JPH037963A - Image forming device - Google Patents

Abstract

PURPOSE:To detect the cause of image unevenneass from a position itself by detecting surface potential of a photosensitive body and image density each with sensors and judging whether operation state of an electrifying charger and a developing device is good or not, based on the detected results. CONSTITUTION:In the periphery of the photosensitive body drum 1, a surface potential sensor 4 is provided in a range X3 between an exposing point X2 from an optical system 2 and a developing range X4 of the developing device 5, and further an image density sensor 7 is provided in a range X6 between a transferring range X5 of a transferring charger 6 and a cleaning device 8. The output from the surface potential sensor 4 is compared with each reference voltage Vh and Vl at comparators 63 and 64, and output from an image density sensor 7 is compared with each reference voltage VH and HL each at comparators 61 and 62. The output from the comparators 61 to 64 are led to a CPU 60 and, as a result, since whether the operation state of the electrifying charger 3, the developing device 5, and the transferring charger 6 is good or not is judged, action can be taken by servicing persons, etc., speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic recording type image forming apparatus such as a copying machine, and more specifically to a device for detecting the cause of image defects.

[Prior art]

In an electrostatic recording type image forming apparatus such as a copying machine, if the charge wire of the charger that charges the photoconductor becomes contaminated with toner etc., the charging ability will decrease or charging unevenness will occur, resulting in a decrease in image density or This causes image unevenness. Therefore, Japanese Unexamined Patent Publication No. 177571/1983 proposes a device that is provided with a sensor for detecting the surface potential of a photoconductor and that cleans the wire when uneven charging is detected.

[Problem to be solved by the invention]

However, in an electrostatic recording type image forming apparatus, the cause of unevenness on the formed image is not only the above-mentioned trouble around the charger, but also other troubles such as abnormalities in the developing device. When unevenness occurs on an image (1), even if it is a simple malfunction, the user does not know where the cause of the trouble is. Therefore, it was difficult to know what to check, and it was impossible to restore the device to its normal state unless a service person was called. Furthermore, for service personnel, finding the cause requires a great deal of effort and time.

The present invention has been made in view of the above circumstances, and by detecting the surface potential and image density, the cause of image unevenness can be detected in the device itself, allowing service personnel and the like to take prompt action. The purpose is to provide image forming devices.

[Means to solve the problem]

An image forming apparatus according to the present invention includes a developing device that develops an electrostatic latent image formed by exposure on a photoreceptor charged with a charger with toner, and a developing device that develops an electrostatic latent image formed by exposure on a photoreceptor charged with an electrostatic charger, and a surface potential of the charged photoreceptor. An image forming apparatus comprising: a surface potential sensor for detecting a surface potential; a latent image forming means for forming an electrostatic latent image with a predetermined exposure amount on the photoreceptor; and an electrostatic latent image formed by the latent image forming means. a density sensor for detecting the density of a toner image developed by the developing device; and means for determining whether the operating state of the charger and the developing device is good or bad based on the detection results of the surface potential sensor and the density sensor. A transfer charger for transferring the developed toner image onto a transfer body, a transfer density sensor for detecting the density of the toner image transferred by the transfer charger, the surface potential sensor, and the density sensor. and means for determining whether the operating states of the electrostatic charger, the developing device, and the transfer charger are good or bad based on the detection results of the transfer density sensor.

[Effect]

In the first invention, a latent image is formed on the photoreceptor by a predetermined exposure amount, and the density of the toner image developed from the latent image is detected by a density sensor.

Based on this detection result and the detection result of the surface potential of the photoreceptor, it is determined whether the operating states of the charger and the developing device are good or bad. For example, if the surface potential is normal and the density is abnormal, it is determined that the developing device is abnormal.

Further, in the second invention, in addition to the above, the transfer density of the transferred toner image is detected by a transfer density sensor.

Based on this detection result and the detection results of the two sensors, it is determined whether the operating states of the charger, developer, and transfer charger are good or bad. For example, if the surface potential and toner density are normal and the transfer density is abnormal, it is determined that the transfer charger is abnormal.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus according to the present invention applied to a copying machine, and a block diagram of a control system. In this copying operation, first, while the photoreceptor drum 1 is rotating in the direction of arrow a, a constant charge is applied to the surface of the photoreceptor drum 1 by discharging from the charging charger 3. Next, the scanner 24 having the exposure lamp 21 of the optical system 2 scans in the direction indicated by the arrow and irradiates light onto the document placed on the document table glass 10, and the reflected light is reflected by the mirrors 22a to 22d. The surface of the photosensitive drum 1 is exposed from the exposure point Xz through the lens 23, and an electrostatic latent image corresponding to the original image is formed.

