JP7704028B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus, and is suitable for use in, for example, electrophotographic image forming apparatuses.

Conventionally, image forming devices (also called printers) have been widely used in which a toner image is formed by an image forming unit using toner (also called developer) based on an image supplied from a computer device or the like, the toner image is transferred to a medium such as paper, and the image is then fixed by applying heat and pressure in a fixing device, thereby carrying out a printing process. One such image forming device is one that detects blown fuses in high-voltage circuits and faults in high-voltage transformer circuits (see, for example, Patent Document 1).

JP 2016-38491 A

In such image forming devices, it is desirable to improve convenience while maintaining reliability.

The present invention was made in consideration of the above points, and aims to propose an image forming device that can improve convenience while maintaining reliability.

In order to solve this problem, the image forming device of the present invention is provided with multiple high-voltage circuits that are supplied with driving voltage from the same voltage source and output to their respective external loads, and a control unit that detects the output state of each of the multiple high-voltage circuits to the external load; if the control unit detects an abnormality in only one of the outputs of the multiple high-voltage circuits during printing operation, it stops the transport of the medium being printed before ejection is complete, but if it detects an abnormality in the outputs of all of the multiple high-voltage circuits during printing operation, it ejects the medium from the device.

If an abnormality is detected in only one of multiple outputs during a printing operation, the present invention can prevent abnormalities in the transport of the medium being printed and discharge by stopping the transport of the medium before ejection is complete, and if an abnormality is detected in all of the multiple outputs during a printing operation, the medium in the image forming device is ejected, preventing media from remaining in the image forming device and causing a jam.

The present invention makes it possible to realize an image forming device that can improve convenience while maintaining reliability.

FIG. 2 is a left side view showing the internal configuration of the printer. FIG. 2 is a block diagram showing a configuration of a printer control unit. FIG. 2 is a block diagram showing a configuration of a high-voltage circuit. 11 is a flowchart showing a high-voltage circuit abnormality detection process procedure (1). 13 is a flowchart showing a high-voltage circuit abnormality detection process procedure (2).

Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[1. Configuration of image forming apparatus]
1, the printer 1 is a monochrome electrophotographic printer that performs monochrome printing and prints a desired monochrome image on a print medium P, which is paper of a size such as A3 or A4. The printer 1 is controlled by a printer control unit 40. When the printer control unit 40 receives print data from an external device via an interface (not shown) such as a Universal Serial Bus (USB) or a Local Area Network (LAN), the printer control unit 40 starts printing by controlling each unit of the printer 1.

A display operation unit 3 is provided on the front upper surface outside the device housing 2. The display operation unit 3 is composed of a combination of a specified display panel and specified operation buttons. The display panel of the display operation unit 3 displays the operating status of the printer 1, for example, indicating that an abnormality has been detected and the location of the abnormality. The operation buttons of the display operation unit 3 receive instructions, for example related to printing, when pressed by the operator.

Inside the device housing 2, various parts are arranged along the transport path 6 along which the print medium P is transported. A paper feed cassette 4 that stores the print medium P is provided at the bottom inside the device housing 2. A pair of hopping rollers 8 that pay out the print medium P from the paper feed cassette 4 to the transport path 6 is provided at the front upper side of the paper feed cassette 4. A pair of registration rollers 9 and 10 are provided downstream of the hopping rollers 8 in the transport direction of the print medium P on the transport path 6 that correct any skew of the print medium P paid out by the hopping rollers 8 and send it to the image forming unit 12 at a predetermined timing.

Inside the device housing 2, near the upper front side, there is provided one image forming unit 12 that corresponds to the color of developer (e.g., black (K) toner) used by the printer 1.

The image forming unit 12 forms an electrostatic latent image on the surface of the photosensitive drum 34 by irradiating the surface of the photosensitive drum 34 with light using an LED (Light Emitting Diode) head 16, and then forms a toner image on the surface of the photosensitive drum 34 by attaching toner supplied from the toner cartridge 14 to the electrostatic latent image.

