JP2023121586A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can reliably notify an operator that an electrifying roller is not in contact with a photoreceptor drum without providing a special sensor.SOLUTION: An image forming apparatus has: an electrifying roller 12 that can contact and separate from a photoreceptor; a developing unit 15 for forming a toner image on a surface of a photoreceptor drum 11; an image sensor 22 that detects the toner image formed on the surface of the photoreceptor drum 11; and a control part 30. The control part 30 can execute a contact and separation determination mode having a first control section in which the toner image is formed on the photoreceptor drum 11 if the state of contact of the electrifying roller 12 with the photoreceptor drum 11 is abnormal, and the toner image is not formed if the state of contact of the electrifying roller 12 is normal, and a second control section in which the toner image is not formed on the photoreceptor drum 11 regardless of the state of contact of the electrifying roller 12. The control part determines the state of contact of the electrifying roller 12 with the photoreceptor drum 11 based on a result of detection performed by the image sensor 22 in the first control section.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus having a charging roller. More specifically, it relates to an image forming apparatus in which a charging roller can be separated from and in contact with an image carrier.

A roller image forming apparatus that can be attached to and removed from an image carrier is disclosed, for example, in Japanese Patent Application Laid-Open No. 2018-17995 (Patent Document 1). In Patent Document 1, an image forming apparatus includes an image forming section and a control section, and the control section controls the image forming section. The image forming section has an intermediate transfer belt as an image bearing member, a secondary transfer roller, and a toner concentration detection section, and a toner image is formed on the surface of the intermediate transfer belt. The secondary transfer roller can be pressed against and separated from the surface of the intermediate transfer belt. The toner density detection section detects the toner density of the toner image on the intermediate transfer belt after passing through the secondary transfer roller. The controller determines whether the secondary transfer roller is in the pressure contact state or in the separated state based on the detected toner density and the toner density data included in the image data. This provides an image forming apparatus capable of detecting an abnormality of the secondary transfer roller without delaying the operation of the image forming section.

JP 2018-17995 A

A conventional image forming apparatus is configured as described above. In Patent Document 1, the state in which the secondary transfer roller is separated from the intermediate transfer belt, which is the image bearing member, is determined by detecting the toner image that has not been secondary-transferred onto the paper with an image density sensor. That is, in a state in which a toner image is formed in advance on an image carrier, the toner image that has not been secondarily transferred to the paper at the secondary transfer portion is detected by an image density sensor. When a toner image is not formed on the upstream side in the rotation direction of the image carrier from the position corresponding to the charging roller of the image carrier, it was not possible to determine the separation of the roller.

SUMMARY OF THE INVENTION The present invention was made to solve the above-described problems. Another object of the present invention is to provide an image forming apparatus capable of reducing the amount of toner consumed when detecting that the charging roller is separated from the photosensitive drum.

An image forming apparatus according to the present invention includes a photosensitive drum, a charging roller that charges the surface of the photosensitive drum and can be separated from and contacted to the photosensitive drum by a contact/separation mechanism, and a toner image formed on the surface of the photosensitive drum. , an image sensor for detecting the toner image formed on the surface of the photosensitive drum, and a controller. The controller controls a first control section in which a toner image is formed on the photosensitive drum if the contact state of the charging roller with the photosensitive drum is abnormal, and that toner adhesion does not occur if the contact state of the charging roller is normal. and a second control section in which no toner image is formed on the photosensitive drum regardless of the contact state of the charging roller. The contact state of the charging roller to the photosensitive drum is determined based on the detection result of .

That is, in the first control section of the contact/separation determination mode executable by the control unit, if the charging roller is separated from the photosensitive drum (using fogging development), a toner image is formed and the charging roller Since a toner image is not formed if the charging roller is in contact with the photosensitive drum (because fog development is not performed), the contact state of the charging roller with the photosensitive drum can be determined by the image sensor. In the second control section of the contact/separation determination mode that can be executed by the control unit, a toner image is not formed even when the charging roller is separated from the photosensitive drum (because this is a condition in which fog development does not occur). Therefore, the amount of toner image necessary for determining the contact state of the charging roller can be reduced.

Preferably, a charging power supply for applying a predetermined voltage to the charging roller and a developing power supply for applying a predetermined voltage to the developing roller are further provided, and the control section controls the same conditions as those during image formation in the first control section. is applied to the charging roller and the developing roller, and in the second control section, a voltage opposite in polarity to that during image formation is applied to the developing roller, and no voltage is applied to the charging roller. Alternatively, a voltage lower than the discharge start voltage of the charging roller is applied.

More preferably, a transfer member for transferring the toner image on the photosensitive drum to a sheet and a transfer power source for the transfer member are further provided, and the control section controls the transfer member to perform the transfer in a reverse direction different from that during image formation in the first control section. Apply a voltage of polarity.

It is preferable that the control unit controls the time of the first control interval to be shorter than the time of the second control interval.

In one embodiment of the present invention, the image forming apparatus includes a color image forming apparatus for outputting images in a plurality of colors, the color image forming apparatuses each having a photosensitive layer for outputting images in a plurality of colors. It has a set of a plurality of charging rollers and developing rollers including a body drum, and an intermediate transfer member to which the toner image formed on each photosensitive drum is transferred. Based on the detection result of the image sensor arranged to detect the contact state of the plurality of sets of charging rollers and developing rollers with respect to the photosensitive drum is determined.

Even if there are a plurality of pairs of charging rollers and developing rollers, as in a color image forming apparatus, it is determined which pair of charging rollers and developing rollers the detected image belongs to based on the elapsed time from the start of the first control section. becomes possible.

The control unit measures and compares the time from the start of application of a predetermined voltage to the detection of the toner image by the image sensor to a plurality of pairs of charging rollers and developing rollers, thereby determining the contact with the photosensitive drum. A set of charging roller and developing roller that is in an abnormal state may be identified.

The control unit individually sets the time of the first control interval for each of the plurality of pairs of charging rollers and developing rollers, and sets the detection time of the toner image detected by the image sensor and the time of each first control interval. A combination of a charging roller and a developing roller that is in an abnormal contact state with the photoreceptor drum may be identified by the comparison.

The control unit may control, in the first control section, the absolute value of the voltage applied to the plurality of pairs of charging rollers and developing rollers to be smaller than that at the time of image output.