A predetermined density (
A rectangular reference pattern 12 having halftones is provided.

The formed electrostatic latent image is supplied with toner and visualized in a developing area X4, which is a portion facing the developing device 5, and a toner image reproducing the original image is formed.

On the other hand, copy paper is stored in a paper feed cassette 31 and is conveyed to the timing roller pair 11 at a predetermined timing. The conveyed copy paper is conveyed by a pair of timing rollers 11 to a portion facing the transfer charger 6 (transfer area XS) at the timing with the toner image on the photoreceptor drum 1. After the toner image is transferred onto the copy paper, the copy paper is conveyed by a conveyor 32 to a fixing device 30, and the toner image is melted and fixed onto the copy paper.

After the toner image is transferred, the residual toner on the surface of the photosensitive drum 1 is scraped off by a cleaning device 8, and the residual charge is further erased by light irradiation from an eraser lamp 9.
Ready for the next development.

FIG. 2 is an explanatory diagram of the operation panel of the copying machine.

As shown in the figure, the operation panel 100 includes a numeric keypad group 102 for setting the number of copies, etc., a print key 101 for instructing to start printing, an interrupt key 10 for instructing interrupt copying, a clear/stop key 107, and a copy paper size. Paper selection key 109 for selecting the copy density, Density up/down keys 103, 104 for setting the copy density, Copy magnification setting keys 105, 106, Display section 110 for displaying the number of multi-copy sheets etc. in segments, Displaying abnormal parts of the copying machine in segments. Various keys and display parts are arranged, such as an abnormality display part 111 to indicate that a serviceman needs to perform recovery work from an abnormality, and a serviceman call display part 112.

The abnormality display section 111 has a 4-digit, 7-segment display, and normally displays the copying magnification, and when an abnormality occurs, displays the abnormal region with a 2-digit code. For example, C1 is the charging charger 3, C2 is the developing device 5, C3 is the transfer charger 6, and C4 is the fixing device 30, and their combinations are also displayed.

Note that when the serviceman call display section 112 lights up,
Copying operations are automatically prohibited.

Next, a mechanism for detecting image unevenness, which is the gist of the present invention, will be explained. First, two sensors are provided around the photosensitive drum 1, namely a surface potential sensor 4 and an image density sensor 7. The surface potential sensor 4 is located in an area X3 between the exposure point X2 of the photosensitive drum 1 and the developing area X4 of the developing device 5.
Furthermore, the image density sensor 7 is located in the transfer area X of the transfer charger 6.

and the cleaning device 8, respectively.

The surface potential sensor 4 is known, for example, from Japanese Patent Application Laid-Open No. 63-309978, and a detailed explanation thereof will be omitted, but the general idea is that a voltage of a predetermined frequency is applied to the surface of the photoreceptor drum 1, and the voltage is returned. The electric potential is detected by measuring the amount of change in vibration. The image density sensor 7 uses a reflection type photosensor having a light emitting part 7a and a light receiving part 7b. By detecting it, the amount of toner adhesion, that is, the image density, is detected in an analog manner as the amount of reflected light, and the amount of received light is converted into a voltage and output.

The surface potential sensor 4 and the image density sensor 7 are attached to a wire 43 or 73 stretched between a driving pulley 41 and a driven pulley 42, or between a driving pulley 71 and a driven pulley 72, as shown in the block diagram of FIG. By transmitting the driving force of the motor 44 or 74 to the drive pulley 41 or 71 via the gears 45 and 46 or 75 and 76, the axis of each detection area X3 or X6 of the photosensitive drum 1 is transmitted. The surface potential or image density is detected while moving over the entire length in the longitudinal direction.

Switches 47 and 48 or 77 and 7 are provided near both ends of the photosensitive drum 1 in the movement range of each sensor 4 and 7, respectively.
For example, if the surface potential sensor 4 or the image density sensor 7 is currently moving in the direction of the arrow C1 or e, they can be moved to the end of the detection area by turning on the switch 47 or 77, respectively. It is detected that the motor 44 or 74 has reached this point, and the driving of the motor 44 or 74 is stopped. When the next detection is performed, the motor 44 or 74 is rotated in the opposite direction, the sensor 4 or 7 is moved in the direction of the arrow d or f, and the switch 48 or 7 is turned on. The motor is stopped.

