JP2020134762A - Image forming device - Google Patents

Abstract

To provide an image forming device having a charging member being in contact with an image carrier, and capable of detecting a potential on the image carrier with high detection accuracy.SOLUTION: A control unit acquires a first value as the least common multiple of the circumferential length of at least one of a first charging roller and a second charging roller and the circumferential length of a photosensitive drum, and a second value as the length of a sheet and a prescribed interval in the direction of conveyance. The control unit divides the first value by the second value when the first value is larger than the second value, and divides the second value by the first value when the second value is larger than the first value. The control unit sets a division value made integer by one of round-off, round-down and round-up of decimal numbers of a numerical value obtained by diving the first value by the second value or a numerical value obtained by dividing the second value by the first value, as a cycle on which the charged potential on the surface of the photosensitive drum is detected by potential detection means when forming an image.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image forming apparatus such as a copier or a printer using an electrophotographic method.

Conventionally, in an electrophotographic image forming apparatus, the surface of an image carrier such as a photosensitive drum is uniformly charged by a charging means, and then colored toner is developed and visible on an electrostatic latent image created by exposure. Form an image (toner image). A configuration is known in which the image carrier is charged by a plurality of charging means in order to stabilize the potential on the surface of the image carrier (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-163600

In recent years, in an image forming apparatus, in order to grasp the potential on the image carrier as a numerical value, a potential detecting means is provided, and the latent image state can be grasped in real time by detecting the potential of the dark part on the image carrier. It has been demanded. When detecting the dark part potential on the image carrier, it is preferable to detect the dark part potential at regular intervals. However, in the image forming apparatus, when the dark part potential on the image carrier is detected at a preset cycle, the bright part potential may be detected by the potential detecting means depending on the size of the recording material forming the image. Therefore, it was difficult to detect the dark potential at regular intervals. Further, in the image forming apparatus, when the charged member comes into contact with the image carrier, there is a problem that the detection accuracy of the dark potential state is lowered unless the periodicity of contact between the charged member and the image carrier is taken into consideration. ..

Therefore, an object of the present invention is to provide an image forming apparatus having a charging member in contact with an image carrier and capable of detecting a potential on the image carrier with high detection accuracy.

The image forming apparatus according to the present invention is a first transport means for transporting a plurality of sheets at predetermined intervals, a rotatable photoconductor, and a first one that rotates in contact with the photoconductor to charge the surface of the photoconductor. And the second charging roller, which rotates in contact with the photoconductor on the downstream side in the rotation direction of the photoconductor from the first charging roller to charge the surface of the photoconductor. An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the photoconductor and an electrostatic latent image formed on the surface of the photoconductor are developed as a toner image by applying a developing voltage. A developing means, a potential detecting means for detecting the charging potential on the surface of the photoconductor, a transfer means for transferring a toner image on the surface of the photoconductor to a sheet conveyed by the conveying means, and the first charging roller. The first value as the minimum common multiple of the peripheral length of at least one of the second charging roller and the peripheral length of the photoconductor, and the second value as the length of the sheet and the predetermined interval in the transport direction. When the first value is larger than the second value, the first value is divided by the second value, and when the second value is larger than the first value, the second value is divided. Divide by the first value, divide the first value by the second value, or divide the second value by the first value, and then round off, round down, or round up to an integer. It is characterized by including a setting means for setting a value as a cycle for detecting the charging potential by the potential detecting means at the time of forming an image.

Further, the image forming apparatus according to the present invention includes a transport means for transporting a roll sheet in which a continuous sheet is wound around a central portion, a rotatable photoconductor, and the photoconductor that rotates in contact with the photoconductor. A second charging roller that charges the surface of the photoconductor and a second charging roller that contacts and rotates with the photoconductor on the downstream side of the photoconductor in the rotation direction of the first charging roller to charge the surface of the photoconductor. Charging roller, electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoconductor, and electrostatic latent image formed on the surface of the photoconductor by applying a developing voltage. A developing means for developing an image as a toner image, a potential detecting means for detecting the charging potential on the surface of the photoconductor, and a transfer means for transferring the toner image on the surface of the photoconductor to a roll sheet conveyed by the conveying means. A cutting portion that cuts the roll sheet to which the toner image is transferred by the transfer means into an output sheet, at least one peripheral length of the first charging roller and the second charging roller, and the photoconductor. When the first value is larger than the second value in the first value as the minimum common multiple of the peripheral length of the above and the second value as the length in the transport direction of the output sheet, the first value Is divided by the second value, and if the second value is larger than the first value, the second value is divided by the first value, and the first value is divided by the second value or the above. At the time of image formation, the period for forming an image on the output sheet is the number of divided values obtained by rounding, rounding down, or rounding up the value obtained by dividing the second value by the first value. It is characterized by including a setting means for setting a cycle for detecting the charging potential by the potential detecting means.

In addition, the image forming apparatus according to the present invention is a first charging roller that charges the surface of the photoconductor by contacting and rotating the transport means for transporting the recording material, the rotatable photoconductor, and the photoconductor. A second charging roller that comes into contact with the photoconductor and rotates to charge the surface of the photoconductor on the downstream side of the photoconductor in the rotation direction from the first charging roller, and the charged photosensitizer. An electrostatic latent image forming means for forming an electrostatic latent image on the surface of a body, and a developing means for developing an electrostatic latent image formed on the surface of the photoconductor as a toner image by applying a developing voltage. , The potential detecting means for detecting the charging potential on the surface of the photoconductor, the transfer means for transferring the toner image on the surface of the photoconductor to the recording material conveyed by the conveying means, the first charging roller and the above. As the minimum common multiple of at least one circumferential length with the second charging roller, the circumferential length of the photoconductor, and the length in the rotational direction of the photoconductor from the writing start position to the writing end position of the electrostatic latent image. When the first value is larger than the second value in the first value of the above and the second value as the peripheral speed of the photoconductor, the first value is divided by the second value, and the first value is divided by the second value. When the second value is larger than the first value, the second value is divided by the first value, and the first value is divided by the second value or the second value is divided by the first value. It is characterized by including a setting means for setting the divided value as a cycle for detecting the charging potential by the potential detecting means at the time of forming an image.

According to the present invention, it has a charging member that comes into contact with the image carrier, and can detect the potential on the image carrier with high detection accuracy.

The schematic block diagram which shows the image forming apparatus which concerns on 1st Embodiment. The schematic block diagram of the image forming part which concerns on 1st Embodiment. The schematic block diagram of the charging apparatus which concerns on 1st Embodiment. The operation sequence diagram of the image forming apparatus which concerns on 1st Embodiment. The control block diagram of the image forming apparatus which concerns on 1st Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 1st Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 2nd Embodiment. The schematic block diagram of the image forming apparatus which concerns on 3rd Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 3rd Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 4th Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 5th Embodiment. The flowchart which shows the potential detection cycle control of the image forming apparatus which concerns on 6th Embodiment.

<First Embodiment>
Hereinafter, the image forming apparatus according to the first embodiment will be described with reference to the drawings.

[Image forming device]
FIG. 1 is a configuration diagram of an image forming apparatus 1 according to the first embodiment. As shown in FIG. 1, the image forming apparatus 1 is a full-color electrophotographic image forming apparatus having four photosensitive drums and using an intermediate transfer method. The image forming apparatus 1 includes four image forming units (process units) PY, PM, PC, and PK corresponding to each toner color of yellow, magenta, cyan, and black as image forming means for forming a toner image. There is. Each image forming unit PY, PM, PC, PK is detachably arranged on the main body of the apparatus, and has photosensitive drums 11Y, 11M, 11C, and 11K which are drum-type and rotatable photoconductors as an image carrier. are doing. Further, each image forming unit PY, PM, PC, PK has a charging device 12Y, 12M, 12C, 12K for charging the photosensitive drums 11Y, 11M, 11C, 11K. The charging devices 12Y, 12M, 12C, 12K have a first charging roller 121Y, 121M, 121C, 121K and a second charging roller 122Y, 122M, 122C, 122K, which will be described in more detail later. To do.

Each image forming unit PY, PM, PC, PK is a charged photosensitive drum 11Y, 11M. It has exposure devices 13Y, 13M, 13C, 13K as an electrostatic latent image forming means for forming an electrostatic latent image by outputting a laser beam corresponding to image information on the surfaces of 11C, 11K. Further, each image forming unit PY, PM, PC, PK is subjected to a developing voltage, so that the photosensitive drums 11Y, 11M. It has developing devices 14Y, 14M, 14C, 14K as a developing means for developing an electrostatic latent image formed on the surface of 11C, 11K as a toner image.

Below each image forming unit PY, PM, PC, PK, an intermediate transfer belt 31 which is an endless belt body that can orbitally move as an intermediate transfer body is arranged. The intermediate transfer belt 31 is stretched on the drive roller 33, the tension roller 34, and the secondary transfer inner roller 32. The drive roller 33 transmits the driving force from a drive motor (not shown) to rotate the intermediate transfer belt 31 in the direction of the arrow in FIG. 1 (clockwise).

The intermediate transfer belt 31 is composed of a belt having an elastic layer with a soft surface in order to cope with a diversified recording material, prevents transfer omission of the recording material having an uneven surface, and coats paper or OHP. Prevents transfer defects called "hollow" that are likely to occur on paper. The intermediate transfer belt 31 has a three-layer structure consisting of a base material, an elastic layer, and a coat layer, and has a total thickness of about 360 μm. The base material has a thickness of 80 to 90 μm and is made of a conductive polyimide resin material. The elastic layer is formed by laminating 200 to 300 μm of chloroprene rubber on a base material, and has a JIS-A hardness of 60 degrees. The coat layer is laminated to ensure the releasability of the supported toner particles and the recording material, and is the outermost layer having a thickness of 5 to 15 μm in which the fluororesin is dispersed in the binder of the preurethane resin.