In the first control section, the control unit applies voltages to the developing rollers at different rates compared to the voltage at the time of image output to the plurality of pairs of charging rollers and developing rollers, and the voltages are detected by the image sensor. By comparing the magnitude of the detection value and the voltage applied to the developing roller, the set of the charging roller and the developing roller that is in an abnormal contact state with the photosensitive drum may be specified.

The control unit executes a plurality of first control sections and second control sections for a plurality of sets of charging rollers and developing rollers, thereby controlling the exposure of the plurality of sets of charging rollers and developing rollers. The state of contact with the body drum may be determined.

The photosensitive drum and the charging roller constitute a process unit, and the control unit controls the image sensor to detect the image on the surface of the photosensitive drum in the first control section and the second control section when the process unit is replaced. Alternatively, the contact state of the charging roller with the photosensitive drum may be determined based on the presence or absence of the toner image.

A display unit is further provided, and when the control unit determines that the charging roller is not in contact with the photosensitive drum, the display unit displays a notification requesting confirmation of the contact state of the charging roller with the photosensitive drum. may

Further, when the control unit determines that the charging roller is not in contact with the photosensitive drum, the display unit indicates the charging roller of the process unit that has determined that the charging roller is not in contact with the photosensitive drum. A notification may be displayed so as to confirm the contact state with the photoreceptor drum.

According to the present invention, the contact state of the charging roller with the photosensitive drum can be confirmed in the first control section that can be executed by the control unit of the image forming apparatus using an image sensor that is provided in advance in the image forming apparatus. Further, by providing the second control section that can be executed by the control unit of the image forming apparatus, the toner image is formed on the photoreceptor drum even when the charging roller is not in contact with the photoreceptor drum. can be prevented.

As a result, it is possible to provide an image forming apparatus capable of detecting the contact/separation state of the charging roller with respect to the photosensitive drum and reducing toner consumption.

The above object, other objects, features and advantages of the present invention will become more apparent from the detailed description of embodiments given below with reference to the drawings.

1 is a configuration diagram around a photosensitive drum having a process unit according to an embodiment of the present invention; FIG. It is a figure which shows the control sequence of a 1st control area and a 2nd control area. 5 is a flow chart showing a method for determining a contact state of a charging roller; FIG. 4 is a view showing a contact/separation mechanism that brings the charging roller into contact with the photosensitive drum; 2 is a configuration diagram around a process unit for each color in the color image forming apparatus; FIG. 1 is a diagram showing the overall configuration of a color image forming apparatus; FIG. FIG. 4 is a diagram showing a control sequence in a first method of detecting an abnormality in a color image forming apparatus; 5 is a flow chart showing a method for determining a contact state of a charging roller in a color image forming apparatus; FIG. 10 is a diagram showing a control sequence in a second method of detecting an abnormality in the color image forming apparatus; FIG. 10 is a diagram showing a control sequence in a third method of detecting an abnormality in a color image forming apparatus;

[First embodiment]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration around a contact-type charging roller 12 when the image forming apparatus 10 is a monochrome image forming apparatus 10 according to an embodiment of the present invention. 3 is a diagram showing a state in which developer (toner) 17 is transferred onto paper 38 via unit 18. FIG.

Referring to FIG. 1, an image forming apparatus 10 according to this embodiment includes a grounded photosensitive drum 11 on which a toner image is formed, and a charging roller 12 that applies a predetermined charging bias voltage to the photosensitive drum 11. , an exposure unit 14 arranged downstream of the charging roller 12, a development unit 15 arranged downstream of the exposure unit 14, an image density sensor 22 arranged downstream of the development unit 15, and an image density sensor. 22 so as to be in contact with the photosensitive drum 11, and rotates together with the photosensitive drum 11 to sandwich and convey the paper 38, thereby transferring the toner image on the photosensitive drum 11 to the paper 38. a transfer unit 18, a charge removing unit 19 provided downstream of the transfer unit 18 for removing the potential from the photosensitive drum 11, a waste toner collecting section 20 provided downstream of the charge removing unit 19, and a cleaning blade 21. And prepare.

The charging roller 12 is connected to a negative constant-voltage controlled charging power source 23 and is in contact with the cleaning roller 13 . The developing unit 15 includes a developing roller 16 that supplies toner 17 to the photoreceptor drum 11, and the developing roller 16 is connected to a minus power source 24 for development. A transfer unit (transfer member) 18 is a transfer roller and is connected to a transfer power source 25 .

The image sensor 22 supplies toner from the developing power source 24 to the developing roller 16 in order to always form a stable toner image even if the surrounding environment of the image forming apparatus 10 or the number of image formation sheets increases (usage time increases). It is used when adjusting power supply conditions and the like. Specifically, the image density of the toner image on the photosensitive drum 11 obtained by changing the power supply conditions to the developing roller 16 is detected, and the power supply conditions and the like to be supplied to the developing roller 16 are adjusted so as to optimize the image density. change.

In this embodiment, when the image forming apparatus 10 is installed and when the process unit (the unit including the photoreceptor drum 11 and the charging roller 12) is replaced with a new one, the image sensor 22 provided in advance in the image forming apparatus 10 can: The contact state between the photosensitive drum 11 and the charging roller 12 is determined using so-called fogging development in which a toner image is formed when the charging roller 12 is in a non-contact state.

That is, in this embodiment, if the contact state of the charging roller 12 with the photosensitive drum 11 is abnormal, the control unit 30 forms a toner image on the photosensitive drum 11, and the contact state of the charging roller 12 is A contact/separation determination mode having a first control section in which a toner image is not formed if normal and a second control section in which a toner image is not formed regardless of the contact state of the charging roller 12 can be executed. Based on the detection result (of the toner image) of the image sensor 22 in the control section 1, the contact state (contact/separate state) of the charging roller 12 with respect to the photosensitive drum 11 is determined.