Furthermore, below the image forming unit 12 inside the device housing 2, a transfer roller 18 is provided, disposed opposite to and below the photosensitive drum 34. A positive high voltage transfer bias voltage is applied to the transfer roller 18 from the transfer bias circuit 70 (Figure 3), and the transfer roller 18 charges the print medium P with a polarity opposite to that of the toner when the print medium P passes between the photosensitive drum 34 and the transfer roller 18. This causes the transfer roller 18 to transfer the toner image formed on the photosensitive drum 34 to the print medium P.

Furthermore, inside the device housing 2, a fixing device 20 is provided downstream in the transport direction (i.e., rearward) of the image forming unit 12. The fixing device 20 has a fixing roller 21 having a halogen heater disposed above the transport path 6, and a backup roller 22 disposed below the fixing roller 21 and facing it with the transport path 6 in between. This fixing device 20 heats the fixing roller 21 to a fixing temperature by power input to the halogen heater, and fixes the toner image transferred to the print medium P by the transfer roller 18 onto the print medium P by heating and pressurizing it with the fixing roller 21 and backup roller 22.

Furthermore, a pair of discharge rollers 24 that transport the print medium P to the paper discharge port 2B is provided on the transport path 6 between the fixing unit 20 and the paper discharge port 2B inside the device housing 2. Further, a pair of discharge rollers 25 that discharge the paper from the paper discharge port 2B to the paper stacker unit 2A that accumulates the print medium P is provided downstream of the discharge rollers 24 on the transport path 6 in the transport direction.

2. Configuration of Image Forming Unit
The image forming unit 12 is made up of an ID unit 13 and a toner cartridge 14. The toner cartridge 14 stores toner as a developer therein, and is configured to be detachable from the ID unit 13.

The ID unit 13 incorporates a toner supply roller 30, a developing roller 32, a photosensitive drum 34, and a charging roller 36. The toner supply roller 30, the developing roller 32, the photosensitive drum 34, and the charging roller 36 are each configured in a cylindrical shape with their central axes aligned in the left-right direction.

The toner supply roller 30 supplies toner to the developing roller 32 by applying a supply bias voltage, which is a negative high voltage, from the supply bias circuit 68 (Figure 3). The developing roller 32 supplies toner to the photosensitive drum 34 by applying a development bias voltage, which is a negative high voltage, from the development bias circuit 66 (Figure 3).

The photosensitive drum 34 can be charged by sequentially forming a thin-film charge generating layer and a charge transport layer on the peripheral side. When the ID unit 13 is installed in the printer 1, it brings the underside of the photosensitive drum 34 into contact with the print medium P. The charging roller 36 charges the surface of the photosensitive drum 34 by applying a charging bias voltage, which is a negative high voltage, from the charging bias circuit 64 (Figure 3).

The LED head 16 is located above the photosensitive drum 34. This LED head 16 has multiple light-emitting element chips arranged in a straight line along the left-right direction, and each light-emitting element is made to emit light in an emission pattern based on image data signals supplied from the printer control unit 40.

In this configuration, the ID unit 13 receives driving force from the ID motor 44 (Figure 2) to rotate the toner supply roller 30, the developing roller 32, and the charging roller 36, and also rotates the photosensitive drum 34. Furthermore, the ID unit 13 applies a supply bias voltage, a developing bias voltage, and a charging bias voltage to the toner supply roller 30, the developing roller 32, and the charging roller 36, respectively.

The toner supply roller 30 is charged to cause toner to adhere to its peripheral surface, and rotates to cause the toner to adhere to the peripheral surface of the developing roller 32. The developing roller 32, with the toner adhered in a thin film form, abuts its peripheral surface against the peripheral surface of the photosensitive drum 34.

Meanwhile, the charging roller 36 contacts the photosensitive drum 34 in a charged state, uniformly charging the circumferential surface of the photosensitive drum 34. The LED head 16 sequentially exposes the charged photosensitive drum 34 by emitting light at predetermined time intervals in an emission pattern based on image data signals supplied from the printer control unit 40. As a result, electrostatic latent images for adhering a charged toner image are sequentially formed at exposed locations on the circumferential surface of the photosensitive drum 34 near its upper end.