The intermediate transfer belt 31 is urged toward the photosensitive drums 11Y, 11M, 11C, 11K by the primary transfer rollers 35Y, 35M, 35C, 35K which are arranged inside and come into contact with the inner peripheral surface of the intermediate transfer belt 31. .. As a result, in the image forming apparatus 1, the outer peripheral surface of the intermediate transfer belt 31 comes into contact with the photosensitive drums 11Y, 11M, 11C, 11K, and the primary transfer is performed between the photosensitive drums 11Y, 11M, 11C, 11K and the intermediate transfer belt 31. A portion (primary transfer nip portion) is formed.

The electrical resistivity of the intermediate transfer belt 31 is adjusted so that the volume resistivity is 1 × 109 to 1 × 1011 Ω · cm and the surface resistivity is 1 × 1011 to 1 × 1013 Ω. Further, the primary transfer rollers 35Y, 35M, 35C, and 35K are driven to rotate with the rotation of the intermediate transfer belt 31, and the primary transfer bias voltage (for example,) from the primary transfer bias power supply (not shown) is opposite to the charging polarity of the toner. + 1500V) is applied.

It is preferable to use the primary transfer rollers 35Y, 35M, 35C, 35K having a resistance value of 1 × 102 to 1 × 108 Ω when + 2 kV is applied in a measurement environment at a temperature of 23 ° C. and a humidity of 50%. In the first embodiment, the primary transfer rollers 35Y, 35M, 35C, 35K are derived from an ion conductive sponge roller having an outer diameter of 16 mm and a core metal diameter of 8 mm formed by mixing a nitrile rubber and an ethylene-epicrolhydrin copolymer. It is configured.

In the image forming apparatus 1 of the first embodiment, the toner has a negative charging polarity and the primary transfer bias voltage is positive. Therefore, a bias electric field is formed in the primary transfer unit to move the charged toner particles toward the primary transfer rollers 35Y, 35M, 35C, 35K. Then, in the image forming apparatus 1, the toner images supported on the photosensitive drums 11Y, 11M, 11C, and 11K are sequentially electrostatically transferred (primary transfer) to the surface of the intermediate transfer belt 31 as another image carrier. A toner image in which four color toners are superimposed is formed.

Each image forming unit PY, PM, PC, PK is a static elimination device 16Y, 16C that eliminates the residual potential remaining on the photosensitive drums 11Y, 11M, 11C, 11K after passing through the primary transfer rollers 35Y, 35C, 35M, 35K. , 16M, 16K. Further, each image forming unit PY, PM, PC, PK is a cleaning member 17Y that removes the toner image remaining on the photosensitive drums 11Y, 11M, 11C, 11K after passing through the primary transfer rollers 35Y, 35C, 35M, 35K. , 17K, 17C, 17K.

Each image forming unit PY, PM, PC, PK has potential detecting means 18Y, 18M, 18C, 18K for detecting the charging potential on the surface of the photosensitive drums 11Y, 11M, 11C, 11K. The potential detecting means 18Y, 18M, 18C, 18K are downstream of the exposure apparatus 13Y, 13M, 13C, 13K and in the rotation direction (counterclockwise) of the photosensitive drums 11Y, 11M, 11C, 11K, and the developing apparatus 14Y, 14M, It is arranged at an upstream position of 14C and 14K.

In the first embodiment, the sheet P1 as a recording material is stored in a form of being loaded in the recording material hangars 61 to 64, and is conveyed at the timing of forming an image by the conveying means 61a to 64a (image forming timing). Will be done. The sheets P1 sent out by the conveying means 61a to 64a pass through the conveying path 3 and the like, and are conveyed to the resist roller pair 76. When continuously forming images, the transport means 61a to 64a transport the plurality of sheets P1 at predetermined intervals.

The resist roller pair 76 abuts the sheet P1 to imitate the tip and correct the skew. Further, the resist roller pair 76 conveys the sheet P1 to the secondary transfer device 4 having the secondary transfer inner roller 32 and the secondary transfer outer roller 41 at a predetermined timing in synchronization with the image formation timing on the sheet P1. ..

In the toner image transferred to the intermediate transfer belt 31, the secondary transfer inner roller 32 and the secondary transfer outer roller 41 face each other as the intermediate transfer belt 31 rotates, and the intermediate transfer belt 31 and the secondary transfer outer roller 41 face each other. It is conveyed to the secondary transfer portion N (secondary transfer nip) formed between the roller 41 and the roller 41. A positive secondary transfer bias voltage, which is opposite to the charging polarity of the toner, is applied to the secondary transfer outer roller 41 from a secondary transfer bias power supply (not shown).

In the image forming apparatus 1, a recording in which negative electrode toner is transferred from the intermediate transfer belt 31 between the secondary transfer inner roller 32 and the secondary transfer outer roller 41 to the secondary transfer unit N by a transfer roller or the like. An electric field is formed in the direction of moving toward the sheet P1 as a material. As a result, the toner image on the intermediate transfer belt 31 (on the intermediate transfer body) is transferred (secondary transfer) onto the sheet P1. The sheet P1 to which the toner image is transferred in the secondary transfer unit is conveyed to the fixing device 5 as a fixing means for melting and fixing the toner image by heating and pressurizing, and the toner image is fixed to the sheet P1.

In the case of single-sided printing, the image forming apparatus 1 ejects the sheet P1 on which the toner image is fixed to the output tray 66 outside the apparatus main body by the ejection roller 78. In the case of double-sided printing, the image forming apparatus 1 reverses the sheet P1 with the reversing roller 79, and then reverts the sheet P1 inverted by the conveying roller 8 provided in the reversing conveying path to the image forming units PY, PM, PC, PK. It is transported and a series of processes related to the above-mentioned image formation are executed. After executing a series of processes, the image forming apparatus 1 ejects the sheet P1 to the output tray 66 outside the apparatus main body by the ejection roller 78.

In this way, the image forming apparatus 1 sequentially transfers and superimposes the toner images of each color formed by the image forming portions PY, PM, PC, and PK on the intermediate transfer belt 31. Then, after the primary transfer, the image forming apparatus 1 collectively transfers the secondary transfer to the sheet P1 such as paper, and fixes the secondary transferred four-color toner image to form a four-color full-color image. The primary transfer rollers 35Y, 35M, 35C, 35K, the intermediate transfer belt 31, and the secondary transfer device 4 transfer the toner image on the surface of the photosensitive drums 11Y, 11M, 11C, 11K in the first embodiment to the sheet P1. Consists of a transfer means to be used.

[Image forming part]
Next, the configuration of the image forming unit PY, PM, PC, and PK will be described by taking the black image forming unit PK as an example. The yellow, magenta, and cyan image forming units PY, PM, and PC are configured in the same manner as the black image forming unit PK except for the difference in toner color. Therefore, the elements having the same configuration and action as the image forming unit PK have the same numbers as the reference numerals (for example, the cartridge 10Y of the image forming unit PY, PM, PC similar to the cartridge 10K of the image forming unit PK). , 10M, 10C) will be added and the description will be omitted. In the present embodiment, four image forming portions PY, PM, PC, and PK are arranged in the order of yellow, magenta, cyan, and black along the rotation direction of the intermediate transfer belt 31, but the arrangement is changed. The number and combination of colors is not limited to this.

FIG. 2 is a schematic view of the image forming unit PK in the first embodiment. As shown in FIG. 2, the image forming unit PK has a first charging roller 121K and a second charging roller 122K as a charging device 12K that comes into contact with the photosensitive drum 11K. The first charging roller 121K is driven to rotate when it comes into contact with the photosensitive drum 11K. Further, the first charging roller 121K is in contact with the charging portion cleaning roller 123K that cleans the surface of the first charging roller 121K. The second charging roller 122K is arranged on the downstream side of the photosensitive drum 11K in the rotation direction with respect to the first charging roller 121K, and is driven to rotate when it comes into contact with the photosensitive drum 11K. Further, the second charging roller 122K is in contact with the charging portion cleaning roller 124K that cleans the surface of the first charging roller 121K.

In the first embodiment, the image forming unit PK is configured as a cartridge 10K in which a photosensitive drum 11K, a charging device 12K, a static elimination device 16K, a cleaning member 17K, and a potential detecting means 18K are integrated, and is a development device 14K. It has a separate structure. The image forming unit PK may have an integrated configuration including a developing device 14K. Further, the image forming unit PK is arranged in the main body of the image forming apparatus 1 if the potential on the photosensitive drum 11K can be detected with respect to the potential detecting means 18K, and has a configuration separate from the image forming unit PK. You may.

[Photosensitive drum]
The image forming unit PK has a photosensitive drum 11K as a rotating drum type electrophotographic photosensitive member. In the first embodiment, the photosensitive drum 11K has a diameter of 84 mm and a length of 370 mm in the longitudinal direction, and is rotationally driven counterclockwise at a process speed (peripheral speed) of about 350 mm / sec about the center. ..

The photosensitive drum 11K has a layer structure of an organic photoconductor including a photosensitive layer formed of an OPC (organic optical semiconductor) having negative charging characteristics. Specifically, the photosensitive drum 11K has a surface protection layer, a charge transport layer, a charge generation layer, an injection blocking layer, an undercoat layer, and a cylinder in this order from the outside in the radial direction. The surface protective layer is provided to improve the cleanability. The charge transport layer is provided for transporting charges. The charge generation layer is provided to generate charges by light irradiation. The injection blocking layer is provided to suppress the passage of holes generated in the charge generation layer and allow only electrons to pass through. The undercoat layer is provided so as to suppress the interference of light depending on the structure of the cylinder and not to interfere with the transport of the electric charge generated in the upper layer. The cylinder is a conductive substrate and is made of aluminum in the first embodiment.

[Charging device]
FIG. 3 is a schematic view showing the charging device 12K according to the first embodiment. As shown in FIG. 3, in the first charging roller 121K, both ends of the core metal 121a (support member) in the longitudinal direction (rotational axis direction) are rotatably held by the bearing 125, and as an urging means. Is urged toward the photosensitive drum 11K by the pressing spring 127 of. As a result, the first charging roller 121K is pressed against the surface of the photosensitive drum 11K with a predetermined pressing force, and rotates clockwise in accordance with the rotation of the photosensitive drum 11K. Further, in the second charging roller 122K, both ends of the core metal 122a in the longitudinal direction are rotatably held by the bearing 126 and urged toward the photosensitive drum 11K by the pressing spring 128. As a result, the second charging roller 122K is pressed against the surface of the photosensitive drum 11K with a predetermined pressing force in substantially the same manner as the first charging roller 121K, and rotates clockwise in accordance with the rotation of the photosensitive drum 11K. ..

