JP6988340B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In an image forming apparatus such as an electrophotographic printer, an image is formed on paper by using an image forming process including each step of charging, exposure, development, transfer, and fixing.

In the charging step, from the viewpoint of environmental protection, as a charging member for charging the surface of the photoconductor drum, a charging roller that discharges to the photoconductor drum while rotating in contact with or close to the photoconductor drum is used. A superposed voltage in which a DC voltage and an AC voltage are superimposed is applied to the charging roller in order to uniformly charge the surface of the photoconductor drum (for example, Patent Document 1). The inter-peak voltage of the AC component (AC voltage) of the superimposed voltage is adjusted to an appropriate value so that the charging roller does not excessively discharge the photoconductor drum.

Japanese Unexamined Patent Publication No. 2008-1605015

By the way, when a superposed voltage is applied to the charging roller, the temperature of the charging roller rises due to Joule heat. When the temperature of the charging roller rises, the impedance of the elastic layer of the charging roller decreases, and the discharge current flowing through the charging roller increases.

Therefore, if the image forming apparatus continuously performs the image forming operation after adjusting the peak voltage of the AC component of the superimposed voltage, the temperature of the charging roller rises and the charging roller causes an excessive discharge to the photoconductor drum. Will do. As a result, there is a problem that the deterioration of the photoconductor drum is promoted and the life of the photoconductor drum is shortened.

If the peak-to-peak voltage of the AC component of the superimposed voltage is frequently adjusted, excessive discharge of the charging roller can be prevented and deterioration of the photoconductor drum can be suppressed. However, since it takes time to adjust the peak voltage, it is not preferable to frequently adjust the peak voltage because the productivity of the image forming apparatus is lowered.

The present invention has been made in view of the above-mentioned problems. Therefore, an object of the present invention is a photoconductor while maintaining high productivity even in a configuration in which a superposed voltage obtained by superimposing a DC voltage and an AC voltage is applied to a charging roller to charge the surface of the photoconductor drum. The purpose of the present invention is to provide an image forming apparatus capable of extending the life of a drum.

The above object of the present invention is achieved by the following means.

(1) The charging member that contacts or rotates in close contact with or close to the image carrier and discharges to the image carrier to charge the surface of the image carrier, and the superimposed voltage obtained by superimposing the DC voltage and the AC voltage are charged. A power supply applied to the member, a surface electrometer for measuring the surface potential of the image carrier, and a surface electrometer.
It has an in-flight temperature sensor that detects the in-flight temperature inside the device and a control unit that adjusts the peak-to-peak voltage of the AC voltage, and the control unit raises the temperature of the charging member to a predetermined temperature or higher. , The peak voltage is adjusted , and the adjusted adjustment value is set as the output at the time of image formation.
The predetermined temperature is a temperature higher than the in-flight temperature determined according to the in-flight temperature detected by the in-flight temperature sensor, and the adjustment of the peak voltage by the control unit is performed by the surface electrometer. An image forming apparatus performed by detecting the surface potential of the image carrier.
(2) A charging member that comes into contact with or rotates close to the image carrier and discharges to the image carrier to charge the surface of the image carrier.
A power supply that applies a superposed voltage that superimposes a DC voltage and an AC voltage to the charging member, and
An in-flight temperature sensor that detects the in-flight temperature inside the device,
It has a control unit that adjusts the peak-to-peak voltage of the AC voltage, and has.
The control unit adjusts the peak voltage after raising the temperature of the charging member to a predetermined temperature or higher, and sets the adjusted adjustment value as the output at the time of image formation.
The predetermined temperature is a temperature higher than the in-flight temperature determined according to the in-flight temperature detected by the in-flight temperature sensor.
The adjustment of the peak voltage by the control unit is performed by detecting the current value of the current flowing from the power supply to the charging member.
Image forming device.
(3) The control unit adjusts the peak voltage when the number of prints of the print job is equal to or more than a predetermined number, and executes the print job using the adjusted adjustment value (1). , Or the image forming apparatus according to (2) above.

( 4 ) The control unit raises the temperature of the charging member by performing a preliminary drive, which is an operation of rotating the charging member and the image carrier while applying the superimposed voltage to the charging member by the power supply. The image forming apparatus according to any one of (1) to (3) above.

( 5 ) The image forming apparatus according to (4 ) above, wherein when the pre-driving is performed, the control unit increases the frequency of the AC voltage from the time of normal image forming.

( 6 ) The image forming apparatus according to (4 ) or ( 5 ) above, wherein when the pre-driving is performed, the control unit increases the DC voltage as compared with the case of normal image forming.

