC current is generated.

After the charging DC bias is stopped after time t3, when only the charging AC bias is applied, the photoreceptor 2 charged to V _d0 =V _d is neutralized (V _d =0), and as shown in region B in the figure, the charge is reversed. A charging current of polarity flows. In this embodiment, the charging DC current detection section 14 has a positive charging DC current detection section and a negative charging DC current detection section so that the charging current of opposite polarity can be detected.

When charging DC bias is started at time t1 and when charging DC bias is stopped at time t3, the charging DC current for one round of the photosensitive member 2 is integrated, and the integration result A (charge amount at the time of charging) at start and stop It compares with the integration result B (charge amount at the time of static elimination). If the charge is sufficiently removed, as shown in FIG. 4, the amount of charge B at the time of charge removal is equal to the charge amount A at the time of charge (A=B). can be detected.

FIG. 6 is a graph showing temporal transitions of the charging bias, charging current, and photoreceptor surface potential in a state where the static elimination performance is deteriorated. The specifications of FIG. 6 are the same as those of FIG.

If the static elimination performance is sufficient, as described with reference to FIG. 4, the charge amount B during static elimination for one rotation of the photosensitive member is the same as the charge amount A during charging (A=B), but deterioration over time occurs. If the static elimination performance deteriorates due to environmental fluctuations, the charge amount B during static elimination becomes smaller than the charge amount A during charging (A>B), as shown in FIG. In this case, the static elimination sequence (static elimination time) is extended until the total amount B' of the charge amount during static elimination becomes the same as the charge amount A during charging for one rotation of the photosensitive member (A=B'). can stabilize the surface potential of the photoreceptor.

In the example of FIG. 6, after the charge removal for one round of the photoreceptor 2 is performed from time t3 to t4, another charge removal sequence is added at time t4 to t5 (that is, the charging AC bias stop timing is set at time t4 to t5). extended from t4 to time t5). Let C be the amount of charge corresponding to the extension of the static elimination time. Due to the negative charging DC current for the extension of the static elimination time, the total charge amount B' during static elimination increases from B to B+C, and the relationship of A=B' is established, and the static elimination of the photoreceptor 2 is completed at time t5. are doing.

If these processes are applied to the functions of the control board 9 illustrated in FIG. 2, for example, the charge amount calculator 15 shown in FIG. A charge amount A at the time and a charge amount B at the time of static elimination are calculated. The charge control unit 17 compares the charge amount A during charging and the charge amount B during neutralization calculated by the charge amount calculation unit 15 . When the charge amount B during static elimination falls below a certain percentage of the charge amount A during charging, it is determined that the photosensitive member 2 has not been completely eliminated, and the static elimination sequence is extended (i.e., the charging AC bias is stopped). A control signal for extending the timing is transmitted to the charging AC bias generator 12 .

These configurations can stabilize the photoreceptor surface potential after static elimination. If the surface potential of the photoreceptor after static elimination can be stabilized, the charging AC bias application time can be shortened rather than determining the static elimination time according to the worst conditions. .

The charging control unit 17 may be configured to stop the static elimination sequence when the duration of the static elimination sequence exceeds a predetermined threshold. As a result, it is possible to prevent the static elimination time from becoming extremely long, and even if the static elimination does not fall within the allowable range due to some trouble, the static elimination process can be forcibly terminated. Performance can be improved.

Further, the relationship between the charging DC current _Idc and the surface potential _Vd0 of the photoreceptor after static elimination (before charging) can be expressed by the above equation (1). 9, the photoreceptor surface potential after static elimination can be estimated using equation (1). When applied to the functions of the control board 9 illustrated in FIG. 2, for example, the surface potential estimation unit 16 shown in _FIG . (1) is used to calculate the photoreceptor surface potential _Vd0 after static elimination. The charge control unit 17 controls the charge AC bias generation unit 12 and the charge DC bias generation unit 12 so as to change, for example, the locations irradiated with the charge-removing light, according to the photoreceptor surface potential _Vd0 after charge removal estimated by the surface potential estimation unit 16. 13 to adjust the control signal to be transmitted to the photoreceptor 2, thereby optimizing the static elimination of the photoreceptor 2. FIG.