In the first embodiment, the first charging roller 121K has a length of 330 mm and a diameter of 14 mm in the longitudinal direction. Further, the first charging roller 121K has a three-layer structure in which a lower layer 121b, an intermediate layer 121c, and a surface layer 121d are sequentially laminated on the outer periphery of the core metal 121a.

The core metal 121a is a stainless steel round bar having a diameter of 6 mm. The lower layer 121b is an electron conductive layer formed of foamed EPDM (ethylene propylene diene rubber) in which carbon is dispersed, has a specific gravity of 0.5 g / cm ^ 3, a volume resistivity of 107 to 109 Ω · cm, and a thickness of about. It is 3.5 mm. The intermediate layer 121c is formed of NBR (nitrile rubber) in which carbon is dispersed, has a volume resistivity of 102 to 105 Ω · cm, and has a thickness of about 500 μm. The surface layer 121d is an ionic conductive layer formed by dispersing tin oxide and carbon in an alcohol-available nylon resin of a fluorine compound, has a volume resistivity of 107 to 10 Ω · cm, and has a surface roughness (JIS standard 10-point average surface roughness). Rz) is 1.5 μm and the thickness is about 5 μm.

In the first embodiment, the second charging roller 122K is configured to have the same diameter as the first charging roller 121K. Further, the second charging roller 122K has a core metal 122a, a lower layer 121b, an intermediate layer 121c and a core metal 122a, a lower layer 122b, an intermediate layer 122c and a surface layer 122d which are substantially the same as those of the first charging roller 121K. It has a layered structure.

The first charging roller 121K is electrically connected to a high-voltage power supply HV1 as a first voltage applying member for applying a charging bias. The high-voltage power supply HV1 has a DC voltage generating unit (DC power supply), and applies a DC voltage to the first charging roller 121K. The second charging roller 122K is electrically connected to the high voltage power supply HV2 as the second voltage applying member for applying the charging bias. The high-voltage power supply HV2 has a DC voltage generating unit (DC power supply) and an AC voltage generating unit (AC power supply), and applies a bias in which an AC voltage is superimposed on the DC voltage to the second charging roller 122K. The image forming unit PK applies a charging bias to the first charging roller 121K and the second charging roller 122K to charge the surface of the rotating photosensitive drum 11K with a predetermined negative electrode potential.

In the image forming unit PK, the first charging roller 121K and the second charging roller 121K so that the charging potential on the photosensitive drum 11K is about −800V at the developing position where the toner image is formed from the electrostatic latent image by the developing device 14K. A charging bias is applied to the charging roller 122K. Specifically, a DC voltage of -1700 V is applied to the first charging roller 121K, and a DC voltage of −850 V, an AC voltage of 1500 Vpp, and a frequency of 2.9 kHz are applied to the second charged roller 122K. ..

The image forming unit PK is a direct current applied when the first charging roller 121K and the second charging roller 122K are configured to charge a predetermined potential in a state where they are close to each other without contacting the photosensitive drum 11K. The voltage and AC voltage are not limited to the above examples.

[Exposure device]
The exposure apparatus 13K in the first embodiment is a laser beam scanning exposure apparatus using a semiconductor laser light source and a polygon mirror engineering system. In the image forming apparatus 1, the laser fragrance control circuit determines the exposure output of the exposure apparatus 13K so that a desired image density level can be obtained with respect to the laser output signal. The exposure apparatus 13K writes the electrostatic latent image of the image on the charged photosensitive drum 11K by the binary area gradation using PWM (pulse width modulation). As a result, the image forming unit PK performs image forming having density gradation.

[Developer]
The developing device 14K supplies a developer (toner) to the electrostatic latent image on the photosensitive drum 11K, and makes the electrostatic latent image manifest as a toner image. In the first embodiment, the developing device 14K is composed of a two-component magnetic brush developing type reversing developing device.

The developing device 14K includes a developing container that houses a two-component developer and a developing sleeve that selectively adheres toner to the electrostatic latent image on the photosensitive drum 11K. The two-component developer contained in the developing container is formed as a mixture of toner and magnetic carriers, and the toner concentration (TD ratio) of the toner and carriers mixed at a weight ratio of about 9:91 is 9%. It is a two-component developer.

The toner has an average particle size of about 6 μm obtained by pulverizing and classifying a resin binder mainly composed of polyester mixed with a pigment. As the carrier, metals such as surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium, rare earths and alloys thereof, or magnetic particles such as oxide ferrite can be used, and the method for producing the magnetic particles is particularly limited. Not done. The carrier has a volume average particle size of 20 to 50 μm, preferably 30 to 40 μm, and a resistivity of 107 Ωcm or more, preferably 108 Ωcm or more. In the first embodiment, a core mainly composed of ferrite is coated with a silicon resin, and a carrier having an average particle size of 35 μm, a resistivity of 5 × 108 Ωcm, and a magnetization amount of 200 emu / cc is used.

The developing sleeve is arranged in a state where the distance from the photosensitive drum 11K is maintained at about 250 μm at the position closest to the photosensitive drum 11K, and faces the photosensitive drum 11K to form a developing unit. The developing sleeve is rotationally driven in the forward direction of the rotational direction of the photosensitive drum 11K. The developing sleeve has a magnet roller inside, and the magnetic force of the magnet roller causes the two-component developer to be rotationally conveyed to the developing unit as the developing sleeve rotates. The magnetic brush layer formed on the surface of the developing sleeve is formed into a predetermined thin layer by a developer coating blade (not shown).

A predetermined development bias is applied to the development sleeve from a high-voltage power source (not shown). The development bias applied to the development sleeve is a vibration voltage obtained by superimposing a DC voltage and an AC voltage. Specifically, when the charging potential on the photosensitive drum 11K is −800 V, a development bias having a DC voltage of −640 V, an AC voltage of 1300 Vpp, and a frequency of 10 kHz is applied to the developing sleeve.

The developing device 14K selectively adheres the toner in the two-component developer corresponding to the electrostatic latent image on the photosensitive drum 11K by the electric field of the development bias, and develops the electrostatic latent image as a toner image. At this time, the charge amount of the toner developed on the photosensitive drum 11K is about 30 μC / g. The developer on the developing sleeve that has passed through the developing section is returned to the developing agent reservoir in the developing container as the developing sleeve rotates.

[Static elimination device]
The static elimination device 16K has a mechanism for statically eliminating the residual potential on the photosensitive drum 11K that has passed through the primary transfer roller 35K (see FIG. 1) by light energy. The static eliminator 16K of the first embodiment has a red LED having a dominant wavelength λD = 650 nm as an electro-optical characteristic as a light emitting element, and executes constant current control that can be changed by a high-voltage power supply.

[Cleaning member]
The cleaning member 17K is arranged to clean the residual toner image remaining on the surface of the photosensitive drum 11K without being transferred to the intermediate transfer belt 31. The image forming unit PK of the first embodiment has a cleaning blade as a cleaning member 17K. The image forming unit PK may have a fur brush or the like as the cleaning member 17K.

[Potential detecting means]
The potential detecting means 18K faces the photosensitive drum 11K, detects the charging potential on the surface of the photosensitive drum 11K, and is arranged at a position downstream of the exposure device 13K and upstream of the developing device 14K in the rotation direction of the photosensitive drum 11K. It is installed. The potential detecting means 18K detects the charging potential on the surface of the photosensitive drum 11K between the papers when the sheets P1 are continuously passed through the sheets at predetermined intervals (between the papers). The details of the cycle for detecting the charging potential will be described later.

[Operation sequence]
FIG. 4 is an operation sequence diagram at the time of image formation.

(1) Initial rotation operation (pre-multi-rotation process)
The pre-multi-rotation process is a start operation period (start operation period, warming period) at the time of starting the printer. The image forming apparatus 1 rotates and drives the photoconductor drum by turning on the start switch, and executes a predetermined process equipment preparatory operation such as starting the fixing apparatus to a predetermined temperature.

(2) Printing preparation rotation operation (pre-rotation process)
The pre-rotation process is a preparatory rotation operation period before image formation from the print signal-on to the actual image formation (printing) process operation, and when a print signal is input during the initial rotation operation, the initial rotation It is executed following the operation. When there is no input of the print signal, the image forming apparatus 1 temporarily stops the drive of the main motor after the end of the initial rotation operation, stops the rotation drive of the photosensitive drum, and keeps the image forming apparatus 1 in the standby state until the print signal is input. .. When the print signal is input, the image forming apparatus 1 executes the print preparation rotation operation.

(3) Printing process, transfer process (image forming process, image forming process)
In the printing step and the transfer step, the print preparation rotation operation is completed, and then the image forming process on the photosensitive drum is executed, the toner image formed on the photosensitive drum surface is transferred to the sheet P1, and the toner image is fixed by the fixing device. This is the period during which the image formation is printed out. In the image forming apparatus 1, in the continuous printing (continuous printing) mode, the above printing process is repeatedly executed for n sheets of a predetermined set number of prints.

In the first embodiment, the image forming apparatus 1 acquires the relationship between job information, particularly information on the sheet P1, and continuously conveyed sheets P1 (between papers) at the time of printing in the printing process, and obtains a potential. Reflect in the calculation process of detection cycle control. The details of the calculation process of the potential detection cycle control will be described later. This printing process constitutes the time of image formation in the first embodiment.

(4) Inter-paper process In the inter-paper process, in the continuous printing mode, after the rear end of the sheet P1 passes through the secondary transfer section N, until the tip of the next sheet P1 reaches the secondary transfer section N. This is the non-passing state period of the sheet P1 at the secondary transfer unit N during the period. This inter-paper process constitutes the non-image forming time in the first embodiment.