The photosensitive drum 34 then rotates, bringing the area where the electrostatic latent image is formed into contact with the developing roller 32. This causes toner to adhere to the peripheral surface of the photosensitive drum 34 based on the electrostatic latent image, and a toner image based on the image data is developed. The photosensitive drum 34 then rotates further, causing the toner image to reach the vicinity of the bottom end of the photosensitive drum 34.

At this time, the printer 1 causes the print medium P to reach the bottom of the ID unit 13, and applies a transfer bias voltage to the transfer roller 18, thereby charging it with the opposite characteristics to the toner. As a result, the ID unit 13 clamps the print medium P between the part of the photosensitive drum 34 on which the toner image is formed and the charged transfer roller 18, and transfers the toner image to the print medium P.

[3. Configuration of the Printer Control Unit]
2, the printer control unit 40 has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (not shown), and performs various processes and print operations by executing predetermined programs read from the ROM etc. by the CPU. A paper feed motor 42, an ID motor 44, an LED head 16, a fixing motor 46, a fixing control unit 48, and a high voltage circuit 50 are connected to the printer control unit 40.

The feed motor 42 is a stepping motor that drives and rotates the hopping roller 8 and the registration rollers 9 and 10 to feed and transport the print medium P. The ID motor 44 is a brushless DC motor that drives and rotates the ID unit 13 and the transfer roller 18. The LED head 16 exposes the charged surface of the photosensitive drum 34. The fixing motor 46 is a brushless DC motor that drives and rotates the fixing roller 21 and the discharge rollers 24 and 25. The fixing control unit 48 controls the heating of the halogen heater of the fixing unit 20. The high voltage circuit 50 is a circuit that generates high voltages for the functions of charging, developing, and transferring that are possessed by the ID unit 13.

[4. High-voltage circuit configuration]
3, the high voltage circuit 50 is connected to a constant voltage source 54 and is supplied with a driving voltage of 24 V, and outputs a high voltage bias voltage to the charging roller 36, the developing roller 32, the toner supply roller 30, and the transfer roller 18. A fuse 62 is inserted between the constant voltage source 54 and the high voltage circuit 50. The fuse 62 is mounted on a board separate from the high voltage circuit 50, and melts down when the connection cord is shorted to ground, the external output terminal of the high voltage circuit 50 is shorted to ground, or the high voltage circuit 50 fails. When the fuse 62 melts down, the high voltage circuit 50 is unable to output any high voltage bias voltage, and the print result on the print medium P is blank.

The high voltage circuit 50 has a charging bias circuit 64, a developing bias circuit 66, a supply bias circuit 68, and a transfer bias circuit 70.

The charging bias circuit 64 outputs a charging bias voltage, which is a negative high voltage of about -1000 [V], to the charging roller 36, which is an external load, by inputting a voltage setting signal S1 from the printer control unit 40. The charging bias circuit 64 also inputs an output voltage signal S2 indicating the output voltage value of the charging bias voltage to the printer control unit 40. When the absolute value of the charging bias voltage becomes a voltage lower than a predetermined set value, the surface of the photosensitive drum 34 is not charged, and the toner adheres to the entire surface of the photosensitive drum 34 in a solid state. If the toner from the photosensitive drum 34 adheres to the printing medium P from the tip of the printing medium P at this time, the printing medium P may not be discharged from the fixing device 20 and may wind around the fixing roller 21, causing a jam. On the other hand, when the absolute value of the charging bias voltage becomes a voltage higher than the set value, it may discharge from the charging roller 36 into the ID unit 13, causing various mechanisms inside the ID unit 13 to malfunction.

When the voltage setting signal S3 is input from the printer control unit 40, the developing bias circuit 66 outputs a developing bias voltage, which is a negative high voltage of about -250 [V], to the developing roller 32, which is an external load.

When the voltage setting signal S4 is input from the printer control unit 40, the supply bias circuit 68 outputs a supply bias voltage, which is a negative high voltage of about -350 [V], to the toner supply roller 30, which is an external load.