The output of the surface potential sensor 4 is applied to comparators 63 and 64 via a surface potential detection circuit 66, and is compared with a reference voltage vh in the converter rotor 3 and with a reference voltage Vl in the comparator 64, and the detected voltage is greater than vh. or if it is smaller than Vl, that is, if it exceeds the upper limit value of the appropriate surface potential or falls below the lower limit value, the CPU 60
A signal is output to.

Similarly, the output of the image density sensor 7 is given to comparators 61 and 62, and the detected voltages are reference voltages VH and 62 respectively determined for upper and lower limits of appropriate image density in a halftone toner image, which will be described later. If it exceeds or falls below VL, a signal is output to the CPU 60.

The switches 47, 48 and 77.degree. 78 are connected to the input side of the CPU 60, and the motors 44 and 74 are connected to the output side of the CPU 60 via a drive circuit (not shown).

Further, a control circuit 65 is connected to the output side of the CPU 60 to control the driving of a cleaning device 80 that cleans the charge wire 88 of the charger 3.

FIG. 4 is a configuration diagram of the cleaning device 80.
is stretched between the driving pulley 82 and the driven pulley 83. A running member 8 that includes cleaning members 86 and 87 that hold a charge wire 88 in a gripping manner on this drive rope 81
5 is supported. The drive pulley 82 is rotated by a motor 84, which causes the running member 85 to rotate.
The charge wire 88 is moved in the direction in which the charge wire 88 is stretched, and the wire is cleaned by cleaning members 86 and 87.

Next, the control procedure of the apparatus of the present invention constructed as described above will be explained using the flowcharts shown in FIGS. 5 to 8.

FIG. 5 is a routine showing the main program. First, initialization in step S1 is always performed when the power is turned on, and the contents of each memory, register, and flag are set to initial values. When the initial settings are completed, input processing such as the number of copies, magnification, paper size, etc. is performed by operating each key on the operation panel 100 (step S2). When the print key 101 is turned on (step S3), a copying operation is started (step S4).

In the next step S5, a number indicating the number of copies is decremented, and a variable P for detecting image unevenness is incremented.

The copying operation is continued until the set number reaches O (step S6), and when the set number reaches O, it is then determined whether P is greater than 500 (step S7). If the variable P is greater than 500, the process proceeds to the density unevenness detection routine shown in FIG. 6 (step S8); if it is small, the process is terminated. That is, in this embodiment, image unevenness is detected every 500 copies.

FIG. 6 shows the density unevenness detection routine in step S8. First, the charger 3 and exposure lamp 21 are turned on, and the photosensitive drum 1 and developing device 5 are driven (step 511). At this time, the scanner 24 is at the home position outside the document scanning area, and is located directly below the reference pattern 12 of a predetermined density provided on the home position side of the document glass 10, and the light amount of the exposure lamp 21 is 1 at a predetermined level on which a halftone image is formed.

Also, at this point, turn on the timer (step 512),
When 0.8 sec has elapsed, the charger 3 and the exposure lamp 21 are turned off, the photosensitive drum 1 and the developing device 5 are stopped, and the timer is reset (step 51).
3,514), during this 0.8 sec, in this copying machine, the area charged at point xI on the photosensitive drum 1 shown in FIG. This is the time to reach area X.

As a result, a halftone toner image is formed in the detection area of the image density sensor 7, and the image density sensor 7 is moved to detect the image density (step 515). 9th
The figure is a graph showing an example of a change in the output voltage of the image density sensor 7, where the vertical axis shows the output voltage of the sensor, the horizontal axis shows the detection position of the sensor in the longitudinal direction of the photosensitive drum 1, and L is the photosensitive drum 1. This is the length of the range that can be used for image formation on the body drum 1. If the halftone image is uniform, the output voltage is constant, but as shown in the figure, if there is a dark area in some areas, the output voltage will be lower than the reference voltage VL, and if it is thin, the output voltage will be higher than the reference voltage V)I. In other words, if the output voltage is within the range of the reference voltage V)I-VL, the comparators 61 and 62
Since there is no output, it is stored as having no density unevenness. Also, if it is outside the range, there is an output from comparators 61 and 62, so
This output is stored as having density unevenness (Step 5
16).

Next, when the image density sensor 7 moves to the end of the photoreceptor drum 1 and turns on the switch 77 or 78, after stopping the movement of the image density sensor 7 (steer knob S17, 518
), then detection of charging unevenness is performed.

FIG. 7 shows the charging unevenness detection routine in step S9. First, the charger 3 is turned on and the photosensitive drum 1 is driven (step 521).