Originally, as described with reference to FIG. 1, if the photosensitive drum 11 and the charging roller 12 are in contact with each other, the voltage (eg, −1200 V) applied by the charging power source 23 during image formation is applied to the charging roller 12 . , the surface of the photosensitive drum 11 is uniformly charged to a predetermined potential (eg, −600 V) via the charging roller 12, and the area exposed according to the printed image by the exposure unit 14 is charged to the potential is lowered to form an electrostatic latent image, and the toner 17 charged to the electrostatic latent image portion from the developing roller 16 is electrically supplied by the developing bias voltage applied by the developing power supply 24, and visualized as a toner image. Therefore, the image sensor 22 detects density information corresponding to the density of the toner image. However, if the exposure unit 14 does not perform exposure, an electrostatic latent image is not formed (there is no or little potential difference between the developing roller 16 to which the developing bias is applied). is not supplied and a toner image is not formed. Therefore, the image density sensor 22 does not detect the toner image. That is, a value corresponding to the surface state of the photosensitive drum 11 itself, that is, the bare surface state (the state in which no toner is present) is detected. On the other hand, if the photosensitive drum 11 and the charging roller 12 are separated from each other, the photosensitive drum 11 is not charged via the charging roller 12 . Therefore, when a developing bias voltage (eg, -400 V) is applied to the developing roller 16, a large potential difference is generated between the developing roller 16 and the photosensitive drum 11, and a large amount of toner 17 is deposited on the photosensitive drum 11 (corresponding to the developing roller 16). A toner image is formed by so-called fogging development in which the toner is electrically transferred to the entire area where the toner image is formed. That is, in the first control section, if the contact state between the charging roller 12 and the photosensitive drum 11 is abnormal, a toner image is formed on the photosensitive drum 11 and detected by the image sensor 22 .

During a normal image forming operation, the transfer unit 18 is connected to a positive power supply to transfer the toner image on the photosensitive drum 11 onto the paper. can be connected to either a positive or a negative power source, and in the first control section, a voltage opposite in polarity to the normal output is applied to the transfer unit 18 . By configuring in this way, it is possible to prevent the transfer unit 18 from being stained with the toner 17 even if there is an abnormality.

On the other hand, in the second control section, the charging roller 12 is applied with, for example, −500 V (when the charging roller 12 reaches 11 is not charged, that is, a voltage lower than the discharge start voltage, which may be 0 V) is applied, and +150 V, for example, is applied to the developing roller.

In order to perform such control and judgment, a control section 30 is provided as shown in FIG. , a developing power supply control unit 24a for controlling the voltage applied to the developing power supply 24, a transfer power supply control unit 25a for controlling the voltage applied to the transfer unit 18, the image sensor 22, and the charging roller 12 are connected to the photosensitive drum 11. It is connected to a display unit 34 or the like that displays that there is no contact. Also, the control unit 30 includes a CPU, a memory, and the like, and controls the entire image forming apparatus 10 .

A specific description will be given below. FIG. 2 is a diagram showing the control sequence of the above-described first control section and second control section in the monochrome image forming apparatus 10 according to one embodiment of the present invention. Referring to FIG. 2, there are, from the top, an on-off signal for the driving motor (not shown) of the photosensitive drum 11, an on-off signal for the output of the charging power source 23 to the charging roller 12, and an on-off signal for the developing power source 24. An on-off signal for the output to the developing roller 16 and an output signal for the image sensor 22 are shown. Here, the first control section is indicated by a, and the second control section is indicated by b.

Referring to FIG. 2, the on-off signal of the drive motor for photosensitive drum 11 is on from the first control section to the second control section. The output to the charging roller 12 is initially 0 V, but is turned ON in the first control section a, the negative voltage (for example, -1200 V) is applied, and the second control section b is entered. Turn off (to -500 V, for example). The output to the developing roller 16 is initially 0V, but is turned ON in the first control section a, a negative voltage (eg, -400V) is applied, and in the second control section b, a positive voltage is applied. A voltage (for example, +150V) is applied, and when the second control section b ends, it is turned off to the original 0V.

That is, in this embodiment, in the first control section a, both the output to the charging roller 12 and the output to the developing roller 16 are turned on, and a predetermined voltage of negative polarity, which is the same condition as during image formation, is applied. If the photosensitive drum 11 and the charging roller 12 are separated from each other, the conditions for fogging development are satisfied, and the fogging phenomenon occurs to form a toner image on the photosensitive drum 11, which is detected by the image sensor. 22 can be detected.

On the other hand, in the second control section b, the output to the charging roller 12 is OFF, or a voltage less than the discharge start voltage is applied, and the output to the developing roller 16 is a voltage with a polarity opposite to that during image formation. is applied and a reverse bias voltage is applied. Therefore, fog development does not occur even if the photosensitive drum 11 and the charging roller 12 are separated from each other. Therefore, the developing roller 16 prevents the toner 17 from electrically moving and adhering to the photosensitive drum 11 .

Note that the output of the image sensor 22 is normally a High signal, but when the charging roller 12 is separated, an image is generated by fog development on the photosensitive drum 11 in the first control section. A Low signal is output as indicated by the middle dotted line.

Here, the first control section (a) is shown to be shorter than the second control section (b). can shorten the length of the toner image formed by That is, it is possible to reduce the amount of toner image required for checking the separation of the charging roller 12 . In particular, when it takes a long time for the toner image formed in the first control section (a) to reach the image sensor 22, by making the second control section (b) longer than the first control section, The amount of toner image formed can be reduced, and the amount of toner consumed can be reduced. In addition, the first control section (a) and the second control section (b) may be equal.

The processing described here will be described with reference to the flowchart shown in FIG. FIG. 3 is a flowchart showing a method of determining the contact state between the photosensitive drum 11 and the charging roller 12 (separation/contact determination mode). Referring to FIG. 3, the CPU of control unit 30 first rotates a driving motor (not shown) to rotate photosensitive drum 11 (step S11, steps will be omitted below). Then, as the first control section, the charging roller 12 is applied with the first charging bias voltage (eg, −1200 V described above), and the developing roller 16 is applied with the first developing bias voltage (eg, −400 V described above). (S12). It is determined whether or not the first time has passed (S13). Here, the first time is a contact/separation confirmation time of the charging roller necessary for forming a band-shaped image on the photosensitive drum 11 by fog development. In S13, if the first time has not elapsed (N in S13), the process returns to S12. As described above, the exposure unit 14 is not operated.

If the first time has elapsed (Y in S13), then in the second control section, the second charging bias voltage (for example, -500 V) is applied to the charging roller 12, and development is performed. A second developing bias voltage (for example, +150 V described above) is applied to the roller 16 (S14). It is determined whether or not the image sensor 22 has detected an image (whether or not a low signal has been detected) (S15).

If the image sensor 22 does not detect an image (signal Low) in S15 (N in S15), the controller 30 controls the second time (the time required for the image density sensor 22 to detect an image (signal Low)). has elapsed (S16), and if not (N in S16), the process returns to S14. If it has passed (Y in S16), the application of the bias voltage to the charging roller 12 and the developing roller 16 is stopped, and the rotation of the drive motor is stopped (S17).