(5) Back-rotation operation The back-rotation operation is a period in which the main motor is continuously driven for a while even after the printing process of the last sheet P1 is completed to continuously drive the photoconductor drum to execute a predetermined back-rotation operation. Is.

(6) When the predetermined post-rotation operation is completed, the standby image forming apparatus 1 stops driving the main motor, stops rotating the photosensitive drum, and is in the standby state until the next print start signal is input. keep. In the case of printing only one sheet, the image forming apparatus 1 goes into a standby state through a back rotation operation after the printing is completed. When the print start signal is input in the standby state, the image forming apparatus 1 shifts to the forward rotation process.

[Control unit]
FIG. 5 is a control block diagram of the image forming apparatus 1 of the first embodiment. In the image forming apparatus 1, the control unit 500 receives a print operation command from the operation unit 503 that accepts the user's operation shown in FIG. 5 or an external output device (not shown). The image formation control unit 501 controls the image formation process by the image formation units PY, PM, PC, and PK and the sheet transfer operation by the sheet transfer unit. The CPU 501a executes the image forming operation according to the program stored in the ROM 501b. Further, the CPU 501a stores the rewritable data temporarily or permanently necessary for the image forming operation in the RAM 501c. In the first embodiment, the ROM 501b contains data on the length between papers in the transport direction, data on the perimeters of the photosensitive drum, the first and second charging rollers, and data on the first and second charging rollers. Data on the circumference and the least common multiple of the circumference of the photosensitive drum are stored.

The image processing control unit 502 generates and processes image data. The CPU 502a sequentially reads programs from the ROM 502b that stores the image processing control procedure (image processing control program), and executes the image processing operation according to the program. Further, the RAM 502c is used as a storage area for work for storing input data. In the first embodiment, the ROM 502b stores data regarding the length of the sheet P1 in the transport direction.

[Potential detection cycle control]
The control unit 500 executes potential detection cycle control in which the potential detection means 18Y, 18M, 18C, 18K calculates and sets the cycle for detecting the charging potential on the surface of the photosensitive drums 11Y, 11M, 11C, 11K. Hereinafter, the potential detection cycle control in which the potential detecting means 18K detects the charging potential on the surface of the photosensitive drum 11K in the black image forming unit PK will be described as an example. The potential detection cycle control in the yellow, magenta, and cyan image forming units PY, PM, and PC is also executed in the same manner except for the difference in toner color from the black image forming unit PK.

As described above, in the first embodiment, since the first charging roller 121K and the second charging roller 122K are both configured to have the same diameter of φ14 mm, their peripheral lengths are also configured to be the same. .. The control unit 500 includes the least common multiple of the peripheral length of the first charging roller 121K and the peripheral length of the photosensitive drum 11K, the length of the sheet P1 in the transport direction, and the length of the sheet P1 that is continuously transported in the transport direction. And the period detected by the potential detecting means 18K are set. Since the circumferences of the first and second charging rollers 121K and 122K are equal, the control unit 500 calculates the least common multiple of the circumferences of the second charging rollers 122K and the photosensitive drum 11K. It may be configured. Further, the control unit 500 may be configured to obtain the least common multiple of the peripheral lengths of both the first and second charging rollers 121K and 122K and the peripheral lengths of the photosensitive drum 11K.

Below, the diameters of the first and second charging rollers 121K and 122K are φ14 mm, the diameter of the photosensitive drum 11K is φ84 mm, and the length of the A3R size sheet P1 that continuously passes paper in the transport direction (inter-paper length). The potential detection cycle control will be described by taking the case where is 28 mm as an example. FIG. 6 is a flowchart showing the potential detection cycle control executed by the control unit 500 in the first embodiment.

First, the control unit 500 detects the start of the image formation job by inputting a print signal from the operation unit 503 or an external output device (not shown) (S101). Here, the image formation job is a period from the start of image formation to the completion of image formation based on the print signal (image formation signal) that forms an image on the recording material. That is, the image forming job is a period during which a series of operations are performed from the input of the print signal shown in FIG. 5 to the end of the backward rotation operation. The control unit 500 starts the potential detection cycle control by detecting the start of the image forming job.

Next, the CPU 502a of the image processing control unit 502 of the control unit 500 acquires data regarding the length (transport length) of the sheet P1 in the transport direction from the input print signal from the ROM 502b (S102). Next, the CPU 501a of the image formation control unit 501 of the control unit 500 acquires the inter-paper length of the sheet P1 continuously conveyed from the input print signal from the ROM 501b (S103). By executing the processes of steps S102 and S103, the control unit 500 acquires the data of the transport length and the inter-paper length from the ROMs 501b and 502b and holds them in the RAM 501c.

Next, the CPU 501a acquires data (perimeter data) regarding the perimeters of the photosensitive drum 11K, the first charging roller 121K, and the second charging roller 122K from the ROM 501b (S104). Next, the CPU 501a calculates the least common multiple X1 of the first charging roller 121K and the photosensitive drum 11K (S105). In the processes of steps S104 and S105, the CPU 501a has the same circumference as the first charging roller 121K because the circumference of the first charging roller 121K and the circumference of the second charging roller 122K are the same length. The least common multiple X1 with the circumference of the photosensitive drum 11K is calculated. The CPU 501a calculates the least common multiple X1 of the peripheral length of the first charging roller 121K and the peripheral length of the photosensitive drum 11K, so that the second charging roller 122K has the same peripheral length as the peripheral length of the first charging roller 121K. And the least common multiple of the circumference of the photosensitive drum 11K can also be calculated.

Table 1 shows data of the least common multiple with respect to the peripheral length of the charging roller and the peripheral length of the photosensitive drum stored in the ROM 501a. The least common multiple values shown in Table 1 are the least common multiples of the value obtained by rounding off the decimal point of the peripheral length of the charging roller and converting it into an integer and the value obtained by rounding off the decimal point of the photosensitive drum and converting it into an integer. It is a value calculated in advance.

第１の帯電ローラ１２１Ｋの直径がφ１４ｍｍであり、感光ドラム１１Ｋの直径がφ８４である場合、最小公倍数Ｘ１は、表１より２６４である。この、最小公倍数Ｘ１が、第１の実施形態における第１値を構成する。

When the diameter of the first charging roller 121K is φ14 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple X1 is 264 from Table 1. The least common multiple X1 constitutes the first value in the first embodiment.

Next, the CPU 501a adds the transport length and the inter-paper length to calculate the added value A1 (S106). In this process, the CPU 501a adds the data of the transport length and the inter-paper length acquired in steps S102 and S103. Since the sheet P1 of the first embodiment has an A3R size, the transport length is 420 mm. Since the paper-to-paper length is 28 mm, the added value A1 is 448 mm. The added value A1 constitutes the second value in the first embodiment.

Next, the CPU 501a executes the division calculation process using the least common multiple X1 and the addition value A1 (S107). In the division calculation process, the CPU 501a first compares the least common multiple X1 and the addition value A1, determines which value is the larger value, and determines the division and the dividend in the division. As described above, the least common multiple X1 is 264 mm, and the added value A1 is 448 mm. Therefore, the CPU 501a determines that the addition value A1 is a value larger than the least common multiple X1, and determines that the addition value A1 is a division and the least common multiple X1 is a divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to calculate an integer divided value. In the first embodiment, the division value "2" is obtained by rounding off the decimal point of the value "1.69 ..." calculated by dividing the addition value A1 by the least common multiple X1 and converting it into an integer. Is calculated.

Next, the CPU 501a determines the calculated division value as the cycle (potential detection cycle) in which the potential detection means 18K detects the potential (S108), and ends the potential detection cycle control. In the process of step S108, since the CPU 501a calculated the division value "2" in the process of step S107, the potential detection cycle is determined to be the cycle in which the two sheets P1 pass through the secondary transfer unit N.

By executing the potential detection cycle control by the CPU 501a, the image forming apparatus 1 sets a potential detection cycle for detecting the charging potential on the surface of the photosensitive drum 11K by the potential detecting means 18K, and periodically sets the potential detection cycle on the surface of the photosensitive drum 11K. The charging potential of is detected. The control unit 500 having the CPU 501a and setting the potential detection cycle constitutes the setting means in the first embodiment.

As described above, in the image forming apparatus 1 of the first embodiment, the minimum common multiple X1 of the peripheral lengths of the first charging roller 121K and the photosensitive drum 11K and the total length between the sheet P1 and the paper in the transport direction are used. From the added value A1, the period for which the potential detecting means 18K detects the charging potential is set. As a result, the image forming apparatus 1 detects the charging potential on the surface of the photosensitive drum 11K in a potential detection cycle including the periodicity of the portion where the first charging roller 121K and the photosensitive drum 11K come into contact with each other, which is high. It can be detected with detection accuracy.

<Second embodiment>
Next, the image forming apparatus 1 according to the second embodiment will be described. In the image forming apparatus 1 of the second embodiment, the diameter of the first charging roller 121K and the diameter of the second charging roller 122K are different diameters. In this respect, the image forming apparatus 1 of the second embodiment is different from the first embodiment described above. Since the other configurations are the same as those of the first embodiment, the components common to the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

Below, the diameter of the first charging roller 121K is φ24 mm, the diameter of the second charging roller 122K is φ14 mm, the diameter of the photosensitive drum 11K is φ84 mm, and the length of the A3R size sheet P1 for continuous paper transfer in the transport direction. A case where the diameter (paper-to-paper length) is 28 mm will be described as an example. FIG. 7 is a flowchart showing the potential detection cycle control executed by the control unit 500 in the second embodiment.

First, the control unit 500 detects the start of the image forming job by inputting a print signal from the operation unit 503 or an external output device (not shown), substantially similar to the process of step S101 shown in FIG. 6 (S201). ). Next, in the control unit 500, the CPU 502a of the image processing control unit 502 receives data on the length (transport length) of the sheet P1 in the transport direction from the input print signal, substantially similar to the process of step S102 shown in FIG. Is obtained from ROM 502b (S202). Next, the CPU 501a of the image formation control unit 501 of the control unit 500 sets the inter-paper length of the sheet P1 continuously conveyed from the input print signal to the ROM 501b, substantially the same as the process of step S103 shown in FIG. Obtained from (S203).