At this time, the exposure lamp 21 is not turned on. At this point, the timer is turned on (step 522) and the process waits for 0.2 seconds (step 523). This is the time required for the charged area to reach the measurement position of the surface potential sensor 4.

Next, the surface potential sensor 4 is moved to detect the surface potential of the photosensitive drum 1 (step 524).

FIG. 10 shows an example of changes in the output voltage of the surface potential. Similar to FIG. 9, the horizontal axis represents the detection position of the sensor in the longitudinal direction of the photosensitive drum 1, and the vertical axis represents the surface potential. Similar to the density unevenness described above, the output voltage is at the reference potential vh~
(2) If it is within the range of β, there is no output from the comparators 63 and 64 and it is stored as there being no uneven charging. If it is outside the range, since there are outputs from the comparators 63 and 64, it is stored as uneven charging (step 525).

When the surface potential sensor 4 moves to the end of the photoreceptor drum 1 and turns on the switch 47 or 48, the movement of the surface potential sensor 4 is stopped, the charger 3 is turned off, and the photoreceptor drum 1 is driven. After stopping (steps S26, 527), the process then moves to the abnormality processing routine of step SIO.

FIG. 8 is a flowchart showing the contents of the abnormality processing routine in step SIO. First, when it is determined in step S31 that there is uneven charging, it means that the charger 2 is contaminated, so the cleaning device 80 charges the charger 2. Automatic cleaning of the wire 88 is performed (step 532).

On the other hand, if it is determined that there is no charging unevenness, the next step is to determine whether or not there is density unevenness (step 533). If there is a '114 degree unevenness, the operation panel 10 indicates that there is an abnormality in the developing device 5.
"02" is displayed on the developer abnormality display section 111 of 0, and the serviceman call display section 112 is turned on (
Step 534).

After that, if there is no density unevenness or if automatic cleaning of the charger 3 is performed, step S3
At step 5, the variable P is reset and the process ends.

In other words, in the apparatus of the present invention, an image defect is first detected by the image density sensor 7, but at this point it is either due to a charging failure by the charger 3 or due to an abnormality in other parts such as the developing unit 5 or the optical system 2. I can't decide what it is. Then, by detecting the surface potential with the surface potential sensor 4, if it is normal, it can be determined that there is an abnormality in the developing device 5, and if it is abnormal, it can be determined that a charging failure has occurred, and the charge wire 88 The purpose of this work is to clean the area.

Note that in this embodiment, charging unevenness is detected regardless of whether or not density unevenness is detected, but the present invention is not limited to this. Detection of charging unevenness may be performed only in this case. Furthermore, since there is no need to detect density unevenness if charging unevenness occurs, density unevenness may be detected only when there is no charging unevenness. By doing so, the detection time when there is no density unevenness or charging unevenness can be shortened.

Further, the detection of charging unevenness and the detection of density unevenness may be performed simultaneously, and the detection time can be further shortened.

Further, in this embodiment, if there is an abnormality in the developing device, this is displayed, but instead of this, image formation may be prohibited.

Next, other embodiments of the present invention will be described.

In the above-described embodiment, a defect in the charger 3 or the developing device 5 was considered as a cause of image unevenness, but a defect in the transfer charger 6 may also be considered as another cause of image unevenness. That is, if the transfer charger 6 is dirty, the transfer efficiency in that area may decrease and the image may become lighter. Therefore, in this embodiment, the density unevenness of the paper after transfer is detected, and this detection result is taken into consideration in addition to the two detection results described above to determine which of the charger 3, the developing device 5, and the transfer charger 6 is defective. Identify.

In the explanation of the structure and operation of this embodiment, explanations of parts common to the previous embodiments will be omitted. FIG. 11 is a cross-sectional view showing a schematic configuration when an image forming apparatus according to another embodiment is applied to a copying machine, and a block diagram of a control system.

In the figure, an image density sensor 15 is provided above the conveyor 32 to detect the image density of the copy paper after transfer. The image density sensor 15 has a similar structure to the image density sensor 7 that detects the image density of the photosensitive drum 1, and uses a reflective photosensor having a light emitting section 15a and a light receiving section 15b. Similarly, it is movable by being driven by a motor 154 in a direction perpendicular to the conveyance direction of the copy paper using a mechanism as shown in FIGS. 3 and 4.

Switches 157 and 158 are provided at both ends of the detection area.