If the image density sensor 22 detects an image (signal Low) in S15 (Y in S15), it is determined that the charging roller 12 is not in contact with the photosensitive drum 11, and the bias to the charging roller 12 and the developing roller 16 is applied. After stopping the application of the voltage and stopping the rotation of the driving motor, the display section 34 displays that the charging roller 12 is not in contact with the photosensitive drum 11 (S18).

As described above, in this embodiment, the control unit 30 controls the developing bias voltage and the charging bias voltage to generate the first control section, which is a section with fog development, in which fog development can occur; A separation/contact determination mode having a second control section in which no fog development occurs is provided so as to be executable.

As a result, the contact/separation state of the charging roller 12 with respect to the photosensitive drum 11 can be detected by the control unit 30 executing the contact/separation determination mode using the existing image sensor 22 without providing an ammeter or a dedicated sensor. can be determined effectively.

In other words, if the charging roller 12 is separated from the photosensitive drum 11 (due to fog development) in the first control section of the contact/separation determination mode executable by the control unit 30, a toner image is formed and the charging roller If the charging roller 12 is in contact with the photosensitive drum 11 (because fog development is not performed), no toner image is formed. become. In the second control section of the contact/separation determination mode that can be executed by the control unit 30, a toner image is not formed even when the charging roller 12 is separated from the photosensitive drum 11 (under the condition that fog development does not occur). Therefore, the amount of toner image necessary for determining the contact state of the charging roller 12 can be reduced.

Further, when the control unit determines that the charging roller is not in contact with the photosensitive drum, the display unit displays a notification requesting confirmation of the contact state of the charging roller with the photosensitive drum. can notice that an abnormality occurs in the contact state, so that it is possible to respond promptly.

In this embodiment, the duration of the first control section and the second control section are both 130 ms, for example, and the amount of toner consumed under these operating conditions is approximately 0.7 g.

This is almost half of the toner consumption of 1.4 g under the operating conditions at the time of the initial study of the present invention.

The operating conditions at the time of the initial study of the present invention differed from this embodiment only in that the charging voltage and the developing voltage in the second control section were -1200 V and -400 V, respectively. All operating conditions are the same. Further, specific contents of the operating conditions of each embodiment described here will be described later using Table 1.

Next, a mechanism for separating and contacting the charging roller 12 with the photosensitive drum 11 (separation and contact mechanism) in the process unit will be described. FIG. 4 is a diagram showing an example of a state in which the operator brings the charging roller 12 into contact with the photosensitive drum 11 when installing the image forming apparatus 10 or when replacing the process unit with a new one. Here, the charging roller 12 is brought into contact with the photosensitive drum 12 by pushing the knob 40 rightward in FIG. Here, the upper part of FIG. 4 shows the separated state in which the knob 40 is pulled out, and the lower part in FIG. 4 shows the contact state in which the knob 40 is pushed in as indicated by the arrow in the drawing.

Since the charging roller 12 is shipped separated from the photosensitive drum 11 as shown in FIG. 4, there is a gap between the charging roller 12 and the photosensitive drum 11. This can prevent deformation and deterioration of the surface elastic layer when the charging roller 12 is left for a long period of time.

On the other hand, when the charging roller 12 is brought into contact with the photosensitive drum 11, the knob 40 is pushed in as shown in the lower part of FIG. Here, as shown in the upper part of FIG. 4, the charging roller 12 and the cleaning roller 13 are held by a single bearing. have. When the knob 40 is pushed in while the charging roller 12 is separated, the locking portion 36a of the locking member 36 integrally formed with the knob 40 engaged with the claw 35 moves rightward in FIG. , and the engagement with the pawl 35 is released. At this time, the biasing member 37 that biases the bearing toward the photosensitive drum 11 pushes up the bearing, and the charging roller 12 abuts (contacts) the photosensitive drum 11 .

[Second embodiment]
Next, another embodiment of the invention will be described. In the above embodiment, the case where the present invention is applied when the image forming apparatus 10 is a monochrome image forming apparatus 10 has been described, but below, the case where the present invention is applied to a color image forming apparatus will be described. do.

FIG. 5 is a diagram corresponding to FIG. 1 in the previous embodiment when the present invention is applied when the image forming apparatus 10 is a color image forming apparatus 50. In FIG. Referring to FIG. 5, in this embodiment, color image forming apparatus 50 includes a yellow (Y) image forming section 60, a magenta (M) image forming section 70, and a cyan (C) image forming section. 80 and a black (K) image forming unit 90 .

The yellow (Y) image forming unit 60 includes a yellow (Y) photosensitive drum 61, a yellow (Y) charging roller 62, a yellow (Y) charging roller 62, and a Cleaning roller 63, yellow (Y) exposure unit 64, yellow (Y) development unit 65, yellow (Y) development roller 66, yellow (Y) developer (toner) 67, yellow (Y) static elimination unit 68, a yellow (Y) waste toner recovery unit 69a, and a yellow (Y) cleaning blade 69b.

Similarly, the magenta (M) image forming unit 70, the cyan (C) image forming unit 80, and the black (K) image forming unit 90 are formed by the respective color photosensitive drums 71, 81, and 91, respectively. charging rollers 72, 82 and 92 for each color; cleaning rollers 73, 83 and 93 for each color; exposure units 74, 84 and 94 for each color; developing units 75, 85 and 95 for each color; Developing rollers 76, 86, and 96 of respective colors, developers (toners) 77, 87, and 97 of respective colors, static elimination units 78, 88, and 98 of respective colors, and waste toner collecting portions of respective colors. 79a, 89a, and 99a, and respective colored cleaning blades 79b, 89b, and 99b.

The toner images of respective colors formed by the respective image forming units 60, 70, 80 and 90 are transferred to the intermediate transfer belt 54 via respective intermediate transfer rollers (intermediate transfer members) 55a to 55d, and are transferred onto the intermediate transfer belt 54. A color toner image is formed on the belt 54 . In order to transfer the image onto the intermediate transfer belt 54, the intermediate transfer rollers 55a to 55d are provided with intermediate transfer power supply control units 56a to 56d that apply bias voltages to the respective intermediate transfer rollers 55a to 55d.