( 7 ) The above-mentioned one of (4 ) to ( 6 ), wherein when the preliminary drive is performed, the control unit increases the inter-peak voltage of the AC voltage from the time of normal image formation. Image forming device.

( 8 ) The image forming apparatus according to any one of (4 ) to ( 7 ) above, wherein the control unit determines whether or not to perform the preliminary drive based on the temperature of the charging member.

( 9 ) The image forming apparatus according to any one of (4 ) to ( 8 ) above, wherein the control unit continues the preliminary drive until the temperature of the charging member reaches the predetermined temperature.

( 10 ) The image forming apparatus according to (8 ) or ( 9 ) above, wherein the control unit detects the temperature of the charged member by detecting the current value of the current flowing from the power source to the charged member.

According to the present invention, since the peak voltage is adjusted after the temperature of the charging member is raised, the temperature of the charging member does not rise significantly even if the image forming operation is continuously performed after the peak voltage is adjusted. , It is prevented that the charged member discharges excessively. Therefore, deterioration of the photoconductor drum can be suppressed without frequently adjusting the peak voltage. That is, the life of the photoconductor drum can be extended while maintaining high productivity.

It is sectional drawing which shows the schematic structure of the image forming apparatus which concerns on one Embodiment of this invention. It is a figure which shows the schematic structure of the charging device. It is a flowchart which shows the procedure of a print job execution process. It is a figure which shows the relationship between the temperature of a charging roller and a discharge current. It is a figure for demonstrating the charging characteristic of a photoconductor drum. It is a figure which shows the relationship between the frequency of superimposition voltage, and the rate of temperature rise of a charge roller.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 includes a control unit 10, a storage unit 20, an operation panel unit 30, an image forming unit 40, a fixing unit 50, and a paper feeding unit 60.

The control unit 10 is a CPU (Central Processing Unit), and controls each of the above units and performs various arithmetic processes according to a program.

The storage unit 20 stores a ROM (Read Only Memory) for storing various programs and various data in advance, a RAM (Random Access Memory) for temporarily storing programs and data as a work area, and various programs and various data. It consists of a hard disk and the like. The storage unit 20 stores a conversion table that correlates the temperature of the charging roller 422a (see FIG. 2) with the current value of the current flowing through the charging roller 422a.

The operation panel unit 30 includes a touch panel, a numeric keypad, a start button, a stop button, and the like, and is used for displaying various information and inputting various instructions.

The image forming unit 40 forms an image based on various data on the paper 100 by using an electrophotographic process. A transfer belt 41 is arranged at the center of the image forming portion 40. The transfer belt 41 is rotationally driven in the direction of arrow A.

On the side surface of the transfer belt 41, four image forming units 42Y, 42M, 42C, and 42K are arranged in the order of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 42Y to 42K have a similar configuration. For convenience of illustration and description, in FIG. 1, the reference numerals are given only to the components of the image formation unit 42Y, and the reference numerals are omitted for the other components of the image formation units 42M to 42K.

Each image forming unit 42Y to 42K has a photoconductor drum 421 as an image carrier. A charging device 422, an exposure device 423, a developing device 424, a lubricant supply device 425, a photoconductor cleaner 426, and an eraser 427 are arranged around each photoconductor drum 421. The charging device 422 uniformly charges the surface of the photoconductor drum 421. The exposure apparatus 423 forms an electrostatic latent image according to the image data on the surface of the uniformly charged photoconductor drum 421. The developing device 424 develops the electrostatic latent image into a toner image. The lubricant supply device 425 supplies the lubricant to the surface of the photoconductor drum 421. The photoconductor cleaner 426 removes the toner on the photoconductor drum 421. The eraser 427 eliminates static electricity on the surface of the photoconductor drum 421.

Further, primary transfer rollers 43Y, 43M, 43C, 43K are arranged at positions facing each photoconductor drum 421 with the transfer belt 41 interposed therebetween. The primary transfer rollers 43Y to 43K electrostatically attract the toner image formed on the surface of the photoconductor drum 421 and perform the primary transfer onto the transfer belt 41.

A secondary transfer roller 44 is arranged at the end of the transfer belt 41. The secondary transfer roller 44 secondarily transfers the toner image formed on the transfer belt 41 to the conveyed paper 100. When performing the secondary transfer, a high-voltage positive transfer voltage is applied to the secondary transfer roller 44 to electrostatically attract the negatively charged toner image to the paper 100. The paper 100 on which the toner image is transferred is supplied to the fixing unit 50.