The detection voltage of the image density sensor 15 is applied to comparators 67 and 68. If the detected voltage exceeds or falls below reference voltages Vll and VL determined for the upper and lower limits of appropriate image density in a halftone toner image, respectively, which will be described later, a signal is output to the CPU 60. .

On the input side of the CPLI 60 are the switches 47, 48 .
77, 78 and 157, 158 and other inputs are connected to it, and the motors 44, 74 and 154 and other outputs are connected to the output side via a drive circuit (not shown).

Further, a control circuit 65 is connected to the output side of the CPU 60 to control the driving of a cleaning device 80 that cleans the charge wire 88 of the charger 3.

Next, the control procedure of another embodiment of the present invention configured as described above will be explained using the flowcharts shown in FIGS. 12 to 14. In FIG. 12, steps 31 to S7
The operations up to this point are similar to those of the above embodiment, and in this embodiment, image unevenness is detected every 500 sheets. That is, step S7
If it is determined that the number of sheets has exceeded 500, the process proceeds to the image unevenness detection routine of step S40 shown in FIG. In this routine, the routine first proceeds to the transfer unevenness detection routine shown in FIG. 14 (step 541), where it is determined whether or not there is transfer unevenness (step 542). If there is no transfer unevenness, that is, if there is no image unevenness, the process proceeds to step S50. Reset the variable P to 0 and return to the main routine. If there is uneven transfer,
The process advances to a routine for detecting density unevenness by the image density sensor 7.

This routine is similar to that shown in FIG.

Next, step 544 determines whether or not there is density unevenness.
), if there is no density unevenness, it is determined that the cause of the image unevenness is an abnormality in the transfer charger 6, and “C” is displayed on the abnormality display section 111.
3" is displayed, and the serviceman call display section 11
2 is lit to prohibit copying operations (step 547).

If it is determined in step S44 that there is density unevenness, the process advances to step S45, a charging unevenness detection routine.

This routine is similar to that shown in FIG.

Next, it is determined whether there is charging unevenness (step 546), and if there is charging unevenness, it is determined that the cause of the image unevenness is an abnormality in the charging charger 3, and "C1" is displayed on the abnormality display section 111 (step 348). . If there is no charging unevenness, it is determined that the cause of the image unevenness is an abnormality in the developing device 5, and "C2" is displayed on the abnormality display section 111, the serviceman call display section 112 is lit, and copying operations are prohibited. .

After the display, the variable P is reset to 0 and the process returns to the main routine.

Note that when the serviceman call display section 112 lights up, the copying operation is prohibited until a reset switch (not shown) is operated.

As shown in FIG. 14, the transfer unevenness detection routine in step S41 first turns on the charging charger 3 and the exposure lamp 21, and drives the photosensitive drum 1, developing unit 5, and conveyance system (step 551). At this time, the scanner 24 is at the home position outside the document scanning area, and the document glass 10 is
The reference pattern 12 is located directly below the reference pattern 12 provided on the home position side. The amount of light from the exposure lamp 21 is set at a predetermined level at which a halftone image is formed on the photoreceptor drum 1.

At this point, a timer (not shown) is turned on (step 552), which is 1. When Osec is counted, the charger 3 and the exposure lamp 21 are turned off, the photosensitive drum 1, the developing device 5, and the conveyance system are stopped, and the timer is reset (steps S53 and 554). This 1.0 SEC is the point X on the photosensitive drum 1 shown in FIG. 1 in this copying machine.
, the charged area reaches the exposure point X2, the development area X4, and the transfer area It's time.

As a result, the copy paper on which the halftone toner image is formed is conveyed and stopped in the detection area X7 of the image density sensor 15, and the image density sensor 5 is moved over the toner image to detect the image density. Step 555). The change in detection voltage here is similar to that shown in FIG.

In other words, if the halftone image is uniform, the output voltage will be constant, but as shown in Figure 9, if there is a dark area in some areas, the output voltage will be lower than the reference voltage VL, and if it is thin, the output voltage will be higher than the base Y$ lightning voltage H. (In other words, the output voltage is the reference voltage VH ~ V
If it is within the range of L, there is no output from the comparators 67 and 68 and it is stored as no density unevenness. Further, if it is outside the range, since there is an output from the comparators 67 and 68, this output is stored as density unevenness (step 356).

Next, when the image density sensor 15 moves to the edge of the copy paper and turns on the switch 57 or 158, the movement of the image density sensor 15 is stopped (steps S57, 558).

