JP2010048960A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control voltage output to a developing device considering influence on image formation by a change in the atmospheric pressure, without having to provide an air pressure sensor in an electrophotographic image forming apparatus. <P>SOLUTION: The image forming apparatus includes: a charge device which charges a photoreceptor; an exposure device which exposes the charged photoreceptor to form a latent image; the developing device which develops an image, by making the toner adhere to the photoreceptor; a transfer device which transfers the toner adhered to the photoreceptor to paper; and a fixing device which fixes the toner transferred to the paper. The image forming apparatus includes an applying means for applying a high voltage as a power supply for each device; a detection means to detect a leakage current caused when applying the high voltage; and a control means to control the high voltage to be applied to the developing device, according to the leakage current detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In recent years, in an image forming apparatus, various controls are performed on an image forming process in order to obtain a high-quality image even when the external environment of the installation location changes.

  For example, a copying machine that uses a corona discharger as a charging device or a copying machine that applies a high voltage to a gap between a developing sleeve and a photosensitive member as a developing device, such as an external environment such as temperature or The quality of the final image is relatively greatly affected by humidity and the like.

  Therefore, image forming conditions of an image forming process such as a developing device are appropriately changed according to the environment.

  Especially in high altitude areas, the atmospheric pressure is low, and proper charging and development cannot be performed when a high voltage is applied to the gap between the photoconductor and the corona discharger, or the gap between the photoconductor and the developing device. , The image quality is significantly reduced.

  Therefore, a technique for obtaining a stable and high-quality image regardless of environmental changes has been proposed (see, for example, Patent Documents 1 and 2).

  In the invention described in Patent Document 1, an atmospheric pressure detection sensor is provided, and the control device appropriately changes the image forming conditions of the developing device or the like according to the output. Specifically, the gap potential difference is adjusted based on the output of the atmospheric pressure detection sensor so that the gap potential difference does not exceed the leak limit potential difference.

The invention described in Patent Document 2 relates to a developing device, and when a pressure sensor detects that the altitude exceeds 2000 m, the switching controller can change the value of the developing bias Vmax to a low value. I have to.
JP 05-088434 A Japanese Patent Laid-Open No. 07-134480

  However, in the inventions described in Patent Documents 1 and 2, an atmospheric pressure sensor is required to detect atmospheric pressure and control the voltage applied to the developing device based on the detection result.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an effect of changes in atmospheric pressure on image formation without providing a barometric pressure sensor in an electrophotographic image forming apparatus. Is to provide an image forming apparatus capable of controlling the voltage output to the developing device.

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

  (1) A charging device that charges the photosensitive member, an exposure device that exposes the charged photosensitive member to form a latent image, a developing device that attaches toner to the photosensitive member and develops, and a toner that adheres to the photosensitive member An image forming apparatus having a transfer device for transferring the toner onto a sheet and a fixing device for fixing the toner transferred onto the sheet, and applying means for applying a high voltage as a power source of each device, and applying the high voltage An image forming apparatus comprising: a detecting unit that detects a leakage current that occurs when the image is generated; and a control unit that controls the high voltage applied to the developing device in accordance with the detected leakage current.

  (2) The image forming apparatus according to (1), further including a switching unit that switches ON / OFF operation of the detection unit by interrupting a leak current generated when the high voltage is applied.

  (3) The image forming apparatus according to (1), wherein the leakage current is detected by current-voltage conversion.

  (4) The transfer device includes a primary transfer unit that transfers the toner adhered on the photosensitive member to the intermediate member, and a secondary transfer unit that transfers the toner transferred to the intermediate member to a sheet, and the detection unit. The image forming apparatus according to (1), wherein a leak current generated when a high voltage is applied to the primary transfer unit is detected.

  (5) The image forming apparatus according to (1), wherein the detection unit detects a leak current generated when a high voltage is applied to a scorotron charger.

  (6) The image forming apparatus according to (1), wherein the detection unit detects a leak current generated when a high voltage is applied to a roller charging type charger.

  (7) The transfer device includes a primary transfer unit that transfers the toner adhered on the photosensitive member to the intermediate body, and a secondary transfer unit that transfers the toner transferred to the intermediate body to a sheet, and the detection unit. The image forming apparatus according to (1), wherein a leak current generated when a high voltage is applied to the secondary transfer unit is detected.