The fixing unit 50 heats and pressurizes the toner image transferred onto the paper 100 with a fixing roller to fix the toner image on the paper 100.

The paper feed unit 60 accommodates the paper 100 used for printing. A paper feed cassette is detachably provided on the paper feed unit 60.

Next, with reference to FIG. 2, the charging device 422 of the present embodiment will be described more specifically.

FIG. 2 is a diagram showing a schematic configuration of a charging device 422 of the image forming unit 42Y. Since the charging devices 422 of the image forming units 42Y to 42K have the same configuration as each other, the charging device 422 of the image forming unit 42Y will be described below as a representative.

The charging device 422 includes a charging roller 422a that discharges to the photoconductor drum 421 while rotating in contact with or close to the photoconductor drum 421, and a power supply 422b that applies a voltage to the charging roller 422a.

The charging roller 422a has a structure in which a conductive elastic layer is formed on the outer periphery of the conductive core metal. The conductive elastic layer contains, for example, epichlorohydrin rubber, which is a crosslinked rubber, as a main component and contains an ionic conductive agent. For example, a protective layer containing nylon resin as a main component may be formed on the outer periphery of the conductive elastic layer.

The power supply 422b is composed of a DC power supply 451 that generates a DC voltage and an AC power supply 452 that generates an AC voltage. The power supply 422b applies a superposed voltage obtained by superimposing a DC voltage and an AC voltage to the charging roller 422a. The DC power supply 451 is a variable power supply, and the voltage value of the DC voltage is changed by the control unit 10. The AC power supply 452 is a variable power supply, and the frequency of the AC voltage or the voltage value of the peak voltage is changed by the control unit 10. The DC voltage has the same polarity as the charging polarity of the toner.

A current sensor 453 is provided between the charging roller 422a and the power supply 422b. The current sensor 453 detects the current value of the current flowing from the power supply 422b to the charging roller 422a. The current value detected by the current sensor 453 is transmitted to the control unit 10. Further, a surface electrometer 454 is provided near the surface of the photoconductor drum 421. The surface electrometer 454 detects the surface potential of the photoconductor drum 421. The surface potential detected by the surface electrometer 454 is transmitted to the control unit 10.

The image forming apparatus 1 may include components other than the above-mentioned components, or may not include some of the above-mentioned components.

In the image forming apparatus 1 configured as described above, for example, when printing based on a print job, the peak of the AC component of the superimposed voltage applied to the charging roller 422a in order to prevent excessive discharge of the charging roller 422a. The inter-voltage (hereinafter, also referred to as "AC peak-to-peak voltage") is adjusted. Hereinafter, the operation of the image forming apparatus 1 for adjusting the AC peak voltage of the superimposed voltage will be described in detail with reference to FIGS. 3 to 6.

FIG. 3 is a flowchart showing a procedure of print job execution processing executed by the image forming apparatus 1. The algorithm shown by the flowchart of FIG. 3 is stored as a program in the storage unit 20 of the image forming apparatus 1, and is executed by the control unit 10. Further, in the following, a case of adjusting the AC peak voltage of the superimposed voltage applied to the charging roller 422a of the image forming unit 42Y will be described as an example.

First, the image forming apparatus 1 starts pre-driving the photoconductor drum 421 and the charging roller 422a (step S101). More specifically, the control unit 10 of the image forming apparatus 1 controls the power supply 422b and applies a superposed voltage to the charging roller 422a under normal driving conditions during image forming, while the photoconductor drum 421 and the charging roller. 422a is rotated in a predetermined rotation direction.

Next, the image forming apparatus 1 detects the temperature of the charging roller 422a (step S102). In the present embodiment, the control unit 10 of the image forming apparatus 1 first acquires the output value of the current sensor 453, and for example, by integrating the output value, it flows from the power supply 422b to the charging roller 422a for a certain period of time. Calculate the current value of the current. Then, the control unit 10 refers to the conversion table stored in the storage unit 20 and detects the temperature of the charging roller 422a from the current value of the charging roller 422a.

Next, the image forming apparatus 1 determines whether or not the temperature of the charging roller 422a is lower than the predetermined temperature (step S103). Here, the predetermined temperature is a value that serves as a reference when determining whether or not to adjust the AC peak voltage of the superimposed voltage. For example, as shown in Table 1 below, the in-flight temperature sensor of the image forming apparatus 1 (Not shown) is determined according to the detected in-flight temperature.

When it is determined that the temperature of the charging roller 422a is equal to or higher than the predetermined temperature (step S103: NO), the image forming apparatus 1 moves to the process of step S111.