The intermediate transfer belt 54 is wound around a drive roller 51a and a driven roller 51b, and a nip portion is formed between the drive roller 51a and the secondary transfer roller 52. A sheet (not shown) is sandwiched in the nip portion. While being conveyed, the color toner image on the surface of the intermediate transfer belt 54 is transferred onto the paper.

As shown in FIG. 5, the color image forming apparatus 50 is also provided with a control section 59 in the same manner as in FIG. Charging power supply control units 58a to 58d, intermediate transfer power supply control units 56a to 56d for controlling voltages applied to intermediate transfer rollers 55a to 55d, image sensor 53 for detecting toner images on intermediate transfer belt 54, and charging roller 62 , 72, 82 and 92 are connected to a display unit 34 or the like for displaying that the photosensitive drums 61, 71, 81 and 91 are not in contact with each other.

Here, the image forming units 60, 70, 80 and 90 are spaced apart from each other by, for example, 90 mm. , 80 and 90, the application time of the bias voltage to the photosensitive drums 61, 71, 81 and 91 is shorter than the photosensitive drum pitch/process speed. The process speed means the belt rotation speed of the intermediate transfer belt 54 .

That is, the control unit 59 sets the time for applying the bias voltage to each of the developing rollers 66, 76, 86 and 96 in the first control interval to be shorter than the pitch/process speed of the photosensitive drums 61, 71, 81 and 91. , the bias voltage is sequentially output to each of the developing rollers 66, 76, 86 and 96 at predetermined time intervals so as not to overlap and transfer onto the intermediate transfer belt 54. FIG.

With this configuration, even if all the charging rollers 62, 72, 82, and 92 of the image forming units 60, 70, 80, and 90 are separated from each other, Since the fog toner images are transferred without overlapping, the separated state of the charging rollers 62, 72, 82 and 92 can be reliably detected.

Next, the overall configuration of the color image forming apparatus 50 will be described. FIG. 6 is a diagram showing the overall configuration of the color image forming apparatus 50. As shown in FIG. As shown in FIG. 6, a yellow (Y) image forming unit 60, a magenta (M) image forming unit 70, a cyan (C) image forming unit 80, and a black (K) image forming unit 90 are respectively process units 60a, 70a, 80a and 90a, which are integrated together with developing units 65, 75, 85 and 95;

Also in the color image forming apparatus 50, the charging rollers 62, 72, 82 and 92 are brought into and out of contact with the respective photosensitive drums 61, 71, 81 and 91 in the respective process units 60a, 70a, 80a and 90a. It has a mechanism (detachment mechanism). The specific configuration is the same as that of the monochrome image forming apparatus 10 described with reference to FIG. 4, so description thereof will be omitted.

Next, in the color image forming apparatus 50, a method of detecting the contact/separation state (abnormality) between the charging rollers 62, 72, 82 and 92 of each color and the photosensitive drums 61, 71, 81 and 91 (separation/contact determination mode). will be explained. FIG. 7 is a diagram showing the control sequence of the first control section and the second control section in this method (first method), and is a diagram corresponding to FIG. 2 in the monochrome image forming apparatus 10. . Referring to FIG. 7, there are, from the top, on-off signals for the driving motors of the photosensitive drums 61, 71, 81 and 91 of the image forming units 60, 70, 80 and 90 of each color, black (K) On-Off signal for output to charging roller 92 of photosensitive drum 91 of image forming unit 90 of image forming unit 90, On-Off signal for output to developing roller 96, On-Off signal for output to charging roller 82 of image forming unit 80 for cyan (C) On-Off signal for output, On-Off signal for output to developing roller 86, On-Off signal for output to charging roller 72 of magenta (M) image forming section 70, and On for output to developing roller 76 A -Off signal, an On-Off signal for the output to the charging roller 62 of the yellow (Y) image forming unit 60, an On-Off signal for the output to the developing roller 66, and an output signal of the image sensor 53 are shown. there is Here, the first control section is indicated by a, and the second control section is indicated by b.

Referring to FIG. 7, the on-off signals of the driving motors of the photosensitive drums 61, 71, 81 and 91 of the image forming units 60, 70, 80 and 90 for each color are changed from the first control section to the second control section. It remains ON until the interval. The output to the charging roller 92 for black (K) is initially turned off and is 0 V, but is turned on in the first control section a, a predetermined negative voltage is applied, and in the second control section b Turns off when entering. The output to the developing roller 96 is initially turned off to 0 V, but is turned on in the first control section a, a predetermined negative voltage is applied, and in the second control section b, the reverse bias voltage is applied, and when the second control section b ends, the voltage is turned off and returns to 0V.

Output to the charging roller 82 and developing roller 86 of the image forming unit 80 for cyan (C), output to the charging roller 72 and developing roller 76 of the image forming unit 70 for magenta (M), and output to the image forming unit 60 for yellow (Y). The same applies to the output to the charging roller 62 and the developing roller 66 .

That is, in this embodiment, in the first control section a, the outputs to the charging rollers 62, 72, 82 and 92 of the image forming sections 60, 70, 80 and 90 for each color are and 96 are also turned on and a negative voltage is applied, and if the photosensitive drums 61, 71, 81 and 91 and the charging rollers 62, 72, 82 and 92 are separated from each other, fog development occurs. is satisfied, a fogging phenomenon occurs, and toner images are formed on the photosensitive drums 61 , 71 , 81 and 91 by the developing rollers 66 , 76 , 86 and 96 .

On the other hand, in the second control section b, the outputs to the charging rollers 62, 72, 82 and 92 are turned off, and the outputs to the developing rollers 66, 76, 86 and 96 are reverse biased. Even if the charging rollers 61, 71, 81 and 91 are separated from the charging rollers 62, 72, 82 and 92, fog development does not occur. , 71, 81 and 91.

In FIG. 7, as indicated by the dotted line for the charging roller 92 of black (K), in the second control section, the power may not be turned off, but the voltage may be lower than the discharge start voltage at which the photosensitive drum 91 is not charged. .

In addition, as indicated by dotted lines, the voltage applied in the second control section b is also applied to the outputs of the charging rollers 62, 72, and 82 for cyan, magenta, and yellow. It may be set to a voltage lower than the starting voltage. By doing so, it is possible to prevent the photosensitive drums 61, 71 and 81 from being charged in the second control section without turning off the power.