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the first charging roller 121K from the ROM 501b (S204). Next, the CPU 501a calculates the least common multiple Y1 of the first charging roller 121K and the photosensitive drum 11K (S205). In the processing of steps S204 and S205, the CPU 501a calculates the least common multiple Y1 from the peripheral length data of the first charging roller 121K and the photosensitive drum 11K. When the diameter of the first charging roller 121K is φ24 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple Y1 is 6600 mm from Table 1. The least common multiple Y1 constitutes the first value in the second embodiment.

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the second charging roller 122K from the ROM 501b (S206). Next, the CPU 501a calculates the least common multiple Z1 of the second charging roller 122K and the photosensitive drum 11K (S207). In the processing of steps S206 and S207, the CPU 501a calculates the least common multiple Z1 from the peripheral length data of the second charging roller 122K and the photosensitive drum 11K. When the diameter of the second charging roller 122K is φ14 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple Z1 is 264 mm from Table 1. The least common multiple Z1 constitutes the first value in the second embodiment.

Next, the CPU 501a calculates the added value A1 by adding the transport length and the inter-paper length in substantially the same manner as in the process of step S106 shown in FIG. 6 (S208). Since the sheet P1 of the second embodiment has an A3R size, the transport length is 420 mm. Since the paper-to-paper length is 28 mm, the added value A1 is 448 mm. The added value A1 constitutes the second value in the second embodiment.

Next, the CPU 501a executes the division calculation process using the least common multiple Y1, the least common multiple Z1, and the addition value A1 (S209). In the division calculation process, the CPU 501a first compares the least common multiple Y1 and the addition value A1, determines which value is the larger value, and determines the division and the dividend in the division. As described above, the least common multiple Y1 is 6600 mm, and the added value A1 is 448 mm. Therefore, the CPU 501a determines that the least common multiple Y1 is a value larger than the addition value A1, and determines that the least common multiple Y1 is the divisor and the addition value A1 is the divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to convert it into an integer. In the second embodiment, the value "15" is calculated by rounding off the decimal point of the value "14.73 ..." calculated by dividing the least common multiple Y1 by the addition value A1 and converting it into an integer. To do.

Next, the CPU 501a compares the least common multiple Z1 with the added value A1, determines which value is the larger value, and determines the divisor and the dividend in the division. As described above, the least common multiple Z1 is 264 mm, and the added value A1 is 448 mm. Therefore, the CPU 501a determines that the addition value A1 is a value larger than the least common multiple Z1, and determines that the addition value A1 is a division and the least common multiple Z1 is a divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to convert it into an integer. In the second embodiment, the value "2" is calculated by rounding off the decimal point of the value "1.69 ..." calculated by dividing the addition value A1 by the least common multiple Z1 and converting it into an integer. To do.

Next, the CPU 501a determines whether or not the value calculated by the division calculation process using the least common multiple Y1 is smaller than the value calculated by the division calculation process using the least common multiple Z1 (S210). .. In this process, the CPU 501a compares the value calculated by using the least common multiple Y1 in the process of step S209 with the value calculated by using the least common multiple Z1, and determines which value is to be the division value. Judging.

In the process of step S210, when it is determined that the value calculated by the division calculation process using the least common multiple Y1 is smaller (Yes), the CPU 501a sets the value calculated using the least common multiple Y1 as the division value. .. Then, the CPU 501a determines the division value calculated by using the least common multiple Y1 as the potential detection cycle of the potential detection means 18K (S211), and ends the potential detection cycle control.

On the other hand, in the process of step S210, when it is determined that the value calculated by the division calculation process using the least common multiple Y1 is larger (No), the CPU 501a uses the value calculated using the least common multiple Z1 as the division value. Set. Then, the CPU 501a determines the division value calculated using the least common multiple Z1 as the potential detection cycle of the potential detection means 18K (S212), and ends the potential detection cycle control.

In the second embodiment, as described above, the value calculated by the division calculation process using the least common multiple Y1 is the value "15", and the value calculated by the division calculation process using the least common multiple Z1 is the value. It is "2". Therefore, the CPU 501a proceeds from step S210 to step S212, sets the value "2" as the division value, and determines the potential detection cycle as the cycle in which the two sheets P1 pass through the secondary transfer unit N. ..

By executing the potential detection cycle control by the CPU 501a, the image forming apparatus 1 can obtain an appropriate potential detection cycle even when the circumferences of the first charging roller 121K and the second charging roller 122K are different. Set.

As described above, the image forming apparatus 1 of the second embodiment has an appropriate potential by controlling the potential detection cycle even when the peripheral lengths of the first charging roller 121K and the second charging roller 122K are different. The detection cycle can be set. As a result, the image forming apparatus 1 has a potential detection cycle including the periodicity of the portion where the first charging roller 121K, the second charging roller 122K, and the photosensitive drum 11K come into contact with each other on the surface of the photosensitive drum 11K. Since the charging potential is detected, it can be detected with high detection accuracy.

<Third embodiment>
Next, the image forming apparatus 1a according to the third embodiment will be described. The image forming apparatus 1a of the third embodiment has a configuration in which an image is formed on a continuous sheet (roll sheet) wound in a roll shape as a recording material. In this respect, the image forming apparatus 1a of the third embodiment is different from the first and second embodiments described above. Since the other configurations are the same as those of the first embodiment, the components common to the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

[Image forming device]
FIG. 8 is a block diagram of the image forming apparatus 1a according to the third embodiment. As shown in FIG. 8, in the image forming apparatus 1a, the roll sheet is supplied from the roll sheet supply apparatus 101 as a conveying means to the apparatus main body. In the roll sheet supply device 101, a roll sheet P2 in which a sheet is wound around a roll core portion P2a as a central portion is arranged. In the roll sheet supply device 101, the roll sheet P2 is supplied to the main body of the image forming device 1a by rotating the roll core portion P2a.

In the image forming apparatus 1a, the roll sheet P2 has the transfer belts 36Y, 36M, at the timing when the tip of the toner image on the surface of the photosensitive drums 11Y, 11M, 11C, 11K coincides with the position where the transfer is started on the roll sheet P2. It is transported to 36C and 36K. The transfer belts 36Y, 36M, 36C, 36K constitute a transfer means for transferring the toner image on the surface of the photosensitive drums 11Y, 11M, 11C, 11K in the third embodiment to the roll sheet P2.

The roll sheet P2 on which the toner image is transferred on the upper surface is conveyed to the fixing device 5, and the toner image is melt-fixed by heating and pressurizing. The roll sheet P2 on which the toner image is fixed is conveyed by the size of the sheet (output sheet) output from the cutting section 102, then cut by the cutting section 102, cut into the output sheet P2b, and loaded on the loading section 103. Toner.

[Potential detection cycle control]
In the third embodiment, the first charging roller 121K and the second charging roller 122K are both configured to have the same diameter of φ24 mm, and the peripheral length is also configured to be the same. The control unit 500 has a minimum common multiple of the peripheral length of the first charging roller 121K and the peripheral length of the photosensitive drum 11K, and the length of the roll sheet P2 where the image is formed (image forming region) and the margin in the conveying direction. The total and the period detected by the potential detecting means 18K are set. Since the circumferences of the first and second charging rollers 121K and 122K are equal, the control unit 500 calculates the least common multiple of the circumferences of the second charging rollers 122K and the photosensitive drum 11K. It may be configured. Further, the control unit 500 may be configured to obtain the least common multiple of the peripheral lengths of both the first and second charging rollers 121K and 122K and the peripheral lengths of the photosensitive drum 11K. Further, since the total length of the image forming region and the margin in the transport direction is the same as the length of the output sheet P2b in the transport direction, the total length of the image forming region and the margin in the transport direction is replaced with the total length of the output sheet P2b. The potential detection cycle may be set by using the length in the transport direction of. In addition, the margin constitutes a non-image forming region in which an image is not formed.

Below, the diameters of the first and second charging rollers 121K and 122K are φ24 mm, the diameter of the photosensitive drum 11K is φ84 mm, the length of the image forming region in the transport direction is 482.6 mm, and the length of the margin in the transport direction is 33 mm. The potential detection cycle control will be described by taking the case of. FIG. 9 is a flowchart showing the potential detection cycle control executed by the control unit 500 in the third embodiment.

First, the control unit 500 detects the start of the image formation job by inputting a print signal from the operation unit 503 or an external output device (not shown) (S301). Next, the CPU 502a of the image processing control unit 502 of the control unit 500 acquires data regarding the length (convey length) of the image forming region of the roll sheet P2 in the transport direction from the input print signal from the ROM 502b (S302). ). Next, the CPU 501a of the image formation control unit 501 of the control unit 500 acquires the length (margin length) of the margin of the roll sheet P2 in the transport direction from the ROM 501b from the input print signal (S303). By executing the processes of steps S302 and S303, the control unit 500 acquires the data of the transport length and the margin length from the ROMs 501b and 502b and holds the data in the RAM 501c.

Next, the CPU 501a acquires the peripheral length data of each of the photosensitive drum 11K, the first charging roller 121K, and the second charging roller 122K from the ROM 501b (S304). Next, the CPU 501a calculates the least common multiple X1 of the first charging roller 121K and the photosensitive drum 11K (S305). In the processing of steps S304 and S305, the CPU 501a has the same circumference as the first charging roller 121K because the circumference of the first charging roller 121K and the circumference of the second charging roller 122K are the same length. The least common multiple X1 with the circumference of the photosensitive drum 11K is calculated. The CPU 501a calculates the least common multiple X1 of the peripheral length of the first charging roller 121K and the peripheral length of the photosensitive drum 11K, so that the second charging roller 122K has the same peripheral length as the peripheral length of the first charging roller 121K. And the least common multiple of the circumference of the photosensitive drum 11K can also be calculated.