On the other hand, when it is determined that the temperature of the charging roller 422a is lower than the predetermined temperature (step S103: YES), the image forming apparatus 1 analyzes the print job and determines whether or not the number of printed sheets is the predetermined number or more. (Step S104). Here, the predetermined number of sheets is a value that serves as a reference when determining whether or not to adjust the AC peak voltage of the superimposed voltage, and is determined in consideration of the printing speed of the image forming apparatus 1 and the like. The predetermined number of sheets is set to, for example, 100 sheets.

When it is determined that the number of printed sheets is less than the predetermined number (step S104: NO), the image forming apparatus 1 moves to the process of step S111.

On the other hand, when it is determined that the number of printed sheets is a predetermined number or more (step S104: YES), the image forming apparatus 1 increases the frequency of the superimposed voltage applied to the charging roller 422a (step S105). More specifically, the control unit 10 of the image forming apparatus 1 controls the AC power supply 452 to increase the frequency of the AC component of the superimposed voltage applied to the charging roller 422a from the frequency at the time of normal image forming. Let me.

Next, the image forming apparatus 1 detects the temperature of the charging roller 422a (step S106). In the present embodiment, the control unit 10 of the image forming apparatus 1 detects the temperature of the charging roller 422a from the current value of the charging roller 422a, as in the process shown in step S102.

Next, the image forming apparatus 1 determines whether or not the temperature of the charging roller 422a is equal to or higher than a predetermined temperature (step S107).

When it is determined that the temperature of the charging roller 422a is lower than the predetermined temperature (step S107: NO), the image forming apparatus 1 returns to the process of step S106. Then, the image forming apparatus 1 repeats the process of step S106 or less until the temperature of the charging roller 422a becomes equal to or higher than the predetermined temperature.

On the other hand, when it is determined that the temperature of the charging roller 422a is equal to or higher than a predetermined temperature (step S107: YES), the image forming apparatus 1 reduces the frequency of the superimposed voltage applied to the charging roller 422a (step S108). More specifically, the control unit 10 of the image forming apparatus 1 controls the AC power supply 452 to return the frequency of the AC component of the superimposed voltage applied to the charging roller 422a to the frequency at the time of normal image formation.

Next, the image forming apparatus 1 adjusts the AC peak voltage of the superimposed voltage (step S109). In the present embodiment, the control unit 10 of the image forming apparatus 1 first swings the AC peak voltage while measuring the surface potential of the photoconductor drum 421, and the surface potential does not increase even if the AC peak voltage increases. Recognize the saturation point. Then, the control unit 10 sets a value obtained by adding a predetermined amount to the AC peak voltage (AC discharge start voltage) at the saturation point as the AC peak voltage at the time of image formation.

Then, the image forming apparatus 1 performs an image forming process (step S110), and ends the process. More specifically, the control unit 10 of the image forming apparatus 1 controls the image forming unit 40 to perform printing based on the print job while applying the adjusted AC peak voltage, and ends the process.

As described above, according to the process shown in steps S101 to S110 of FIG. 3, when the temperature of the charging roller 422a is lower than the predetermined temperature and the number of printed sheets is the predetermined number or more, the superimposed voltage applied to the charging roller 422a. The frequency of the charging roller 422a is increased, and the temperature of the charging roller 422a is raised to a predetermined temperature. After that, the AC peak voltage of the superimposed voltage applied to the charging roller 422a is adjusted, and the image forming process is performed.

On the other hand, when the temperature of the charging roller is equal to or higher than the predetermined temperature (step S103: NO), or when the number of printed sheets is less than the predetermined number (step S104: NO), the image forming apparatus 1 adjusts the AC peak voltage. The necessity determination process for determining the necessity of the above is performed (step S111). More specifically, the control unit 10 of the image forming apparatus 1 determines whether or not the AC peak voltage needs to be adjusted with reference to the operation history of the image forming apparatus 1. For example, in the case of the first printing after the power supply of the image forming apparatus 1 is turned on, the control unit 10 determines that the AC peak voltage needs to be adjusted.

Next, the image forming apparatus 1 determines whether or not the AC peak voltage needs to be adjusted based on the result of the necessity determination process shown in step S111 (step S112).

When it is determined that the adjustment of the AC peak voltage is not necessary (step S112: NO), the image forming apparatus 1 applies the AC peak voltage at the time of normal image formation to perform the image forming process (step S110). , End the process.