Next, the conveyor 32 is driven (step 559), the timer is turned on (step 560), and this is 3.0 se.
Step 562) Stop the transport system when the time has elapsed.
, eject the copy paper from the copier. This 3. Osec is the time required for the copy paper to pass through the fixing device 30 and be discharged after detection. This post-processing returns to the image unevenness detection routine. Therefore, the difference between this transfer unevenness detection routine and the density unevenness detection routine described above is that in this routine, after copy paper is fed and an image (halftone image) is transferred to the copy paper, the paper is stopped, and after detection, The conveyance system is then driven again for a predetermined period of time to discharge it.

As explained above, in this embodiment, the test image (halftone image) on the copy paper, which is the final image, is checked, and if there is unevenness in density, the image on the photoreceptor drum is checked, and the charging check is performed at the stage before it becomes an image. Since the processing procedure narrows down the checking target from the final stage to the initial stage of the image forming process, if there is no abnormality, the image unevenness detection routine can be immediately terminated.1 This reduces the time required for abnormality checking. can be minimized.

In the above two examples, each abnormality was determined by comparing the surface potential and image density of the photoreceptor and the image density of the copy paper with the reference level. If the difference exceeds a predetermined level, it may be determined that there is uneven charging or uneven density. In this way, it is possible to detect only the unevenness of the surface potential and image density, regardless of a decrease in the overall level.

Further, in the above two embodiments, detection is performed while moving the image density sensor 7 and the surface potential sensor 4 along the photoreceptor, but if each sensor is arranged in an array over the detection range,
No mechanical driving means is required, and detection can be performed in a short time.

Furthermore, in the above two embodiments, a halftone toner image was formed on the photoreceptor drum and/or copy paper to detect density unevenness, but no exposure was performed at all to form a toner image for measurement. It may also be formed.

〔effect〕

As described above, in the image forming apparatus according to the present invention, the surface potential of the charged photoreceptor is detected by the sensor, and a toner image is developed and formed on the photoreceptor and/or paper with a predetermined exposure amount. Each image density sensor is configured to detect density unevenness, and as a result, charging unevenness is not detected by the surface potential sensor, and only density unevenness on the photoconductor or density unevenness on the paper is detected. If this occurs, it is determined that the problem is not due to dirt or the like on the charger, but rather to an abnormality in the developing device or transfer charger, so repairs can be quickly carried out, and damage can be minimized. Furthermore, if the charger is dirty, cleaning the wire can immediately eliminate image unevenness, providing excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration when an image forming apparatus according to the present invention is applied to a copying machine, and a block diagram of a control system;
Fig. 2 is a plan view showing the configuration of the operation panel, Fig. 3 is a device block diagram of the surface potential sensor and image density sensor, Fig. 4 is a block diagram of the charge wire cleaning device, and Fig. 5 is the main routine of the control system. 6 is a flowchart showing the density unevenness detection procedure, FIG. 7 is a flowchart showing the charging unevenness detection procedure, FIG. 8 is a flowchart showing the abnormality processing procedure, and FIG. 9 is a flowchart showing the image density detection procedure. FIG. 10 is a graph showing an example of a change in voltage; FIG. 10 is a graph showing an example of a change in surface potential detection voltage; FIG. 12 is a flowchart showing the main routine processing procedure of another embodiment, FIG. 13 is a flowchart showing the unevenness processing procedure, and FIG. 14 is a flowchart showing the transfer unevenness detection procedure. 3... Charger 4... Surface potential sensor 5
...Developer 6...Transfer charger 7...Image density sensor 15...Image density sensor 88...Charge wire 60...CPU 61.62, 63,
64,67.68...Comparator 80...Cleaning device

Claims (1)

[Claims] 1. A developing device that develops with toner an electrostatic latent image formed by exposure on a photoconductor charged with an electrostatic charger, and detecting the surface potential of the charged photoconductor. An image forming apparatus comprising: a latent image forming means for forming an electrostatic latent image with a predetermined exposure amount on the photoconductor; and a latent image forming means for forming an electrostatic latent image formed by the latent image forming means A density sensor that detects the density of the toner image developed by the developing device; and means for determining whether the operating state of the charger and the developing device is good or bad based on the detection results of the surface potential sensor and the density sensor. An image forming apparatus characterized by: 2. A transfer charger that transfers the developed toner image to a transfer body; A transfer density sensor that detects the density of the toner image transferred by the transfer charger; and each of the surface potential sensor, density sensor, and transfer density sensor. 2. The image forming apparatus according to claim 1, further comprising means for determining whether the operating states of the charging charger, the developing device, and the transfer charger are good or bad based on the detection results.