When the diameter of the first charging roller 121K is φ24 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple X1 is 6600 mm from Table 1 described above. The least common multiple X1 constitutes the first value in the third embodiment.

Next, the CPU 501a adds the transport length and the margin length to calculate the added value A2 (S306). In this process, the CPU 501a adds the data of the transport length and the margin length acquired in steps S302 and S303. The roll sheet P2 of the third embodiment has an image forming region having a transport length of 482.6 mm and a margin length of 33 mm. Therefore, the added value A2 is 515.6 mm. The added value A2 constitutes the second value in the third embodiment.

Next, the CPU 501a executes the division calculation process using the least common multiple X1 and the addition value A2 (S307). In the division calculation process, the CPU 501a first compares the least common multiple X1 and the addition value A2, determines which value is the larger value, and determines the division and the dividend in the division. As described above, the least common multiple X1 is 6600 mm, and the added value A2 is 515.6 mm. Therefore, the CPU 501a determines that the least common multiple X1 is a value larger than the addition value A2, and determines that the least common multiple X1 is the divisor and the addition value A2 is the divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to calculate an integer divided value. In the third embodiment, the division value "13" is obtained by rounding off the decimal point of the value "12.80 ..." calculated by dividing the least common multiple X1 by the addition value A2 and converting it into an integer. Is calculated.

Next, the CPU 501a determines the calculated division value as the cycle (potential detection cycle) in which the potential detection means 18K detects the potential (S308), and ends the potential detection cycle control. In the process of step S308, since the CPU 501a calculated the division value "13" in the process of step S307, the potential detection cycle is determined to be a cycle of forming 13 images on the roll sheet P2.

As described above, the image forming apparatus 1a of the third embodiment has the least common multiple X1 of the peripheral lengths of the first charging roller 121K and the photosensitive drum 11K, and the transport length and the margin length of the image forming region of the roll sheet P2. The potential detection cycle is set from the total addition value A2. As a result, even when the recording material is the roll sheet P2, the image forming apparatus 1a has a potential detection cycle including the periodicity of the portion where the first charging roller 121K and the photosensitive drum 11K come into contact with each other. The charging potential on the surface of 11K can be detected and detected with high detection accuracy.

<Fourth Embodiment>
Next, the image forming apparatus 1a according to the fourth embodiment will be described. In the image forming apparatus 1a of the fourth embodiment, the diameter of the first charging roller 121K and the diameter of the second charging roller 122K are different. In this respect, the image forming apparatus 1a of the fourth embodiment is different from the third embodiment described above. Since the other configurations are the same as those in the third embodiment, the components common to the third embodiment are designated by the same reference numerals and the description thereof will be omitted.

Below, the diameter of the first charging roller 121K is φ24 mm, the diameter of the second charging roller 122K is φ14 mm, the diameter of the photosensitive drum 11K is φ84 mm, the transport length of the image forming region is 482.6 mm, and the margin length is 33 mm. The potential detection cycle control will be described by taking a case as an example. FIG. 10 is a flowchart showing the potential detection cycle control executed by the control unit 500 in the fourth embodiment.

First, the control unit 500 detects the start of the image forming job by inputting a print signal from the operation unit 503 or an external output device (not shown), substantially similar to the process of step S301 shown in FIG. 9 (S401). ). Next, the CPU 502a of the image processing control unit 502 of the control unit 500 obtains data regarding the transport length of the image forming region of the roll sheet P2 from the input print signal in substantially the same manner as the processing of step S302 shown in FIG. Obtained from ROM 502b (S402). Next, the CPU 501a of the image formation control unit 501 of the control unit 500 acquires the margin length of the roll sheet P2 from the ROM 501b from the input print signal in substantially the same manner as the process of step S303 shown in FIG. 9 (S403). ..

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the first charging roller 121K from the ROM 501b (S404). Next, the CPU 501a calculates the least common multiple Y1 of the first charging roller 121K and the photosensitive drum 11K (S405). In the processing of steps S404 and S405, the CPU 501a calculates the least common multiple Y1 from the peripheral length data of the first charging roller 121K and the photosensitive drum 11K. When the diameter of the first charging roller 121K is φ24 mm and the diameter of the photosensitive drum 11K is φ84 mm, the least common multiple Y1 is 6600 mm from Table 1. The least common multiple Y1 constitutes the first value in the fourth embodiment.

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the second charging roller 122K from the ROM 501b (S406). Next, the CPU 501a calculates the least common multiple Z1 of the second charging roller 122K and the photosensitive drum 11K (S407). In the processing of steps S406 and S407, the CPU 501a calculates the least common multiple Z1 from the peripheral length data of the second charging roller 122K and the photosensitive drum 11K. When the diameter of the second charging roller 122K is φ14 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple Z1 is 264 mm from Table 1. The least common multiple Z1 constitutes the first value in the fourth embodiment.

Next, the CPU 501a calculates the added value A2 by adding the transport length and the margin length in substantially the same manner as in the process of step S306 shown in FIG. 9 (S408). The roll sheet P2 of the fourth embodiment has an image forming region having a transport length of 482.6 mm and a margin length of 33 mm. Therefore, the added value A2 is 515.6 mm. The added value A2 constitutes the second value in the fourth embodiment.

Next, the CPU 501a executes the division calculation process using the least common multiple Y1, the least common multiple Z1, and the addition value A2 (S409). In the division calculation process, the CPU 501a first compares the least common multiple Y1 and the addition value A2, determines which value is the larger value, and determines the division and the dividend in the division. As described above, the least common multiple Y1 is 6600 mm, and the added value A2 is 515.6 mm. Therefore, the CPU 501a determines that the least common multiple Y1 is a value larger than the addition value A2, and determines that the least common multiple Y1 is the divisor and the addition value A2 is the divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to convert it into an integer. In the fourth embodiment, the value "13" is calculated by rounding off the decimal point of the value "12.80 ..." calculated by dividing the least common multiple Y1 by the addition value A2 and converting it into an integer. To do.

Next, the CPU 501a compares the least common multiple Z1 with the added value A2, determines which value is the larger value, and determines the divisor and the dividend in the division. As described above, the least common multiple Z1 is 264 mm, and the added value A2 is 515.6 mm. Therefore, the CPU 501a determines that the addition value A2 is a value larger than the least common multiple Z1, determines that the addition value A2 is a division and the least common multiple Z1 is a divisor.

Next, the CPU 501a divides the divisor by a divisor and rounds off the obtained numerical value after the decimal point to convert it into an integer. In the fourth embodiment, the value "2" is calculated by rounding off the decimal point of the value "1.95 ..." calculated by dividing the addition value A1 by the least common multiple Z1 and converting it into an integer. To do.

Next, the CPU 501a determines whether or not the value calculated by the division calculation process using the least common multiple Y1 is smaller than the value calculated by the division calculation process using the least common multiple Z1 (S410). .. In this process, the CPU 501a compares the value calculated by using the least common multiple Y1 in the process of step S409 with the value calculated by using the least common multiple Z1, and determines which value is to be the division value. Judging.

In the process of step S410, when it is determined that the value calculated by the division calculation process using the least common multiple Y1 is smaller (Yes), the CPU 501a sets the value calculated using the least common multiple Y1 as the division value. .. Then, the CPU 501a determines the division value calculated by using the least common multiple Y1 in the potential detection cycle of the potential detection means 18K (S411), and ends the potential detection cycle control.

On the other hand, in the process of step S410, when it is determined that the value calculated by the division calculation process using the least common multiple Y1 is larger (No), the CPU 501a uses the value calculated using the least common multiple Z1 as the division value. Set. Then, the CPU 501a determines the division value calculated using the least common multiple Z1 as the potential detection cycle of the potential detection means 18K (S412), and ends the potential detection cycle control.

In the fourth embodiment, as described above, the value calculated by the division calculation process using the least common multiple Y1 is the value "13", and the value calculated by the division calculation process using the least common multiple Z1 is the value. It is "2". Therefore, the CPU 501a proceeds from step S410 to step S412, sets the value "2" as the division value, and determines the potential detection cycle as the cycle for forming two images on the roll sheet P2.

By executing the potential detection cycle control by the CPU 501a, in the image forming apparatus 1a, even if the peripheral lengths of the first charging roller 121K and the second charging roller 122K are different, an appropriate potential detection cycle can be obtained. Set.

As described above, in the image forming apparatus 1a of the fourth embodiment, the recording material is the roll sheet P2, and the peripheral lengths of the first charging roller 121K and the second charging roller 122K are different. However, an appropriate potential detection cycle can be set by controlling the potential detection cycle. As a result, the image forming apparatus 1a has a potential detection cycle including the periodicity of the portion where the first charging roller 121K, the second charging roller 122K, and the photosensitive drum 11K come into contact with each other on the surface of the photosensitive drum 11K. Since the charging potential is detected, it can be detected with high detection accuracy.

<Fifth Embodiment>
Next, the image forming apparatus 1 according to the fifth embodiment will be described. The image forming apparatus 1 of the fifth embodiment has the length in the rotation direction of the photosensitive drum from the start position to the end position of writing the electrostatic latent image to the photosensitive drum for each formed color at the time of image formation, and the circumference of the photosensitive drum. The speed and the potential detection cycle are set using. In this respect, the image forming apparatus 1 of the fifth embodiment is different from the above-described first to fourth embodiments. Since the other configurations are the same as those of the first embodiment, the components common to the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Further, the potential detection cycle control executed by the image forming apparatus according to the fifth embodiment can be executed regardless of whether the recording material is the sheet P1 or the roll sheet P2.

[Potential detection cycle control]
In the fifth embodiment, the first charging roller 121K and the second charging roller 122K are both configured to have the same diameter of φ14 mm, and the peripheral length is also configured to be the same. The control unit 500 includes the peripheral length of the first charging roller 121K, the peripheral length of the photosensitive drum 11K, and the length in the rotation direction of the photosensitive drum 11K from the start position to the end position of writing the electrostatic latent image on the photosensitive drum 11K. Calculate the least common multiple of (write length). Further, the control unit 500 sets the period detected by the potential detecting means 18K using the calculated least common multiple and the peripheral speed of the photosensitive drum 11K. Since the circumferences of the first and second charging rollers 121K and 122K are the same in the control unit 500, the circumference length of the first charging roller 121K is replaced with the circumference length of the second charging roller 122K when calculating the least common multiple. Perimeter of may be used. Further, the control unit 500 may use the peripheral lengths of both the first and second charging rollers 121K and 122K when calculating the least common multiple.