On the other hand, when it is determined that the AC peak voltage needs to be adjusted (step S112: YES), the image forming apparatus 1 adjusts the AC peak voltage (step S109). Then, the image forming apparatus 1 applies the adjusted AC peak voltage to perform an image forming process (step S110), and ends the process.

As described above, according to the process of the flowchart shown in FIG. 3, when the temperature of the charging roller 422a is detected, the temperature of the charging roller 422a is less than the predetermined temperature, and the number of printed sheets is the predetermined number or more, the temperature of the charging roller 422a. Is raised to a predetermined temperature. After that, the AC peak voltage of the superimposed voltage applied to the charging roller 422a is adjusted, and printing is performed by applying the adjusted AC peak voltage. On the other hand, when the temperature of the charging roller 422a is equal to or higher than the predetermined temperature or the number of printed sheets is less than the predetermined number, the AC peak voltage is adjusted as necessary and printing is performed.

As described above, according to the image forming apparatus 1 of the present embodiment, after raising the temperature of the charging roller 422a to a predetermined temperature, the AC peak voltage of the superimposed voltage is adjusted. According to such a configuration, even if the image forming operation is continuously performed after adjusting the AC peak voltage, the temperature of the charging roller 422a does not rise significantly, and the charging roller 422a with respect to the photoconductor drum 421. Excessive discharge is prevented. Therefore, deterioration of the photoconductor drum can be suppressed without frequently adjusting the AC peak voltage of the superimposed voltage. That is, the life of the photoconductor drum 421 can be extended while maintaining the high productivity of the image forming apparatus 1.

Further, according to the image forming apparatus 1 of the present embodiment, when the charging roller 422a is preliminarily driven to raise the temperature of the charging roller 422a, the frequency of the superimposed voltage applied to the charging roller 422a is increased. According to such a configuration, the time required for raising the temperature of the charging roller 422a can be shortened as compared with the case where the charging roller 422a is preliminarily driven without increasing the frequency of the superimposed voltage.

Next, with reference to FIGS. 4 to 6, the operation and effect of the image forming apparatus 1 according to the present embodiment will be described more specifically.

FIG. 4 is a diagram showing the relationship between the temperature of the charging roller and the discharge current. The vertical axis of FIG. 4 shows the current value (integral value) of the discharge current flowing through the charging roller 422a when a predetermined superimposed voltage is applied, and the horizontal axis shows the temperature of the charging roller 422a.

As described above, when the temperature of the charging roller 422a rises, the impedance of the conductive elastic layer of the charging roller 422a decreases. Therefore, as shown in FIG. 4, when a predetermined superimposed voltage is applied to the charging roller 422a, the discharge current value of the charging roller 422a increases as the temperature of the charging roller 422a increases.

Therefore, in a configuration in which a superposed voltage is applied to the charging roller 422a to charge the surface of the photoconductor drum 421, the surface of the photoconductor drum 421 is desired to have a smaller AC peak voltage as the temperature of the charging roller 422a is higher. It is charged to the surface potential of.

FIG. 5 is a diagram for explaining the charging characteristics of the photoconductor drum with respect to the AC peak voltage. The vertical axis of FIG. 5 shows the surface potential of the photoconductor drum when the surface of the photoconductor drum is charged by applying the superposed voltage to the charging roller, and the horizontal axis shows the AC peak voltage of the superposed voltage. The broken line in FIG. 5 shows the charging characteristics when the temperature of the charging roller is the first temperature, and the solid line shows the charging characteristics when the temperature of the charging roller is higher than the first temperature at the second temperature.

As shown in FIG. 5, the surface potential of the photoconductor drum 421 increases as the AC peak voltage increases until the AC discharge occurs, and does not change even if the AC peak voltage increases when the AC discharge occurs.

Then, as described above, the surface of the photoconductor drum 421 is charged to a desired surface potential with a smaller AC peak voltage as the temperature of the charging roller 422a is higher. In other words, as shown by the arrow in FIG. 5, the charging characteristic of the photoconductor drum 421 with respect to the AC peak voltage shifts to the lower voltage side as the temperature of the charging roller 422a increases.

Therefore, in a general image forming apparatus that adjusts the AC peak voltage without raising the temperature of the charging roller, if the image forming operation is continuously performed after adjusting the AC peak voltage, the temperature of the charging roller rises. Then, the charging roller causes an excessive discharge to the photoconductor drum. As a result, in a general image forming apparatus, deterioration of the photoconductor drum is promoted due to excessive discharge of the charging roller.