At the bottom of FIG. 7, the output of image sensor 53 is shown. Since the image is not normally detected, the signal is High. A low signal is output because a toner image is generated by . Here, the charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96 are separated from each other in the four image forming sections 60, 70, 80 and 90. The low signals of black (K), cyan (C), magenta (M), and yellow (Y) when an image is generated are indicated by dotted lines in the figure. Since the image forming units 60, 70, 80 and 90 for each color are formed at regular time intervals, the outputs of the image density sensor 53 due to fog development are also formed at intervals for each color.

Here, the image forming sections 60, 70, 80 and 90 of each color are illustrated so that the first control section (a) is shorter than the second control section (b), which is the same as in FIG. 2, the distance from the image forming units 60, 70, 80, and 90 of each color to the image sensor 53 is long, so the time required for the toner image formed by fogging to reach the image sensor 53 is long. This is to prevent the fog development from using a large amount of toner.

Here, for each color, the output to the charging roller and the output to the developing roller are shown in the first section and the second section, and the case where the image sensor 53 detects them individually will be described. However, the image sensor 53 may be provided in each of the four image forming units 60 , 70 , 80 and 90 that constitute the color image forming apparatus 50 .

As described above, in the color image forming apparatus 50, the charging rollers 62, 72, 82, and 92 each including the plurality of photosensitive drums 61, 71, 81, and 91 are individually included in order to output images of a plurality of colors. , development rollers 66, 76, 86 and 96, and an intermediate transfer belt 54 (intermediate transfer member) onto which the toner images formed on the respective photosensitive drums 61, 71, 81 and 91 are transferred, The controller 59 controls the charging rollers 62, 72, 82 and 92 and the developing roller 66, 92 based on the detection result of the toner image by the image sensor 53 arranged to detect the toner image on the intermediate transfer belt 54. A contact/separation state with respect to the photosensitive drums 61, 71, 81 and 91 in a plurality of groups 76, 86 and 96 can be determined.

Further, in the color image forming apparatus 50, a set of a plurality of charging rollers 62, 72, 82 and 92 each including a plurality of photosensitive drums 61, 71, 81 and 91 and developing rollers 66, 76, 86 and 96 A predetermined voltage is applied in order to form an image using . It varies depending on the set of the charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96. Therefore, by measuring and comparing the time from the start of application of a predetermined voltage until the image sensor 53 detects a toner image (which is formed when fog development is performed), the number of the photosensitive drums 61 and 71 can be determined. , 81 and 91, respectively, can be specified.

Next, a method of determining the contact state of the charging rollers 62, 72, 82 and 92 in the color image forming apparatus 50 (separation/contact determination mode) will be described. FIG. 8 is a flowchart showing a method for determining the contact state of the charging rollers in the color image forming apparatus 50. As shown in FIG.

Referring to FIG. 8, the CPU of the control unit 59 first rotates a drive motor (not shown) to drive the i-th one of the four Y, M, C and K photosensitive drums 61, 71, 81 and 91. th (where i = 1, i is a numerical value (variable) assigned to each color to identify Y, M, C, and K for control by the program. In the case of this embodiment, 1 is Y , 2 for M, 3 for C, and 4 for K) are rotated (S21). A first charging bias voltage is applied to the i-th charging roller, and a first developing bias voltage is applied to the i-th developing rollers 66, 76, 86 and 96 (S22). After waiting for the first time to elapse (S23), when the elapse of the first time (Y in S23), the second charging bias voltage is applied to the i-th charging roller and the second developing bias is applied to the i-th developing roller. A voltage is applied (S24).

Next, it is determined whether the image sensor 53 has detected an image having a density correlated with the first time or the first charging bias (i-th) (signal Low) (S25).

When the image density sensor 53 does not detect an image (signal Low) in S25 (N in S25), it is determined whether or not the second time has elapsed (S26). In S26, if the second time has passed, it is determined whether the last charging unit has ended (S27).

In S26, when the second time has not elapsed (N in S26), the process returns to S24. In S26, if the second time has passed (Y in S26), it is determined whether or not the last charging unit has finished (S27). When the last charging unit is not finished in S27 (N in S27), i=i+1 is set (S29) and the process returns to S22.

In S25, when the image sensor 53 detects an image (signal Low) having a density correlated with the first time or the first charging bias (i-th), Y in S25, the charging roller is not in contact, Then, it is determined that the i-th charging roller is not in contact, and is displayed on the display unit 34 (S30). It is determined whether or not the last (i=4) charging unit has finished (S31). The application to the developing roller is stopped, and the rotation of the drive motor is also stopped (S32). In S31, if the last (i=4) charging unit has not completed (N in S31), i=i+1 (S33) and the process returns to S22, and this is repeated until i=4.

Here, as in the previous embodiment, the first time is the charging rollers 62, 72 necessary for forming band-like images on the photosensitive drums 61, 71, 81, and 91 by fog development. , 82 and 92. Note that the exposure unit 14 is not operated in this embodiment as well as in the first embodiment.

As described above, in this embodiment, in the color image forming apparatus 50, the developing bias voltage and the charging bias voltage are controlled to create the first control section for causing fog development, and the charging rollers 62, 72, The image sensor 53 detects a fog image that is formed only when 82 and 92 are separated. This makes it possible to confirm that the charging rollers 62, 72, 82 and 92 are in a separated (trouble=abnormal) state.

That is, without providing an ammeter or a dedicated sensor, by executing the contact/separation determination mode using the existing image sensor 53, the photosensitive drums 61, 71, 81 of the charging rollers 62, 72, 82 and 92 and 91 can be effectively determined.

Next, a second method (another contact/separation determination mode) for detecting an abnormality in the color image forming apparatus 50 will be described. FIG. 9 is a diagram showing a control sequence in the second method of detecting an abnormality in color image forming apparatus 50. As shown in FIG. Referring to FIG. 9, there are, from the top, on-off signals for the driving motors of the photosensitive drums 81 and 91 of the two color image forming units (cyan (C) and black (K)) 80 and 90. , an on-off signal for output to the charging roller 92 of the image forming unit 90 for black (K), an on-off signal for output to the developing roller 96, and an on-off signal for output to the charging roller 82 of the image forming unit 80 for cyan (C). An output on-off signal and an output on-off signal to the developing roller 86 are shown. Again, the first control interval is denoted by a and the second control interval by b.