The following is an example in which the diameters of the first and second charging rollers 121K and 122K are φ14 mm, the diameter of the photosensitive drum 11K is φ84 mm, the peripheral speed is 350 mm / s, and the writing length of the electrostatic latent image is 420 mm. The potential detection cycle control will be described. FIG. 11 is a flowchart showing the potential detection cycle control executed by the control unit 500 when the same image is continuously formed in the fifth embodiment.

First, the control unit 500 detects the start of the image formation job by inputting a print signal from the operation unit 503 or an external output device (not shown) (S501). Next, the CPU 502a of the image processing control unit 502 of the control unit 500 decomposes information regarding each formed color from the input print signal (S502). In this process, the CPU 502a decomposes information for each formed color from the input print signal and acquires information regarding black color.

Next, the CPU 502a calculates the writing length B1 of the electrostatic latent image written on the photosensitive drum 11K (S503). In this process, the CPU 502a sets the writing length B1 of the black electrostatic latent image among the writing lengths of the electrostatic latent images of each formed color at the time of forming one image when continuously forming the same image. calculate. As described above, the writing length B1 of the electrostatic latent image in the fifth embodiment is 420 mm.

Next, the CPU 501a of the image formation control unit 501 of the control unit 500 acquires the perimeter data of each of the photosensitive drum 11K, the first charging roller 121K, and the second charging roller 122K from the ROM 501b (S504). Next, the CPU 501a calculates the least common multiple X1 of the first charging roller 121K and the photosensitive drum 11K (S505). In the processing of steps S504 and S505, since the peripheral length of the first charging roller 121K and the peripheral length of the second charging roller 122K are the same length, the CPU 501a has the same as the peripheral length of the first charging roller 121K. The least common multiple X1 with the circumference of the photosensitive drum 11K is calculated. The CPU 501a calculates the least common multiple X1 of the peripheral length of the first charging roller 121K and the peripheral length of the photosensitive drum 11K, so that the second charging roller 122K has the same peripheral length as the peripheral length of the first charging roller 121K. And the least common multiple of the circumference of the photosensitive drum 11K can also be calculated.

When the diameter of the first charging roller 121K is φ14 mm and the diameter of the photosensitive drum 11K is φ84 mm, the least common multiple X1 is 264 mm from Table 1 described above.

Next, the CPU 501a determines whether or not the writing length B1 of the electrostatic latent image calculated in the process of step S503 is not 0 (S506). In this process, the CPU 501a determines whether or not the electrostatic latent image is written on the photosensitive drum 11K by determining whether or not the writing length B1 of the electrostatic latent image is 0.

If it is determined in the process of step S506 that the write length B1 of the electrostatic latent image is not 0 (Yes), the CPU 501a has the least common multiple X2 of the least common multiple X1 and the write length B1 of the electrostatic latent image. Is calculated (S507). In the fifth embodiment, the CPU 501a calculates 9240 mm as the least common multiple X2 because the least common multiple X1 is 264 mm and the writing length B1 of the electrostatic latent image is 420 mm. The least common multiple X2 constitutes the first value in the fifth embodiment.

On the other hand, when it is determined in the process of step S506 that the writing length B1 of the electrostatic latent image is 0 (No), the CPU 501a determines to apply the least common multiple X1 in the division calculation process (S508). Since the electrostatic latent image is not written on the surface of the photosensitive drum 11K, the CPU 501a uses the least common multiple X1 to determine the potential detection cycle from the periodicity of the first charging roller 121K and the photosensitive drum 11K. Decide to set.

In the fifth embodiment, as described above, since the writing length B1 of the electrostatic latent image is 420 mm and is not 0, the processing proceeds from step S506 to step S507 by the CPU 501a, and the least common multiple X2 is calculated. To.

After executing the process of step S507 or S508, the CPU 501a acquires the peripheral speed A3 of the photosensitive drum 11K (S509). Next, the CPU 501a executes the division calculation process using the least common multiple X1 or the least common multiple X2 and the peripheral speed A3 (S510). In the division calculation process, the CPU 501a first compares the least common multiple X1 or the least common multiple X2 with the peripheral speed A3, determines which value is the larger value, and determines the division and the dividend in the division. ..

As described above, in the fifth embodiment, 9240 mm is calculated as the least common multiple X2. The peripheral speed A3 is 350 mm / s. Therefore, the CPU 501a determines that the least common multiple X2 is a value larger than the peripheral speed A3, determines that the least common multiple X2 is the divisor and the peripheral speed A3 is the divisor.

Next, the CPU 501a calculates the division value by dividing the division by the divisor. In the fifth embodiment, the division value "26.4" is calculated by dividing the least common multiple X2 by the peripheral speed A3.

Next, the CPU 501a determines the calculated division value as the cycle (potential detection cycle) in which the potential detection means 18K detects the potential (S511), and ends the potential detection cycle control. In the process of step S511, since the CPU 501a calculated the division value "26.4" in the process of step S510, the potential detection cycle is determined to be 26.4 seconds.

As described above, the image forming apparatus 1 of the fifth embodiment has the least common multiple X2 of the first charging roller 121K, the peripheral length of the photosensitive drum 11K, and the writing length of the electrostatic latent image of the photosensitive drum 11K, and the photosensitive drum 11K. The potential detection cycle is set from the peripheral speed A3 of the drum 11K. As a result, the image forming apparatus 1 detects the charging potential on the surface of the photosensitive drum 11K in a potential detection cycle including the periodicity of the portion where the first charging roller 121K and the photosensitive drum 11K come into contact with each other, which is high. It can be detected with detection accuracy. Further, the image forming apparatus 1 can periodically detect the charging potential on the surface of the photosensitive drum with high detection accuracy at a different cycle for each forming color of the image according to the writing length of the electrostatic latent image in each color. it can.

<Sixth Embodiment>
Next, the image forming apparatus 1 according to the sixth embodiment will be described. In the image forming apparatus 1a of the sixth embodiment, the diameter of the first charging roller 121K and the diameter of the second charging roller 122K are different. In this respect, the image forming apparatus 1 of the sixth embodiment is different from the fifth embodiment described above. Since the other configurations are the same as those in the fifth embodiment, the components common to the fifth embodiment are designated by the same reference numerals and the description thereof will be omitted.

Below, the diameter of the first charging roller 121K is φ24 mm, the diameter of the second charging roller 122K is φ14 mm, the diameter of the photosensitive drum 11K is φ84 mm, the peripheral speed is 350 mm / s, and the writing length of the electrostatic latent image is 420 mm. The potential detection cycle control will be described by taking the case of. FIG. 12 is a flowchart showing the potential detection cycle control executed by the control unit 500 when the same image is continuously formed in the sixth embodiment.

First, the control unit 500 detects the start of the image forming job by inputting a print signal from the operation unit 503 or an external output device (not shown), substantially similar to the process of step S501 shown in FIG. 11 (S601). ). Next, the CPU 502a of the image processing control unit 502 of the control unit 500 decomposes information regarding each formation color from the input print signal in substantially the same manner as the process of step S502 shown in FIG. 11 (S602). Next, the CPU 502a calculates the writing length B1 of the electrostatic latent image written on the photosensitive drum 11K in substantially the same manner as the processing in step S503 shown in FIG. 11 (S603). As described above, the writing length B1 of the electrostatic latent image in the sixth embodiment is 420 mm.

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the first charging roller 121K from the ROM 501b (S604). Next, the CPU 501a calculates the least common multiple Y1 of the first charging roller 121K and the photosensitive drum 11K (S605). In the processing of steps S604 and S605, the CPU 501a calculates the least common multiple Y1 from the peripheral length data of the first charging roller 121K and the photosensitive drum 11K. When the diameter of the first charging roller 121K is φ24 mm and the diameter of the photosensitive drum 11K is φ84 mm, the least common multiple Y1 is 6600 mm from Table 1.

Next, the CPU 501a acquires the peripheral length data of the photosensitive drum 11K and the second charging roller 122K from the ROM 501b (S606). Next, the CPU 501a calculates the least common multiple Z1 of the second charging roller 122K and the photosensitive drum 11K (S607). In the process of steps S606 and S607, the CPU 501a calculates the least common multiple Z1 from the peripheral length data of the second charging roller 122K and the photosensitive drum 11K. When the diameter of the second charging roller 122K is φ14 mm and the diameter of the photosensitive drum 11K is φ84, the least common multiple Z1 is 264 mm from Table 1.

Next, the CPU 501a determines whether or not the least common multiple Y1 is larger than the least common multiple Z1 (S608). In this process, the CPU 501a sets the values for the write length B1 of the electrostatic latent image to the least common multiple Y1 and the least common multiple Z1 in order to calculate the least common multiple X3 with the write length B1 of the electrostatic latent image in the subsequent processes. Judgment is made to set the smaller value.

When it is determined in the process of step S608 that the least common multiple Y1 is smaller than the least common multiple Z1 (No), the CPU 501a determines to apply the least common multiple Y1 in the subsequent processing (S609). On the other hand, when it is determined in the process of step S608 that the least common multiple Y1 is larger than the least common multiple Z1 (Yes), the CPU 501a decides to apply the least common multiple Z1 in the subsequent processing (S610).

In the sixth embodiment, as described above, since the least common multiple Y1 is larger than the least common multiple Z1, the CPU 501a proceeds from step S608 to step S610, and the application of the least common multiple Z1 is determined.

Next, the CPU 501a determines whether or not the write length B1 of the electrostatic latent image calculated in the process of step S603 is not 0, substantially the same as the process of step S506 shown in FIG. 11 (S611). In this process, when it is determined that the write length B1 of the electrostatic latent image is not 0 (Yes), the CPU 501a has the least common multiple X3 of the least common multiple Y1 or Z1 and the write length B1 of the electrostatic latent image. Is calculated (S612).