On the other hand, in the image forming apparatus 1 of the present embodiment, since the AC peak voltage is adjusted after the temperature of the charging roller 422a is increased, the temperature of the charging roller 422a is greatly increased even if the image forming operation is continuously performed. This prevents the charging roller 422a from excessively discharging. Therefore, according to the image forming apparatus 1 of the present embodiment, deterioration of the photoconductor drum 421 due to excessive discharge of the charging roller is suppressed. In the image forming apparatus 1 of the present embodiment, deterioration of the photoconductor drum 421 can be remarkably suppressed, especially when the power of the charging roller 422a is first turned on in the morning or in a low temperature environment.

Next, with reference to FIG. 6, the relationship between the frequency of the superimposed voltage applied to the charging roller 422a and the temperature rising rate of the charging roller 422a will be described.

FIG. 6 is a diagram showing the relationship between the frequency of the superimposed voltage and the rate of temperature rise of the charging roller. The vertical axis of FIG. 6 shows the amount of temperature rise when the superimposed voltage is applied to the charging roller for a predetermined time, and the horizontal axis shows the frequency of the AC component of the superimposed voltage.

As shown in FIG. 6, when a superposed voltage is applied to the charging roller 422a, the higher the frequency of the AC component, the larger the amount of temperature rise of the charging roller 422a. This phenomenon is caused by the fact that the higher the frequency of the AC component of the superimposed voltage applied to the charging roller 422a, the lower the impedance of the capacitor component of the charging roller 422a and the higher the current flowing through the charging roller 422a. Therefore, according to the image forming apparatus 1 of the present embodiment, when the temperature of the charging roller 422a is raised, the influence on the deterioration of the photoconductor drum 421 is minimized by increasing the frequency of the AC component of the superimposed voltage. However, the time required for raising the temperature of the charging roller 422a can be shortened.

Unlike the present embodiment, when the superimposed voltage is applied to the charging roller 422a, the voltage value of the AC peak voltage is increased or the voltage value of the DC component is increased to raise the temperature of the charging roller 422a. The time required for this may be shortened. When the AC peak voltage or the voltage value of the DC component is increased, the effect on the deterioration of the photoconductor drum 421 is greater than when the frequency is increased, but the effect is when the image forming operation is continuously performed. It is extremely small compared to the influence of over-discharge due to the temperature rise of the charging roller 422a.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims.

For example, in the above-described embodiment, the AC peak voltage of the superimposed voltage is obtained by measuring the surface potential of the photoconductor drum 421, shaking the AC peak voltage, and detecting the saturation point at which the surface potential is saturated. .. However, the AC peak voltage may be obtained by shaking the AC peak voltage while measuring the current value of the current flowing through the charging roller 422a and detecting the point where the current value changes characteristically.

Further, in the above-described embodiment, the temperature of the charging roller 422a is detected by measuring the current value of the current flowing through the charging roller 422a. However, the temperature of the charging roller 422a may be directly detected by using a non-contact temperature sensor such as a thermopile sensor or a thermistor.

Further, in the above-described embodiment, the temperature of the charging roller 422a is detected, and by comparing the temperature of the charging roller 422a with a predetermined temperature, it is determined whether or not to predrive the charging roller 422a and the photoconductor drum 421. rice field. However, whether or not to predrive the charging roller 422a and the photoconductor drum 421 may be determined based on the in-flight temperature of the image forming apparatus 1, or the operation history of the image forming apparatus 1 (for example, the previous operation history). It may be determined based on whether or not the elapsed time from the end of printing is less than or equal to a predetermined time).

Further, in the above-described embodiment, the case where the surface of the photoconductor drum 421 is charged by the charging roller 422a has been described as an example. However, the charging member that charges the surface of the photoconductor drum 421 is not limited to the charging roller 422a, and the charging brush that discharges to the photoconductor drum 421 while rotating in contact with or close to the photoconductor drum 421. May be.

The means and methods for performing various processes in the image forming apparatus according to the above-described embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a CD-ROM (Compact Disk Read Only Memory), or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. Further, the above program may be provided as a single application software, or may be incorporated into the software of the device as a function of the image forming device.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to this embodiment.

(Example 1)
Using a modified machine of a commercially available image forming apparatus (bizhub PRESS C1100 manufactured by Konica Minolta Co., Ltd.) having the same image forming unit as the above-described embodiment, printing was performed in units of 5000 sheets while adjusting the AC peak voltage. ..