When the voltage setting signal S5 is input from the printer control unit 40, the transfer bias circuit 70 outputs a positive high voltage of about +2000 [V] to the transfer roller 18, which is an external load. The transfer bias circuit 70 also inputs an output voltage signal S6 indicating the output voltage value of the transfer bias voltage to the printer control unit 40. If the absolute value of the transfer bias voltage becomes a voltage lower than a predetermined set value, there is a problem that the toner is not transferred to the print medium P, the waste toner in the ID unit 13 increases, and the toner stored in the waste toner container that stores the waste toner increases. On the other hand, if the absolute value of the transfer bias voltage becomes a voltage higher than the set value, discharge from the transfer roller 18 into the ID unit 13 or the printer 1 may cause the ID unit 13 or the printer 1 to malfunction.

In this embodiment, the charging bias voltage, developing bias voltage, supply bias voltage, and transfer bias voltage are DC voltages, but they may be DC superimposed voltages in which an AC voltage is superimposed on a DC voltage. In the printer 1 according to this embodiment, the charging bias voltage, developing bias voltage, and supply bias voltage are negative high voltages, and the transfer bias voltage is a positive high voltage, but the polarity of the voltages may be reversed.

[5. High-Voltage Circuit Abnormality Detection Processing]
Next, the high voltage circuit abnormality detection procedure RT1, which is a specific procedure for the high voltage circuit abnormality detection process executed by printer control unit 40 to detect an abnormality in high voltage circuit 50 during printing, will be described using the flowcharts in Figures 4 and 5. Printer control unit 40 starts high voltage circuit abnormality detection procedure RT1 and proceeds to step SP1.

In step SP1, the printer control unit 40 checks the output voltage values of the charging bias voltage and the transfer bias voltage by checking the output voltage signal S2 and the output voltage signal S6, and then proceeds to step SP2. In step SP2, the printer control unit 40 determines whether the absolute values of the output voltage values of both the charging bias voltage and the transfer bias voltage are outside the set values and are abnormal. If a positive result is obtained here, this indicates that the output voltage values of both the charging bias voltage and the transfer bias voltage are abnormal at the same time, and in this case the printer control unit 40 proceeds to step SP3 (Figure 5).

In step SP3, the printer control unit 40 determines that because fuse 62 has been blown, the voltage of constant voltage source 54 is not being supplied to high voltage circuit 50, and the output voltage values of both the charging bias voltage and the transfer bias voltage are simultaneously abnormal, and proceeds to step SP4. In step SP4, the printer control unit 40 stops the feeding of print medium P from paper feed cassette 4, controls the print medium P currently being printed until it is completely discharged into paper stacker unit 2A, and proceeds to step SP5. In step SP5, the printer control unit 40 notifies the operator that fuse 62 has been blown by displaying the message "High voltage fuse blown error" on display operation unit 3, and proceeds to step SP19, ending high voltage circuit abnormality detection processing procedure RT1.

On the other hand, if a negative result is obtained in step SP2 (Figure 4), this indicates that although the output voltage values of both the charging bias voltage and the transfer bias voltage are not abnormal at the same time, there is a possibility that the output voltage value of either the charging bias voltage or the transfer bias voltage is abnormal, and in this case the printer control unit 40 proceeds to step SP6.

In step SP6, the printer control unit 40 determines whether the absolute value of only one of the output voltage values, the charging bias voltage or the transfer bias voltage, is outside the set value and is abnormal. If a positive result is obtained here, this indicates that only one of the output voltage values, the charging bias voltage or the transfer bias voltage, is abnormal, and in this case the printer control unit 40 proceeds to step SP7.

In step SP7, the printer control unit 40 judges whether the absolute value of the output voltage value of the transfer bias voltage is lower than the set value. If a negative result is obtained here, this indicates that the absolute value of the output voltage value of the charging bias voltage is lower than the set value, the absolute value of the output voltage value of the charging bias voltage is higher than the set value, or the absolute value of the output voltage value of the transfer bias voltage is higher than the set value, and in this case the printer control unit 40 moves to step SP8. In step SP8, the printer control unit 40 judges whether the absolute value of the output voltage value of the charging bias voltage is abnormal because it is outside the set value. If a positive result is obtained here, this indicates that the absolute value of the output voltage value of the charging bias voltage is lower than the set value, or the absolute value of the output voltage value of the charging bias voltage is higher than the set value, and therefore the output voltage value of the charging bias voltage is abnormal, and in this case the printer control unit 40 moves to step SP9 (Figure 5).