  (8) The image forming apparatus according to (1), wherein the detection unit detects a leak current generated when a high voltage is applied to the developing device.

  In the present invention, in the electrophotographic image forming apparatus, the voltage output to the developing device can be controlled in consideration of the influence of changes in atmospheric pressure on image formation without providing a pressure sensor.

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

  FIG. 1 is a configuration diagram schematically showing the overall configuration of the printer according to the present embodiment. The printer according to this embodiment is a tandem type color laser printer, and has a mechanism in which process units are connected to four color tandems for each color, and after each color is sequentially transferred as a toner image onto a transfer belt as an intermediate. The toner images for four colors are transferred onto the paper at once.

  The printer forms a toner image on the surface of the image carrier 11, 16, 21, 26 by feeding the paper in the paper cassette 1 by the paper feed roller 2, and rotates the transfer belt 8 to sequentially transfer the toner. 8 includes process units Y, M, C, and K that are primarily transferred to 8, a secondary transfer unit that transfers the toner image on the transfer belt 8 to a sheet, and a fixing unit that fixes the toner image transferred to the sheet. Composed.

  The paper feed unit has a paper feed cassette 1, a paper feed roller 2, and a timing roller 4, and sends out the paper in the paper feed cassette 1 to the secondary transfer position.

  Sheets for recording images are stored in the sheet feeding cassette 1, and the sheets in the sheet feeding cassette 1 are fed out one by one by a sheet feeding roller 2. The paper fed out by the paper feed roller 2 is sent out to the secondary transfer position along the paper feed path 3 by the timing roller 4.

  The process units Y, M, C, and K include image carriers 11, 16, 21, and 26, chargers 14, 19, 24, and 29, exposure units 13, 18, 23, and 28, and development units 12 and 17, respectively. , 21 and 27 and primary transfer rollers 10, 15, 20, and 25, and each color toner image is formed on a transfer belt 8 as an intermediate.

  Each process unit uses toner of each color, where the process unit Y is yellow (Y), the process unit M is magenta (M), the process unit C is cyan (C), and the process unit K is black (K). In the following description, the process unit Y for developing yellow (Y) toner will be mainly described, but the same applies to other process units.

  The chargers 14, 19, 24, and 29 uniformly charge the surfaces of the image carriers 11, 16, 21, and 26 as rotating drum type image carriers. As charging methods, there are a contact type roller charging method and a non-contact type corona charging method.

  In the roller charging method, a photosensitive roller is charged by contacting a charging roller. There are two types of roller charging methods: an AC voltage application method and a DC voltage application method. Generally, a DC voltage or a vibration voltage (bias voltage) obtained by superimposing an AC voltage on a DC voltage is applied to the charging roller. By doing so, the image carrier is charged.

  In the corona charging method, ions generated by corona discharge are guided to the surface of the image carrier to be charged.

  The corona charging method includes a scorotron charger having a grid electrode disposed in a mesh shape between a corona wire in which a tungsten wire is shielded with a metal and an image carrier, and a corotron charger having no grid electrode. In the scorotron charger, a grid electrode is attached to the opening surface of the corona discharger, and a bias voltage is applied to the grid electrode, whereby the charged potential on the surface of the image carrier is uniformly controlled.

  In the present invention, any charging method is applicable.

  The exposure devices 13, 18, 23, and 28 irradiate laser light modulated in accordance with the image signal, scan and expose the surfaces of the image carriers 11, 16, 21, and 26, and then the electric latent image ( Electrostatic latent images) are formed on the image carriers 11, 16, 21, 26. Due to this scanning exposure, the potential irradiated with the laser light on the surfaces of the image carriers 11, 16, 21, 26 decreases, and the image carriers 11, 16, 21, 26 correspond to the image information scanned and exposed. A charge pattern (electrostatic latent image) is formed.

  Developers 12, 17, 21, and 27 cause toner to adhere to the image carriers 11, 16, 21, and 26 on which the electrostatic latent image is formed by electrostatic force. Therefore, the latent image is visualized with toner.

  Dry development methods include a one-component development method and a two-component development method. In the two-component development method, a developer in which a nonmagnetic toner and a carrier for imparting electric charge to the toner are mixed is used, and the toner and the carrier are stirred and rubbed to give an appropriate charge amount to the toner. In the one-component development method, a magnetic toner provided with an appropriate charge amount is used as a developer.