Referring to FIG. 9, the on-off signal for the driving motors of photosensitive drums 81 and 91 is on from the first control section to the second control section. The output of black (K) to the charging roller 92 is initially off, but is turned on in the first control section a, a predetermined negative voltage is applied, and the output is off in the second control section b. do. The output to the developing roller 96 is initially 0 V, but is turned ON in the first control section a, a predetermined negative voltage is applied, and in the second control section b, the reverse bias voltage is positive. is applied, and when the second control section b ends, the voltage is turned off to return to 0V.

The output of the charging roller 82 of the image forming unit 80 for cyan (C) and the developing roller 96 in the first control section a is longer than the output of the charging roller 92 for black (K), and the output of the second control section b The output is shorter than that of the charging roller 92 for black (K).

That is, in this embodiment, since the length of time of the first control section is changed for each image forming section of each color (here, two colors of black and cyan), the time for fog development is Different for each color. As a result, if the time required for the image sensor 53 to detect the fogging image is known, it is possible to know which color of the charging roller of the image forming unit is separated.

That is, according to this embodiment, the time of the first control section is individually set for a plurality of pairs of charging rollers and developing rollers, and the toner image detected by the image sensor 53 (fogging development is performed). By comparing the detection time of each of the first control sections set individually with the detection time of the first control section formed when the charging A set of rollers and developer rollers can be specified. In other words, the state of contact with the photosensitive drums 61, 71, 81 and 91 in sets of a plurality of charging rollers 62, 72, 82 and 92 and developing rollers 66, 76, 86 and 96 can be determined.

In the above example, the length of time of the first control section is changed for each image forming section of each color.
In the first control section, the absolute value of the voltage applied to the developing roller may be controlled to be smaller than that at the time of image output for a plurality of sets of charging roller and developing roller.

By doing so, the density of the toner image formed by fogging development can be reduced, and the amount of toner consumed by fogging development can be reduced (required minimum).

Further, in the first control section, voltages applied to the plurality of sets of charging rollers and developing rollers are applied to the respective developing rollers at different rates compared to the voltage at the time of image output, and are detected by the image sensor. A combination of a charging roller and a developing roller that is in an abnormal contact state with the photosensitive drum may be identified by comparing the magnitude of the detection value and the voltage applied to the developing roller.

By doing so, since the voltage applied to each developing roller is different, the density of the toner image formed by each developing roller due to fog development is different. Therefore, it becomes possible to accurately identify the combination of the charging roller and the developing roller that is in an abnormal contact state with the photosensitive drum.

Further, when the control unit determines that the charging roller is not in contact with the photosensitive drum, the display unit displays the photosensitive drum of the charging roller of the process unit that has determined that the charging roller is not in contact with the photosensitive drum. Since the notification is displayed so as to confirm the state of contact with the body drum, the operator can recognize the abnormal process unit and can promptly respond.

Next, a third method (another separation determination mode) for detecting contact separation in the color image forming apparatus 50 will be described. FIG. 10 is a diagram showing a control sequence in the third method of detecting abnormality in color image forming apparatus 50. As shown in FIG.

Referring to FIG. 10, there are, from the top, on-off signals for the driving motors of the photosensitive drums 81 and 91 of the two color image forming units (cyan (C) and black (K)) 80 and 90. , an on-off signal for output to the charging roller 92 of the image forming unit 90 for black (K), an on-off signal for output to the developing roller 96, and an on-off signal for output to the charging roller 82 of the image forming unit 80 for cyan (C). An output on-off signal and an output on-off signal to the developing roller 86 are shown. Again, the first control interval is denoted by a and the second control interval by b.

In FIG. 10, the on-off signal for the driving motors of the photosensitive drums 81 and 91 is on from the first control section to the second control section. The output of black (K) to the charging roller 92 is initially off, but is turned on in the first control section a, a predetermined voltage is applied, and is turned off in the second control section b. Next, it enters the first control section a for the second time, turns it on again, applies a predetermined voltage, and then enters the second control section b for the second time, and turns it off.

In addition, the applied voltage and time of the first control section a are substantially the same for the two times, the time of the second control section b of the first time is substantially the same as that of the first control section a, and the time of the second control section b is substantially the same as that of the first control section a. is longer than the first time.

On the other hand, the output of the developing roller 96 is initially off, but is turned on in the first control section a and a predetermined voltage is applied, and in the second control section b, the reverse bias voltage is applied. Next, it enters the first control section a for the second time, turns ON again, applies a predetermined voltage, and then enters the second control section b for the second time, applies the reverse bias voltage, and performs the second control. It turns off when the interval b ends. That is, in this embodiment, the first control section a and the second control section b are repeated twice.

In addition, the applied voltage and time of the first control section a are substantially the same for the two times, the time of the second control section b of the first time is substantially the same as that of the first control section a, and the time of the second control section b is substantially the same as that of the first control section a. is longer than the first time.

Output voltages to the charging roller 82 and developing roller 86 of the cyan (C) image forming unit 80 are shown below.

Here, the output to the charging roller 82 is initially off, but is turned on in the first control section a, a predetermined voltage is applied, and is turned off again in the second control section b. The output voltage to the developing roller 86 is initially off, but is turned on in the first control section a and a predetermined voltage is applied, and in the second control section b, the reverse bias voltage is applied. be.

Here, the length of the first control section a of the cyan (C) charging roller 82 and the developing roller 86 is equal to the length of the first control section a of the black (K) charging roller 92 and the developing roller 96. It is about twice as long and the control interval is not repeated as in the case of black (K) charge roller 92 and developer roller 96 .

That is, in this embodiment, the time of the first control section and the time of the second control section are repeated, or the time of the first control section and the time of the second control section are repeated only once. Since the ratio between the time of the first control section and the time of the second control section is changed for each of the image forming sections 60, 70, 80 and 90 of each color, the time for fog development, Patterns are different for each color. As a result, if the time and pattern at which the image density sensor 53 detects the fogging image are known, which colors of the charging rollers 62, 72, 82, and 92 of the image forming units 60, 70, 80, and 90 are apart? I understand.

That is, in this embodiment, the first control section a and the second control section are set for the sets of the charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96. By performing a plurality of operations, it is possible to determine the state of contact with the photosensitive drums 61, 71, 81 and 91 in the sets of the plurality of charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96. .

Note that the absolute value of the voltage applied in the first control section may be smaller than that during image output. By doing so, the amount of toner flowing out can be suppressed. The operating conditions in this case are indicated by condition F in Table 1.