In step SP9, the printer control unit 40 determines that the charging bias circuit 64 in the high-voltage circuit 50 is malfunctioning because the output voltage value of the charging bias voltage is abnormal, and proceeds to step SP10. In step SP10, the printer control unit 40 immediately stops the current printing, and proceeds to step SP11. In step SP11, the printer control unit 40 notifies the operator that the charging bias circuit 64 in the high-voltage circuit 50 is malfunctioning by displaying the message "High-voltage output error. Charging bias circuit abnormality" on the display operation unit 3, and proceeds to step SP19, ending the high-voltage circuit abnormality detection processing procedure RT1.

On the other hand, if a negative result is obtained in step SP8 (Figure 4), this indicates that the absolute value of the output voltage value of the transfer bias voltage is higher than the set value, and therefore the output voltage value of the transfer bias voltage is abnormal, and in this case the printer control unit 40 proceeds to step SP12 (Figure 5).

In step SP12, the printer control unit 40 determines that the transfer bias circuit 70 in the high-voltage circuit 50 is malfunctioning because the absolute value of the output voltage value of the transfer bias voltage is higher than the set value and is therefore abnormal, and proceeds to step SP13. In step SP13, the printer control unit 40 immediately stops the current printing and proceeds to step SP14. In step SP14, the printer control unit 40 notifies the operator that the transfer bias circuit 70 in the high-voltage circuit 50 is malfunctioning by displaying the message "High-voltage output error. Transfer bias circuit abnormality" on the display operation unit 3, and proceeds to step SP19, ending the high-voltage circuit abnormality detection processing procedure RT1.

On the other hand, if a positive result is obtained in step SP7 (Figure 4), this indicates that the absolute value of the output voltage value of the transfer bias voltage is lower than the set value, and therefore the output voltage value of the transfer bias voltage is abnormal, and in this case the printer control unit 40 proceeds to step SP15 (Figure 5).

In step SP15, the printer control unit 40 determines that the transfer bias circuit 70 in the high voltage circuit 50 is malfunctioning because the absolute value of the output voltage value of the transfer bias voltage is lower than the set value and is abnormal, and proceeds to step SP16. In step SP16, the printer control unit 40 stops the feeding of the print medium P from the paper feed cassette 4, controls the print medium P currently being printed until it is completely discharged into the paper stacker unit 2A, and proceeds to step SP17. In step SP17, the printer control unit 40 notifies the operator that the transfer bias circuit 70 in the high voltage circuit 50 is malfunctioning by displaying the message "High voltage output error. Transfer bias circuit abnormality" on the display operation unit 3, and proceeds to step SP19, ending the high voltage circuit abnormality detection processing procedure RT1.

On the other hand, if a negative result is obtained in step SP6 (FIG. 4), this indicates that the output voltage values of both the charging bias voltage and the transfer bias voltage are normal, and the printer control unit 40 then proceeds to step SP18. In step SP18, the printer control unit 40 determines whether printing of the current print job has been completed. If a positive result is obtained here, the printer control unit 40 then proceeds to step SP19 (FIG. 5) and ends the high-voltage circuit abnormality detection processing procedure RT1. On the other hand, if a negative result is obtained in step SP18, the printer control unit 40 then proceeds to step SP1 (FIG. 4) and repeats the above-mentioned processing.

[6. Effects, etc.]
As described above, when the connection cord is shorted to ground, when the external output terminal of the high-voltage circuit 50 is shorted to ground, or when a failure of the high-voltage circuit 50 occurs, the fuse 62 melts. When the fuse 62 melts, the high-voltage circuit 50 cannot output any high-voltage bias voltages, including the charging bias voltage and the transfer bias voltage, and the print result of the print medium P is blank. Therefore, when the fuse 62 melts, the print medium P does not wrap around the fuser 20 due to toner adhesion to the leading edge on the downstream side in the transport direction. Therefore, when the fuse 62 melts, even if the printer 1 controls the print medium P currently being printed until it is completely discharged to the paper stacker unit 2A, the print medium P does not wrap around the fuser 20, so this does not directly lead to a failure of the printer 1 and does not reduce reliability.