  The developer is formed as a thin layer on the surface of the developing roller, and a bias voltage is applied to the developing roller, so that the toner in the developer flies and static images formed on the surfaces of the image carriers 11, 16, 21, and 26 are formed. It adheres corresponding to the electrostatic latent image. Therefore, the latent image is visualized as a toner image.

  Here, in general, the printer applies a high voltage (1500 v) to the developing roller to form an electrostatic latent image on the surface of the carrier. Therefore, when a higher voltage (2000 v) is applied to the developing roller, a discharge occurs between the developing roller and the carrier, resulting in an image abnormality. On the other hand, when a low high voltage (500 v) is applied to the developing roller, the toner does not sufficiently fly from the developing roller to the carrier, resulting in an image abnormality. Accordingly, if the voltage applied to the developing roller is too high or too low, an image abnormality is caused. Therefore, an appropriate voltage value must be applied to the developing roller.

  The transfer belt 8 is endless, suspended from the opposing roller 6 and the transfer belt drive roller 9 and rotated counterclockwise in the figure. Primary transfer rollers 10, 15, 20, 25 are arranged on the opposite side of the image carrier 11, 16, 21, 26 across the transfer belt 8, and press the transfer belt 8 in pressure contact therewith.

  The transfer belt 8 is first fed into the yellow process unit Y, and a high voltage is applied to the primary transfer roller 10 on the back side of the transfer belt 8 so that the yellow image formed on the image carrier 11 is transferred to the transfer belt 8. 8 is transferred. Next, the transfer belt 8 passes through the process units M, C, and K of the respective colors, and the toner images of the respective colors of magenta, cyan, and black are sequentially placed on the transfer belt 8 through the same processes as described above.

  The secondary transfer unit has a counter roller 6 on which the transfer belt 8 is suspended and a secondary transfer roller 5 disposed at a position opposite to the counter roller 6, and transfers the toner image on the transfer belt 8 to a sheet. Let

  The timing sensor 30 feeds the paper at the same timing so that the leading edge of the paper coincides with the leading edge of each color toner image transferred to the transfer belt 8. By applying a high voltage to the secondary transfer roller 5 in close contact with the paper, the toner image charged on the transfer belt 8 is transferred to the paper by electrostatic force.

  The fixing unit has a pair of fixing rollers 7 and fuses the toner image adhering to the paper by applying pressure and heating. The paper on which the toner image is placed is sandwiched between the fixing roller (heat roller) on the side in contact with the toner image and the pressure roller on the backup side, and passes through the nip where the fixing roller contacts, so that heat and pressure are applied to the paper. And the toner is fused to the paper.

  In addition, the printer is provided with a toner density detection sensor 31 to keep the toner density in printing constant. Specifically, image stabilization control is performed to keep the printing density constant, such as when the main switch of the printer body is turned on, when the toner cartridge is replaced, or when a predetermined number of sheets are printed.

  In the image stabilization control, the toner density is stabilized by forming a toner patch (reference toner image) on the transfer belt 8 and feeding back the detection result of the detected toner density by changing the development output to the development output. Is intended.

  Specifically, several toner patches (about 10 mm square) for toner density detection are formed on the transfer belt 8. The development output of the developing device is changed, and the density of the toner patch printed with a different toner density is detected by the toner density detection sensor 31. The development output of the developing device is controlled according to the detection result, and the toner density during printing is kept constant. Note that image stabilization control is performed for each color in the case of a color printer.

  Next, printer processing during printing will be described.

  When a print start request is transmitted from an image controller (not shown) to the printer, a printing operation is started. The printer feeds paper from the paper feed cassette 1 by the paper feed roller 2, feeds the paper along the paper feed path 3, and waits for the paper at the position where it reaches the timing sensor 30.

  The printer rotates a transfer belt 8 that is an image carrier by a transfer belt driving roller 9. The printer forms a toner image on the transfer belt 8 by each process unit that forms an image of each color.

  Specifically, in each process unit, the developing roller driving motor is started, the developing roller rotates, and a developing voltage is applied to the developing roller, whereby the toner on the developing roller is transferred to the image carrier 11, Developed on 16, 21, 26. The toner images developed on the color image carriers 11, 16, 21, 26 are transferred onto the transfer belt 8 by the primary transfer rollers 10, 15, 20, 25.