Specifically, first, under an environment of a temperature of 10 ° C. and a humidity of 20%, the driving conditions during normal image formation (frequency of AC component of superimposed voltage: 3 KHz, voltage value of DC component: -900 V, between AC peaks). The charging roller and the photoconductor drum were pre-driven at a voltage value of 1600 V). Then, after raising the temperature of the charging roller to 25 ° C. by pre-driving, the voltage between AC peaks was adjusted. Then, by applying the frequency of the AC component: 3KHz, the voltage value of the DC component: -900V, and the voltage value of the adjusted AC peak voltage, the image area ratio: 5% horizontal band chart / A4 horizontal printing is performed. It started. Then, if the temperature of the charging roller is lower than the predetermined temperature after printing 5000 sheets, the charging roller and the photoconductor drum are pre-driven to raise the charging roller to a predetermined temperature, and then the AC peak voltage is adjusted. This was performed again, and the adjusted AC peak voltage was applied to print 5000 sheets further. The same process was repeated every time 5000 sheets were printed, and a total of 30,000 sheets were printed. The predetermined temperature in each treatment was determined according to Table 1 above.

As a main component of the image forming apparatus, the photoconductor drum uses an organic photoconductor drum in which a photosensitive layer (thickness 25 μm) made of polycarbonate resin is formed on the outer peripheral surface of an aluminum substrate at 400 mm / sec. Rotated. The charging roller was made of a conductive rubber having an outer diameter of φ12 mm (epichlorohydrin rubber containing an ionic conductive agent) and provided with a protective layer containing nylon resin as a main component. The developing apparatus was provided with a developing sleeve that was rotationally driven at a linear speed of 600 mm / min, and was subjected to reverse development with a two-component developer. The two-component developer is produced by an emulsion polymerization method, has a volume average particle size of 6.5 μm, is composed of toner particles externally treated with fine particles of silica or titania, and contains a toner having negative charge. Using. Further, a voltage having the same polarity as the charging polarity of the photoconductor drum was applied to the developing sleeve. The lubricant supply device used a conductive fur brush (conductive polyester fiber) having a shaft diameter of 14 mm and a brush bristles length of 3 mm, and was rotated in the same direction as the rotation direction of the photoconductor drum. In addition, zinc stearate was used as the solid lubricant, and the solid lubricant was pressed and held against the brush by a compression spring. The photoconductor cleaner is made of urethane rubber and has a rebound resilience of 50% (25 ° C.), JIS standard A hardness of 70 °, thickness of 2 mm, free length of 10 mm, and width of 324 mm. The load was set to 20 N / mm and the contact angle was set to 15 °. As the intermediate transfer belt, an endless belt made of a polyimide resin imparted with conductivity was used.

(Example 2)
Using the same image forming apparatus as in Example 1, a total of 30,000 sheets were printed in units of 5,000 sheets in the same manner as in Example 1. In Example 2, when the temperature of the charging roller is less than a predetermined temperature, the frequency of the AC component of the superimposed voltage is temporarily increased from 3 KHz to 6 KHz to raise the temperature of the charged roller, and then the AC peak of the superimposed voltage. The AC voltage was adjusted.

(Example 3)
Using the same image forming apparatus as in Example 1, a total of 30,000 sheets were printed in units of 5,000 sheets in the same manner as in Example 1. In Example 3, when the temperature of the charging roller is less than a predetermined temperature, the voltage value of the DC component of the superimposed voltage is temporarily increased from −900V to -1200V to raise the temperature of the charging roller, and then the superimposed voltage. The voltage between AC peaks was adjusted.

(Example 4)
Using the same image forming apparatus as in Example 1, a total of 30,000 sheets were printed in units of 5,000 sheets in the same manner as in Example 1. In Example 4, when the temperature of the charging roller is less than a predetermined temperature, the AC peak voltage of the superimposed voltage is temporarily increased from 1600V to 2000V to raise the temperature of the charging roller, and then the AC peak of the superimposed voltage. The AC voltage was adjusted.

(Comparative example)
Using the same image forming apparatus as in Example 1, every 5,000 sheets were printed, the AC peak voltage was adjusted without pre-driving, and a total of 30,000 sheets were printed.

(Evaluation of photoconductor depletion)
After printing of 30,000 sheets of each of Examples 1 to 4 and Comparative Example, the surface thickness of each photoconductor drum was measured to evaluate the amount of wear of the photoconductor drum. If the amount of wear is equal to or less than the amount of wear of the photoconductor at the time of printing 30,000 sheets, which is derived from the target value of the life of the photoconductor drum, it is evaluated as “◯”, and if it is not less than or equal to that, it is evaluated as “x”. Table 2 shows the driving conditions, the initial preliminary driving time, and the evaluation results of Examples 1 to 5 and Comparative Examples.