Also, the voltage applied in the first control section to the set of the plurality of charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96 differs from the voltage at the time of image output. , the contact state with respect to the photosensitive drums 61, 71, 81 and 91 in the sets of the charging rollers 62, 72, 82 and 92 and the developing rollers 66, 76, 86 and 96 is determined. good too.

Next, the details of the operating conditions and the amount of toner consumed under the operating conditions in the above embodiment will be described. Table 1 is a table showing operating conditions and the like.

Here, the operating condition A corresponds to the embodiment at the time of the initial study of the present invention, and the operating condition B corresponds to the control condition described at the beginning, which was described in the monochrome image forming apparatus 10 described above. It is. Operating condition C corresponds to the conditions described later, and operating conditions D to F correspond to the above-described embodiments, respectively.

The invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiments are merely examples and should not be construed as limiting. All modifications and changes that fall within the equivalent scope of the claims of the present invention are within the scope of the present invention.

The present invention executes a contact/separation determination mode that determines the contact/separation state between the photosensitive drum and the charging roller using fogging development in which a toner image is formed when the photosensitive drum and charging roller are in a non-contact state. Therefore, it is useful as an image forming apparatus having a charging roller that can be separated from and contacted with the photosensitive drum by a separation mechanism.

10 Image forming device 11 Photoreceptor drum 12 Charging roller 13 Cleaning roller 14 Exposure unit 15 Development unit 16 Development roller 17 Developer (toner)
18 transfer unit 19 static elimination unit 20 waste toner recovery unit 21 cleaning blades 22, 53 image sensor 23 charging power supply 24 development power supply 25 transfer power supply 30, 59 control unit 34 display unit 38 paper 50 color image forming device 54 intermediate transfer belt 55 intermediate transfer roller 56 intermediate transfer power supply 60 yellow (Y) image forming unit 70 magenta (M) image forming unit 80 cyan (C) image forming unit 90 black (K) image forming unit

Claims (13)

a photoreceptor drum; and a charging roller that charges the surface of the photoreceptor drum and is separable from and contactable to the photoreceptor by a contact and separation mechanism;
a developing section having a developing roller for forming a toner image on the surface of the photosensitive drum;
An image forming apparatus comprising an image sensor for detecting a toner image formed on the surface of the photosensitive drum, and a controller,
The controller forms a toner image on the photosensitive drum if the contact state of the charging roller with the photosensitive drum is abnormal, and does not form the toner image if the contact state of the charging roller is normal. capable of executing a contact/separation determination mode having a first control section and a second control section in which a toner image is not formed on the photosensitive drum regardless of the contact state of the charging roller;
The image forming apparatus, wherein the control unit determines a contact state of the charging roller with the photosensitive drum based on a detection result of the image sensor in the first control section. a charging power supply that applies a predetermined voltage to the charging roller;
a developing power supply that applies a predetermined voltage to the developing roller,
The control unit
In the first control section, a predetermined voltage that is the same condition as in image formation is applied to the charging roller and the developing roller,
In the second control section, a voltage having a polarity opposite to that during image formation is applied to the developing roller, and no voltage is applied to the charging roller, or a voltage lower than the discharge start voltage of the charging roller is applied. 2. The image forming apparatus according to claim 1, wherein: further comprising a transfer member for transferring the toner image on the photoreceptor drum to a sheet and a transfer power supply for the transfer member;
3. The image forming apparatus according to claim 1, wherein, in the first control section, the control section applies a voltage having a polarity different from that during image formation to the transfer member. 4. The image according to any one of claims 1 to 3, wherein the control unit controls the time of the first control section to be shorter than the time of the second control section. forming device. The image forming device includes a color image forming device that outputs images of a plurality of colors,
In order to output images of a plurality of colors, the color image forming apparatus includes a plurality of pairs of charging rollers and developing rollers, each of which includes a photosensitive drum, and a toner image formed on each of the photosensitive drums. an intermediate transfer member to be transferred;
The controller controls contact of the set of the plurality of charging rollers and the developing roller with the photosensitive drum based on the detection result of the image sensor arranged to detect the toner image on the intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein the state is determined. The controller measures and compares the time from the start of application of a predetermined voltage to the detection of the toner image by the density sensor to the sets of the plurality of charging rollers and the developing rollers, thereby determining the photosensitive toner image. 6. The image forming apparatus according to claim 5, wherein a set of the charging roller and the developing roller having an abnormal contact state with the body drum is specified. The control unit individually sets the time of the first control section for each of the plurality of sets of charging rollers and developing rollers, and sets the detection time of the toner image detected by the image sensor and each of the first control sections. 7. The image forming apparatus according to claim 5, wherein a pair of the charging roller and the developing roller having an abnormal contact state with the photosensitive drum is specified by comparing the times of the control sections. In the first control section, the control unit controls the set of the plurality of charging rollers and the developing roller so that the absolute value of the voltage applied to the developing roller is smaller than that at the time of image output. The image forming apparatus according to any one of claims 5 to 7, characterized by: In the first control section, the control unit applies voltages to the plurality of sets of the charging rollers and the developing rollers at different rates compared to the voltage at the time of image output. By comparing the magnitude of the detection value detected by the image sensor and the voltage applied to the developing roller, a set of the charging roller and the developing roller that is in an abnormal contact state with the photosensitive drum is identified. 6. The image forming apparatus according to claim 5. The control unit performs a plurality of the first control sections and the second control sections for the sets of the plurality of charging rollers and the developing rollers, thereby controlling the plurality of charging rollers and the developing rollers. 6. The image forming apparatus according to claim 5, wherein the state of contact with the photoreceptor drum in each group is determined. The photosensitive drum and the charging roller constitute a process unit,
At the time of replacement of the process unit, the control unit, based on the presence or absence of a toner image on the surface of the photosensitive drum in the first control section and the second control section, detected by the image sensor, The image forming apparatus according to any one of claims 1 to 10, wherein the contact state of the charging roller to the photosensitive drum is determined. further comprising a display,
When the control unit determines that the charging roller is not in contact with the photosensitive drum, the display unit displays a notification requesting confirmation of the contact state of the charging roller with the photosensitive drum. 12. The image forming apparatus according to claim 11, wherein: further comprising a display,
When the controller determines that the charging roller is not in contact with the photoreceptor drum, the process unit determines that the charging roller is not in contact with the photoreceptor drum by displaying the display unit. 12. The image forming apparatus according to claim 11, wherein a notification is displayed so as to confirm the contact state of the charging roller with the photosensitive drum.

Images