  The printer drives the timing roller 4 in accordance with the timing at which the position of the image formed on the transfer belt 8 reaches the position of the secondary transfer roller 5, thereby matching the front end position of the sheet with the image position. . The printer applies a transfer voltage to the secondary transfer roller 5 to transfer the toner forming an image on the transfer belt 8 onto a sheet passing between the opposing roller 6 and the secondary transfer roller 5. .

  The toner image transferred onto the paper is fixed on the paper by the fixing roller 7 and discharged onto a paper discharge tray at the top of the printer.

  FIG. 2 is a configuration diagram showing the configuration of the printer, focusing on the circuit configuration of the primary transfer high-voltage power supply.

  The high-voltage power supply includes a primary transfer high-voltage power supply 107, a secondary transfer high-voltage power supply 108, a charging high-voltage power supply 109, and a development high-voltage power supply 110, and an output voltage is controlled by the CPU 101. Hereinafter, the process unit K for developing the black (K) toner will be mainly described, but the same applies to the other process units.

  The primary transfer high-voltage power supply 107 applies an output voltage (about 2000 V) from the output terminal A to the primary transfer roller 25 in accordance with a signal from the DA port 102 of the CPU 101 in the control board 100, and carries an image in the process unit. The toner image is transferred from the body 26 to the primary transfer belt 8.

  In response to a signal from the DA port 106 of the CPU 101, the secondary transfer high-voltage power supply 108 applies an output voltage (about 2000 V) from the output terminal D to the counter roller 5, and the toner image is transferred from the transfer belt 8 to the sheet. Control.

  The charging high-voltage power supply 109 applies an output voltage (about 5000 v) from the output terminal C to the charger 29 in accordance with a signal from the DA port 105 of the CPU 101, and the image carrier 29 is charged in the process unit K. To control.

  The developing high-voltage power supply 110 applies an output voltage (about 1500 v) from the output terminal B to the developing device 27 in response to a signal from the DA port 104 of the CPU 101, and the image carrier 26 is developed with toner in the process unit K. To be controlled.

  A circuit configuration for leak detection of the primary transfer high-voltage power supply 107 will be described.

  The CPU 101 in the control board 100 outputs a voltage value as a signal from the DA port 102 to the transformer drive control circuit 107f. The transformer drive control circuit 107 f controls the excitation current of the primary transfer transformer 107 a according to the voltage value from the DA port 102. An electromotive force corresponding to the exciting current is generated in the secondary winding of the primary transfer transformer 107a. The generated voltage is half-wave rectified by the rectifier diode 107c and the capacitor 107d, and is output from the output terminal A through the high-voltage output line 107k.

  The voltage output from the output terminal A is input to the transformer drive circuit 107f via the feedback line 107j. The transformer drive circuit 107f controls the voltage value output from the output terminal A to be constant based on the voltage input from the feedback line 107j.

  The output terminal A is connected to the primary transfer roller 25 via a high-voltage cable, and an output voltage is applied to the primary transfer roller 25 to control the transfer of the toner image from the image carrier 26 to the primary transfer belt 8.

  Further, the CPU 101 reads a voltage value corresponding to the leak current 107 i from the AD port 103 and stores it in the memory 116. The leak current 107i is a current generated when a high voltage is output to the output terminal A, is detected using the leak detection pattern 107g, and is converted into a voltage by the resistor 107h.

  Further, a temperature / humidity sensor 114 is connected to the CPU 101, and the CPU 101 reads a voltage value corresponding to humidity from the AD port 112 and reads a voltage value corresponding to temperature from the AD port 117.

  As described above, the voltage value corresponding to the current generated when the high voltage is output is detected by using the leak detection pattern 107g, and the high voltage applied to the developing device is controlled, so that the atmospheric pressure sensor is not provided. The voltage (development bias) output to the developing device can be controlled in consideration of the effect of changes in atmospheric pressure on image formation. By doing so, the printer can appropriately correct the developing bias according to the environment and obtain a stable high-quality image. The leak detection pattern can be added to the existing circuit configuration, and the present invention can also be applied to an existing printer.

  The principle of the present invention will be described with reference to FIGS.