In the sixth embodiment, the CPU 501a determines the application of the least common multiple Z1 as described above. Further, in the sixth embodiment, as described above, since the writing length B1 of the electrostatic latent image is 420 mm and is not 0, the processing is advanced from step S611 to step S612 by the CPU 501a, and the least common multiple X3 is set. It is calculated. Since the least common multiple Z1 is 264 mm and the writing length B1 of the electrostatic latent image is 420 mm, the CPU 501a calculates 9240 mm as the least common multiple X3. The least common multiple X3 constitutes the first value in the sixth embodiment.

After executing the process of step S612 or in the process of step S611, when it is determined that the writing length B1 of the electrostatic latent image is 0 (No), the CPU 501a acquires the peripheral speed A3 of the photosensitive drum 11K (No). S613). Next, the CPU 501a executes the division calculation process using the least common multiple Y1, the least common multiple Z1, the least common multiple X3, and the peripheral speed A3 (S614). In the division calculation process, the CPU 501a first compares the least common multiple Y1, the least common multiple Z1 or the least common multiple X3 with the peripheral speed A3, determines which value is the larger value, and determines which value is the larger value. And decide.

As described above, in the sixth embodiment, 9240 mm is calculated as the least common multiple X3. The peripheral speed A3 is 350 mm / s. Therefore, the CPU 501a determines that the least common multiple X3 is a value larger than the peripheral speed A3, determines that the least common multiple X3 is the divisor and the peripheral speed A3 is the divisor.

Next, the CPU 501a calculates the division value by dividing the division by the divisor. In the sixth embodiment, the division value "26.4" is calculated by dividing the least common multiple X3 by the peripheral speed A3.

Next, the CPU 501a determines the calculated division value as the cycle (potential detection cycle) in which the potential detection means 18K detects the potential (S615), and ends the potential detection cycle control. In the process of step S615, since the CPU 501a calculated the division value "26.4" in the process of step S614, the potential detection cycle is determined to be 26.4 seconds.

As described above, in the image forming apparatus 1 of the sixth embodiment, even when the peripheral lengths of the first charging roller 121K and the second charging roller 122K are different, the static electricity in each color is controlled by the potential detection cycle control. The potential detection cycle can be set according to the writing length of the electro-latent image. As a result, the image forming apparatus 1 has a potential detection cycle including the periodicity of the portion where the first charging roller 121K, the second charging roller 122K, and the photosensitive drum 11K come into contact with each other on the surface of the photosensitive drum 11K. Since the charging potential is detected, it can be detected with high detection accuracy. Further, the image forming apparatus 1 can periodically detect the charging potential on the surface of the photosensitive drum with high detection accuracy at a different cycle for each forming color of the image according to the writing length of the electrostatic latent image in each color. it can.

<Other embodiments>
In the first to fourth embodiments, the CPU 501a is configured to calculate an integerized division value by rounding off at the time of executing the division calculation process, but the present invention is not limited to this. The CPU 501a may be configured to be an integer by rounding down or rounding up to the decimal point of the numerical value as a result of division.

Further, in the first to sixth embodiments, the charging device 12K superimposes an AC voltage on the DC voltage on the high voltage power supply HV1 that applies a DC voltage to the first charging roller 121K and the second charging roller 122K. It has, but is not limited to, a high voltage power source HV2 to be applied. The charging device 12K may have a predetermined voltage application member that applies a DC voltage to the first charging roller 121K and superimposes an AC voltage on the DC voltage on the second charging roller 122K.

1,1a ... Image forming apparatus / 4 ... Transfer means (secondary transfer apparatus) / 11Y, 11M, 11C, 11K ... Photoreceptor (photosensitive drum) / 13Y, 13M, 13C, 13K ... Electrostatic latent image forming means (exposure) Equipment) / 14Y, 14M, 14C, 14K ... Developing means (developing device) / 18Y, 18M, 18C, 18K ... Potential detecting means / 31 ... Transfer means (intermediate transfer belt) / 35Y, 35M, 35C, 35K ... Transfer means (Primary transfer roller) / 36Y, 36M, 36C, 36K ... Transfer means (transfer belt) 61a to 64a ... Transfer means / 102 ... Cutting portion / 121Y, 121M, 121C, 121K ... First charging roller / 122Y, 122M, 122C, 122K ... Second charging roller / 500 ... Setting means (control unit) / A1, A2 ... Second value (additional value) / A3 ... Second value (peripheral speed) / HV1 ... First voltage applying member ( High-voltage power supply) / HV2 ... Second voltage application member (high-voltage power supply) / P1 ... Sheet, recording material / P2 ... Roll sheet, recording material / P2b ... Output sheet / X1 to X3, Y1, Z1 ... First value (minimum) common multiple)

Claims (6)

A transport means for transporting a plurality of sheets at predetermined intervals,
With a rotatable photoconductor,
A first charging roller that rotates in contact with the photoconductor and charges the surface of the photoconductor.
A second charging roller that comes into contact with the photoconductor and rotates to charge the surface of the photoconductor on the downstream side in the rotation direction of the photoconductor from the first charging roller.
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoconductor, and
A developing means that develops an electrostatic latent image formed on the surface of the photoconductor as a toner image by applying a developing voltage.
A potential detecting means for detecting the charging potential on the surface of the photoconductor and
A transfer means for transferring a toner image on the surface of the photoconductor to a sheet conveyed by the transfer means, and a transfer means.
The first value as the least common multiple of the peripheral length of at least one of the first charging roller and the second charging roller and the peripheral length of the photoconductor, and the length of the sheet and the predetermined interval in the transport direction. When the first value is larger than the second value, the first value is divided by the second value, and when the second value is larger than the first value, the first value is divided by the second value. , The second value is divided by the first value, and the first value is divided by the second value, or the second value is divided by the first value, and the value after the decimal point is rounded, rounded down, or rounded up. A setting means for setting the division value converted into an integer by the above as a cycle for detecting the charging potential by the potential detecting means at the time of forming an image is provided.
An image forming apparatus characterized in that. A transport means for transporting a roll sheet in which a continuous sheet is wound in the center,
With a rotatable photoconductor,
A first charging roller that rotates in contact with the photoconductor and charges the surface of the photoconductor.
A second charging roller that comes into contact with the photoconductor and rotates to charge the surface of the photoconductor on the downstream side in the rotation direction of the photoconductor from the first charging roller.
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoconductor, and
A developing means that develops an electrostatic latent image formed on the surface of the photoconductor as a toner image by applying a developing voltage.
A potential detecting means for detecting the charging potential on the surface of the photoconductor and
A transfer means for transferring the toner image on the surface of the photoconductor to a roll sheet conveyed by the transfer means, and a transfer means.
A cutting portion that cuts the roll sheet to which the toner image is transferred by the transfer means into an output sheet, and
The first value as the least common multiple of at least one peripheral length of the first charging roller and the second charging roller and the peripheral length of the photoconductor, and the second as the length in the transport direction of the output sheet. In terms of the value, if the first value is larger than the second value, the first value is divided by the second value, and if the second value is larger than the first value, the first value is divided. An integer by dividing two values by the first value, dividing the first value by the second value, or dividing the second value by the first value, rounding off, rounding down, or rounding up. It is provided with a setting means for setting a cycle for forming an image on the output sheet of the number of divided values converted into a cycle for detecting the charging potential by the potential detecting means at the time of forming the image.
An image forming apparatus characterized in that. When the peripheral length of the first charging roller and the peripheral length of the second charging roller are different, the setting means sets the peripheral length of the first charging roller and the least common multiple of the peripheral length of the photoconductor. The value obtained by dividing the value obtained by dividing using the first value as the first value and dividing the value obtained by dividing the value obtained by dividing the value by using the least common multiple of the circumference of the second charging roller and the circumference of the photoconductor as the first value is described. The integerized value and the smaller value are set as the division value.
The image forming apparatus according to claim 1 or 2. Transport means for transporting recording materials and
With a rotatable photoconductor,
A first charging roller that rotates in contact with the photoconductor and charges the surface of the photoconductor.
A second charging roller that comes into contact with the photoconductor and rotates to charge the surface of the photoconductor on the downstream side in the rotation direction of the photoconductor from the first charging roller.
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoconductor, and
A developing means that develops an electrostatic latent image formed on the surface of the photoconductor as a toner image by applying a developing voltage.
A potential detecting means for detecting the charging potential on the surface of the photoconductor and
A transfer means for transferring a toner image on the surface of the photoconductor to a recording material conveyed by the transfer means, and a transfer means.
The circumferential length of at least one of the first charging roller and the second charging roller, the peripheral length of the photoconductor, and the rotation of the photoconductor from the writing start position to the writing end position of the electrostatic latent image. In the first value as the least common multiple of the length in the direction and the second value as the peripheral speed of the photoconductor, when the first value is larger than the second value, the first value is used. Divide by the second value, and if the second value is larger than the first value, divide the second value by the first value and divide the first value by the second value or the second value. A setting means for setting a division value obtained by dividing a value by the first value as a cycle for detecting the charging potential by the potential detecting means at the time of forming an image is provided.
An image forming apparatus characterized in that. When the peripheral length of the first charging roller and the peripheral length of the second charging roller are different, the setting means sets the peripheral length of the first charging roller and the least common multiple of the peripheral length of the photoconductor. ,
The smaller value of the peripheral length of the second charging roller and the least common multiple of the peripheral length of the photoconductor, and the rotation direction of the photoconductor from the writing start position to the writing end position of the electrostatic latent image. And the least common multiple of are used as the first value.
The image forming apparatus according to claim 4. A first voltage applying member that applies a DC voltage to the first charging roller, and
A second voltage application member that superimposes an AC voltage on a DC voltage and applies the AC voltage to the second charging roller is provided.
The image forming apparatus according to any one of claims 1 to 5, wherein the image forming apparatus is characterized in that.

Images