In addition, if the printer 1 detects an abnormality in both the charging bias voltage and the transfer bias voltage at the same time, it is highly unlikely that the charging bias circuit 64 and the transfer bias circuit 70 will fail at the same time, so it is likely that this is due to the fuse 62 having blown, rather than a failure of the high-voltage circuit 50.

On the other hand, if the charging bias circuit 64 of the high voltage circuit 50 fails and the absolute value of the charging bias voltage becomes lower than the set value, the surface of the photosensitive drum 34 is not charged and the toner adheres to the entire surface of the photosensitive drum 34. If this toner adheres to the print medium P from the leading edge on the downstream side in the transport direction, the print medium P is more likely to wrap around the fixing device 20. On the other hand, if the charging bias circuit 64 of the high voltage circuit 50 fails and the absolute value of the charging bias voltage becomes higher than the set value, there is a possibility that the charging roller 36 will discharge into the ID unit 13, causing various mechanisms inside the ID unit 13 to fail. For this reason, when the absolute value of the charging bias voltage becomes a voltage different from the set value, it is preferable that the printer 1 immediately stops printing and prevents the print medium P from wrapping around the fixing device 20 and discharging into the ID unit 13, thereby improving reliability.

On the other hand, if the transfer bias circuit 70 of the high voltage circuit 50 fails and the absolute value of the transfer bias voltage becomes higher than the set value, discharge may occur from the transfer roller 18 into the ID unit 13 or into the printer 1, causing the ID unit 13 or the printer 1 to fail. For this reason, when the absolute value of the transfer bias voltage becomes higher than the set value, it is preferable for the printer 1 to immediately stop printing and prevent discharge into the ID unit 13 or into the printer 1, thereby improving reliability.

Furthermore, if the transfer bias circuit 70 of the high voltage circuit 50 fails and the absolute value of the transfer bias voltage becomes lower than the set value, the toner is not transferred to the print medium P, the amount of waste toner in the ID unit 13 increases, and the amount of toner stored in the waste toner container that stores the waste toner also increases. In that case, the print result of the print medium P will be blank or abnormal, but the toner will not adhere to the leading edge of the print medium P downstream in the transport direction and wrap around the fuser 20. Therefore, even if the absolute value of the transfer bias voltage becomes lower than the set value and the printer 1 controls the print medium P currently being printed until it is completely discharged into the paper stacker unit 2A, the print medium P will not wrap around the fuser 20, so this will not directly lead to a failure of the printer 1 and will not reduce reliability.

In response to this, the printer 1 is designed to monitor the charging bias voltage and transfer bias voltage, which are multiple output states in the high-voltage circuit 50, during printing operations.

Specifically, when the printer 1 detects an abnormality in both the charging bias voltage and the transfer bias voltage at the same time, it determines that the fuse 62 has been blown, and after completing the ejection of the print medium P from inside the device housing 2 to the outside, it displays an error screen indicating that the fuse 62 has been blown. Therefore, when the fuse 62 to the high-voltage circuit 50 is blown during a printing operation and a blank page is printed, the printer 1 can prevent the print medium P from remaining inside the printer 1 and causing a jam, which would stop the operation of the printer 1. Therefore, the printer 1 can prevent the user or maintenance personnel from having to take out the print medium P from inside the printer 1, even though it would be no problem to eject the print medium P to the outside of the printer 1 as it is because it is a blank page. This allows the printer 1 to improve convenience.

On the other hand, if the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage, it determines that an abnormality has occurred in the high-voltage circuit 50. Next, if the printer 1 detects an abnormality in the charging bias voltage, it determines that an abnormality has occurred in the charging bias circuit 64 of the high-voltage circuit 50, immediately stops printing, and then displays an error screen indicating that an abnormality has occurred in the charging bias circuit 64 of the high-voltage circuit 50. This allows the printer 1 to prevent the print medium P from wrapping around the fixing device 20 and discharge into the ID unit 13, improving reliability.

On the other hand, the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage, and if the absolute value of the transfer bias voltage is higher than the set value, it determines that an abnormality has occurred in the transfer bias circuit 70 of the high-voltage circuit 50, immediately stops printing, and then displays an error screen indicating that an abnormality has occurred in the transfer bias circuit 70 of the high-voltage circuit 50. This allows the printer 1 to prevent discharge into the ID unit 13 or inside the printer 1, improving reliability.