  FIG. 3 is a diagram illustrating a leak detection pattern and a high-voltage output line in the embodiment. FIG. 4 is a diagram showing the relationship between leakage current and atmospheric pressure. FIG. 5 is a diagram showing the relationship between the leakage current and the development bias correction value.

  A leak detection pattern 107g having a width of 0.5 mm and a high-voltage output line 107k were formed on a paper phenol substrate at a distance of 1 mm on the same axis. A voltage (1800 v) was applied to the high-voltage output line 107k while changing the atmospheric pressure.

  As a result, as shown in FIG. 4, it can be seen that the leakage current 107 i increases at high altitude (760 hPa) compared to flat ground (1008 hPa). That is, it can be seen that the leakage current 107i also changes as the atmospheric pressure changes.

  In the present invention, the relationship between the leak current and the developing bias correction value shown in FIG. 5 is calculated and stored in the memory 116 in advance. The printer can set the optimum developing bias by detecting the leakage current 107i at the time of startup and calculating the correction value using the relationship between the leakage current and the correction value of the developing bias. In other words, by using the relationship between the leakage current and the correction value of the development bias, the correction of the development bias can be calculated linearly instead of stepwise, and an optimal development bias can be set.

  Next, a modification of the present embodiment will be described with reference to FIG.

  FIG. 6 is a block diagram showing a modification of the printer shown in FIG. Note that, among the respective units of the printer, the description of the portions having the same functions as those of the respective units shown in FIG.

  In the configuration shown in FIG. 2, when the primary transfer output is used as a constant current, there is a possibility that an error may occur in the constant current due to a leakage current. In this case, it is necessary to cut off the leak current 107i flowing through the leak detection pattern 107g.

  In the modification shown in FIG. 6, the transistor 120 blocks the leakage current 107i to the leakage detection pattern 107g.

  The transistor 120 is inserted into the leak current line, and the base current of the transistor 120 is controlled via the resistor 118. That is, by turning ON / OFF the current at the base of the transistor 120, the current between the collector and the emitter is also turned ON / OFF, the leakage current 107i flows or is cut off in the leakage current line, and the leakage detection pattern 107g is ON / OFF control is performed.

  By doing so, it is possible to suppress an error due to a leakage current when the primary transfer output is used as a constant current.

  The ON / OFF control of the leak detection pattern is not limited to the case where the transistor switching action is used, but can also be performed by a relay switch using an electromagnet.

  In addition, when using the primary transfer output with a constant current, the error due to the leakage current is measured in advance, and the constant current is output by overlapping the currents measured when the constant current is output. May be.

  In the above embodiment, the transformer drive control circuit 107f controls the excitation current using the single-output type primary transfer transformer 107a. However, the present invention can also be applied to a two-output type transformer.

  FIG. 7 is a circuit diagram schematically showing a circuit configuration when a two-output type transformer is used. The exciting current of the primary transfer transformer 107a is controlled. An electromotive force corresponding to the exciting current is generated in the secondary winding of the primary transfer transformer 107a.

  The first output voltage generated in the secondary winding is half-wave rectified by the rectifier diode 107c and the capacitor 107d, and is directly output from the output terminal A via the high-voltage output line 107k.

  Since the second output voltage generated in the secondary winding outputs the same voltage value as that of the output terminal A, the leak current generated at this time is detected using the leak detection pattern 107g and is detected by the resistor 107h. The voltage is converted and output to the AD port 103 of the CPU.

  By doing so, even if the primary transfer output is used as a constant current, an error does not occur in the constant current due to the leakage current.

  FIG. 8 is a flowchart showing a process for determining the developing bias.

  The voltage output for leak detection is turned on (step S1).

  The CPU 101 outputs an analog voltage from the DA port 102 and outputs a predetermined high voltage from the high voltage power source 107.

  A leak current value is detected (step S2). The CPU 101 measures the leak current from the AD port 103.

  A correction value for the output voltage is determined (step S3). The CPU 101 determines a correction value for the developing bias based on the detected leakage current value.

  A development bias is determined (step S4). The CPU 101 determines the development bias based on the calculated correction value.

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

  In the above-described embodiment, the leak detection circuit is provided in the primary transfer high-voltage power supply, but the present invention is not limited to this. The present invention corrects fluctuations due to changes in atmospheric pressure by detecting a leakage current generated when a high-voltage power supply is applied. It can also be applied to power supplies.