With these configurations, the surface potential of the photoconductor 2 can be estimated from the charging DC current without directly measuring it, so there is no need to install sensors for measuring the surface potential near the photoconductor 2. , the photoreceptor surface potential after static elimination can be estimated at low cost and in a small space.

Further, in the present embodiment, the photoreceptor film thickness estimator 18 preferably estimates the film thickness of the photoreceptor 2 using the detection result of the charging DC current. The photoreceptor film thickness estimating unit 18 receives the input from the charging DC current detecting unit 14 in the same manner as the method of calculating the film thickness based on the measured value of the current value on the surface of the photoreceptor 2 described in Patent Document 1, for example. Using the charging current FB signal (charging DC current I _dc ), the film thickness of the photoreceptor 2 can be estimated by a calculation method similar to that of Patent Document 1. With this configuration, the film thickness of the photoreceptor 2 can be estimated inexpensively and in a small space by using the charging DC current without installing an ammeter near the photoreceptor 2 as in Patent Document 1. .

Further, in this embodiment, it is preferable that the photoreceptor life determination unit 19 determines the life of the photoreceptor 2 according to the film thickness of the photoreceptor 2 estimated by the photoreceptor film thickness estimation unit 18 . For example, the photoreceptor life determination unit 19 can determine that the wear of the photoreceptor progresses as the estimated film thickness decreases, and the life can be determined to be short. With this configuration, the life of the photoreceptor 2 can be determined inexpensively and in a small space.

Further, in the present embodiment, the charging control section 17 preferably outputs a charging DC bias according to the film thickness of the photoreceptor 2 estimated by the photoreceptor film thickness estimating section 18 . Accordingly, it is possible to adjust the charging DC bias in accordance with the film thickness, suppress film thickness consumption, and extend the life of the photoreceptor 2 .

The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples by those skilled in the art are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each specific example described above and its arrangement, conditions, shape, etc. are not limited to those illustrated and can be changed as appropriate. As long as there is no technical contradiction, the combination of the elements included in the specific examples described above can be changed as appropriate.

1 image forming apparatus 2 photoreceptor (image carrier)
3 charging roller (charging member)
9 Control board (control unit)
10 high voltage power supply (power supply)
12 Charging AC bias generation section 13 Charging DC bias generation section 14 Charging DC current detection section 15 Charge amount calculation section 16 Surface potential estimation section 17 Charge control section 18 Photoreceptor film thickness estimation section 19 Photoreceptor life determination section I _dc charging DC current

JP 2015-230450 A

Claims (6)

an image carrier that carries an electrostatic latent image;
a charging member that charges the image carrier;
a power supply that applies a voltage to the charging member;
a control unit that controls the power supply;
with
The power source applies a superimposed charging AC bias and a charging DC bias to the charging member during a printing operation to charge the image carrier, and applies only the charging AC bias to the charging member at the end of the printing operation. to remove the charge from the surface of the image carrier by applying
the power supply detects a charging DC current, which is a DC component of the current flowing from the power supply to the image carrier, and outputs the charging DC current to the control unit;
The control unit calculates the charge amount of the image carrier based on the charging DC current information received from the power supply, and estimates the surface potential of the image carrier after charge removal based on the calculated charge amount. death,
The control unit
When the charging DC bias is started and when the charging DC bias is stopped, the charging DC current for one round of the image bearing member is integrated, and the integration result at the start is calculated as the charge amount at the time of charging. Calculate the integration result as the amount of charge during static elimination,
The charge amount during charging and the charge amount during static elimination are compared, and if the charge amount during static elimination is less than a certain ratio of the charge amount during static elimination, it is determined that static elimination has not been completed. , to extend the neutralization sequence,
Image forming device. The power supply has a positive charging DC current detection unit and a negative charging DC current detection unit,
The image forming apparatus according to claim 1. The control unit stops the static elimination sequence when the duration of the static elimination sequence exceeds a predetermined threshold.
The image forming apparatus according to claim 1 . The control unit estimates the film thickness of the image carrier using the detection result of the charging DC current.
The image forming apparatus according to any one of claims 1 to 3 . The control unit determines the life of the image carrier according to the estimated film thickness.
The image forming apparatus according to claim 4 . The control unit outputs the charging DC bias according to the estimated film thickness.
The image forming apparatus according to claim 4 or 5 .

Images