With reference to Table 2, it can be seen that in the comparative example, the deterioration of the photoconductor drum is promoted after printing 30,000 sheets, whereas in Examples 1 to 4, the deterioration of the photoconductor drum is suppressed. Further, when the charging roller is heated by pre-driving, if any one of the frequency of the AC component, the voltage value of the DC component, and the voltage value of the AC peak voltage is increased, the charging roller can be activated in a short time. It can be seen that the temperature rises.

Therefore, it was confirmed that the deterioration of the photoconductor drum was suppressed by adjusting the AC peak voltage after heating the charging roller by the preliminary drive. It was also confirmed that if any one of the frequency of the AC component, the voltage value of the DC component, and the voltage value of the AC peak voltage is increased during the preliminary drive of the charging roller, the temperature rise time can be shortened. rice field.

1 Image forming device,
10 Control unit,
20 Memory
30 Operation panel,
40 Image forming part,
41 Transfer belt,
42Y, 42M, 42C, 42K image drawing unit,
43Y, 43M, 43C, 43K primary transfer roller,
44 Secondary transfer roller,
50 Fixing part,
60 Paper feed section,
100 paper,
421 Photoreceptor drum,
422 Charging device,
422a Charging roller,
422b power supply,
423 exposure equipment,
424 developer,
425 Lubricant supply device,
426 Photoreceptor cleaner,
427 Eraser,
451 DC power supply,
452 AC power supply,
453 current sensor,
454 Surface electrometer.

Claims (10)

A charging member that comes into contact with or rotates close to the image carrier and discharges to the image carrier to charge the surface of the image carrier.
A power supply that applies a superposed voltage that superimposes a DC voltage and an AC voltage to the charging member, and
A surface electrometer that measures the surface potential of the image carrier, and
An in-flight temperature sensor that detects the in-flight temperature inside the device,
It has a control unit that adjusts the peak-to-peak voltage of the AC voltage, and has.
The control unit adjusts the peak voltage after raising the temperature of the charging member to a predetermined temperature or higher, and sets the adjusted adjustment value as the output at the time of image formation.
The predetermined temperature is a temperature higher than the in-flight temperature determined according to the in-flight temperature detected by the in-flight temperature sensor.
The adjustment of the peak voltage by the control unit is performed by detecting the surface potential of the image carrier with the surface electrometer.
Image forming device. A charging member that comes into contact with or rotates close to the image carrier and discharges to the image carrier to charge the surface of the image carrier.
A power supply that applies a superposed voltage that superimposes a DC voltage and an AC voltage to the charging member, and
An in-flight temperature sensor that detects the in-flight temperature inside the device,
It has a control unit that adjusts the peak-to-peak voltage of the AC voltage, and has.
The control unit adjusts the peak voltage after raising the temperature of the charging member to a predetermined temperature or higher, and sets the adjusted adjustment value as the output at the time of image formation.
The predetermined temperature is a temperature higher than the in-flight temperature determined according to the in-flight temperature detected by the in-flight temperature sensor.
The adjustment of the peak voltage by the control unit is performed by detecting the current value of the current flowing from the power supply to the charging member.
Image forming device. The control unit adjusts the peak voltage when the number of prints of the print job is equal to or more than a predetermined number, and executes the print job by using the adjusted adjusted value. 2. The image forming apparatus according to 2. The control unit raises the temperature of the charging member by performing a preliminary drive, which is an operation of rotating the charging member and the image carrier while applying the superimposed voltage to the charging member by the power source. Item 3. The image forming apparatus according to any one of Items 1 to 3. The image forming apparatus according to claim 4 , wherein when the pre-driving is performed, the control unit increases the frequency of the AC voltage as compared with the case of normal image forming. The image forming apparatus according to claim 4 or 5 , wherein when performing the pre-driving, the control unit increases the DC voltage as compared with the case of normal image forming. The image forming apparatus according to any one of claims 4 to 6 , wherein when performing the pre-driving, the control unit increases the inter-peak voltage of the AC voltage as compared with the case of normal image forming. The image forming apparatus according to any one of claims 4 to 7 , wherein the control unit determines whether or not to perform the preliminary drive based on the temperature of the charging member. The image forming apparatus according to any one of claims 4 to 8 , wherein the control unit continues the preliminary drive until the temperature of the charging member reaches the predetermined temperature. The image forming apparatus according to claim 8 or 9 , wherein the control unit detects the temperature of the charged member by detecting the current value of the current flowing from the power source to the charged member.

Images