  In the above embodiment, the tandem color laser printer has been described as the image forming apparatus of the present invention, but the present invention is not limited to this. In the above embodiment, the tandem method is adopted as the transfer method, but the present invention can also be applied to a four-cycle method, and the light source is not limited to the laser light source, and a light emitting diode may be used. The present invention is also applicable to an image forming apparatus using an electrophotographic system such as an MFP (Multi-Function Peripheral), a digital copying machine, a facsimile, or the like.

1 is a configuration diagram schematically illustrating an overall configuration of a printer according to an embodiment. FIG. 2 is a configuration diagram illustrating a configuration of a printer with a focus on a circuit configuration of a primary transfer high-voltage power supply. It is a figure which shows the pattern for a leak detection, and a high voltage | pressure output line. It is a figure which shows the relationship between leak current and atmospheric pressure. It is a figure which shows the relationship between the leak current and the correction value of the developing bias. It is a flowchart which shows the procedure of the process which determines a bias voltage. It is a circuit diagram which shows typically the circuit structure at the time of using a 2 output type transformer. It is a flowchart which shows the process in which development bias is determined.

Explanation of symbols

1 paper cassette,
2 paper feed rollers,
3 Paper feed path,
4 Timing roller,
5 Secondary transfer roller,
6 Opposing roller,
7 Fixing roller,
8 Transfer belt,
9 Transfer belt drive roller,
10 Y color primary transfer roller,
11 Image carrier for Y color,
12 Y toner developer,
13 Y toner exposure unit,
14 Y-color toner charger,
15 M color primary transfer roller,
16 M color image carrier,
17 M toner developer,
18 M toner exposure unit,
19 M color toner charger,
20 C primary transfer roller,
21 C color toner developer,
22 C color image carrier,
23 C color toner exposure device,
24 C color toner charger,
25 K color primary transfer roller,
26 K color image carrier,
27 K color toner developer,
28K color toner exposure device,
29K toner charger,
30 Timing sensor,
31 toner density detection sensor,
Development motor for developing 33 K color toner,
Development motor for 34 C color toner development,
Development motor for 35 M toner development,
36 Development motor for Y toner development,
100 control board,
101 CPU,
102 D / A output port,
103 A / D input port,
104 D / A output port,
105 D / A output port,
106 D / A output port,
107 High-voltage power supply for primary transfer,
108 High-voltage power supply for secondary transfer,
109 high-voltage power supply for charging,
110 High-voltage power supply for development,
112 A / D input port,
114 temperature and humidity sensor,
116 memory,
117 A / D input port,
119 A / D input port,
120 transistor.

Claims (8)

A charging device that charges the photosensitive member, an exposure device that exposes the charged photosensitive member to form a latent image, a developing device that attaches toner to the photosensitive member and develops the toner, and the toner attached on the photosensitive member to the paper An image forming apparatus having a transfer device for transferring, and a fixing device for fixing toner transferred to a sheet,
Applying means for applying a high voltage as a power source of each device;
Detecting means for detecting a leakage current generated when the high voltage is applied;
Control means for controlling the high voltage applied to the developing device according to the detected leakage current;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising a switching unit that switches an ON / OFF operation of the detection unit by interrupting a leak current generated when the high voltage is applied.   The image forming apparatus according to claim 1, wherein the leak current is detected by current-voltage conversion. The transfer device includes a primary transfer unit that transfers the toner adhered on the photoreceptor to the intermediate body, and a secondary transfer unit that transfers the toner transferred to the intermediate body to a sheet,
The image forming apparatus according to claim 1, wherein the detection unit detects a leak current generated when a high voltage is applied to the primary transfer unit.   The image forming apparatus according to claim 1, wherein the detection unit detects a leakage current generated when a high voltage is applied to a scorotron charger.   The image forming apparatus according to claim 1, wherein the detection unit detects a leak current generated when a high voltage is applied to a roller charging type charger. The transfer device includes a primary transfer unit that transfers the toner adhered on the photoreceptor to the intermediate body, and a secondary transfer unit that transfers the toner transferred to the intermediate body to a sheet,
The image forming apparatus according to claim 1, wherein the detection unit detects a leak current generated when a high voltage is applied to the secondary transfer unit.   The image forming apparatus according to claim 1, wherein the detection unit detects a leak current generated when a high voltage is applied to the developing device.

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