Furthermore, the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage, and if the absolute value of the transfer bias voltage is lower than the set value, it determines that an abnormality has occurred in the transfer bias circuit 70 of the high-voltage circuit 50, and after completing the ejection of the print medium P from inside the device housing 2 to the outside, displays an error screen indicating that an abnormality has occurred in the transfer bias circuit 70 of the high-voltage circuit 50. Therefore, when the absolute value of the transfer bias voltage becomes lower than the set value during a printing operation, the printer 1 can prevent the operation of the printer 1 from being stopped with the print medium P remaining in the printer 1 and a jam occurring. Therefore, the printer 1 can prevent the user or maintenance person from having to take out the print medium P from inside the printer 1, even though there would have been no problem if it had been ejected outside the printer 1 as it was. This allows the printer 1 to improve convenience.

In this way, the printer 1 can improve convenience while maintaining reliability. Furthermore, the printer 1 can distinguish between a blown fuse 62, a failure of the charging bias circuit 64 in the high-voltage circuit 50, and a failure of the transfer bias circuit 70 in the high-voltage circuit 50, making it easy to identify the location of the failure. As a result, the printer 1 can identify and present to the maintenance personnel the areas of the printer 1 that need maintenance, improving the efficiency of maintenance work.

According to the above configuration, the printer 1 is provided with a charging bias circuit 64 and a transfer bias circuit 70, which are supplied with driving voltage from the same constant voltage source 54 and output to the charging roller 36 and the transfer roller 18 as external loads, and a printer control unit 40 that detects the output state of the charging bias voltage and the transfer bias voltage, which are the output of the charging bias circuit 64 and the transfer bias circuit 70 to the charging roller 36 and the transfer roller 18, respectively. If the printer control unit 40 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage during the printing operation, it stops the transportation of the printing medium P being printed before the ejection is completed, but if it detects an abnormality in both the charging bias voltage and the transfer bias voltage during the printing operation, it ejects the printing medium P in the printer 1.

As a result, if the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage during a printing operation, it determines that there is a failure in the high-voltage circuit 50, and by stopping the transport of the print medium P being printed before it is completely discharged, it is possible to prevent the print medium P from wrapping around the fixing unit 20 and discharging into the ID unit 13 or inside the printer 1; and if the printer 1 detects an abnormality in both the charging bias voltage and the transfer bias voltage during a printing operation, it determines that the fuse 62 has blown, and by discharging the print medium P from within the device housing 2, it is possible to prevent the print medium P from remaining in the device housing 2 and causing a jam.

7. Other embodiments
In the above embodiment, when only the output voltage value of either the charging bias voltage or the transfer bias voltage is abnormal, the system switches between immediately stopping printing and controlling the print medium P currently being printed until it is completely discharged into the paper stacker unit 2A, and changes the content of the error screen, depending on whether the charging bias voltage is abnormal, the absolute value of the transfer bias voltage is higher than the set value, or the absolute value of the transfer bias voltage is lower than the set value. The present invention is not limited to this, and when only the output voltage value of either the charging bias voltage or the transfer bias voltage is abnormal, the system may immediately stop printing and display the content "high voltage output error" on the display operation unit 3 to inform the operator that the high voltage circuit 50 has failed.

In the above-described embodiment, the output voltage signal S2 and the output voltage signal S6 are checked to check the output voltage values of the charging bias voltage and the transfer bias voltage, and the charging bias circuit 64 and the transfer bias circuit 70 are monitored for abnormalities. The present invention is not limited to this, and an output voltage signal indicating the output voltage value of the developing bias voltage from the developing bias circuit 66 may be input to the printer control unit 40, and the printer control unit 40 may check this output voltage signal to monitor for abnormalities in the developing bias circuit 66, or an output voltage signal indicating the output voltage value of the supply bias voltage from the supply bias circuit 68 may be input to the printer control unit 40, and the printer control unit 40 may check this output voltage signal to monitor for abnormalities in the supply bias circuit 68. In this case, similar to the control when monitoring the transfer bias circuit 70, if the absolute value of the output voltage value of the development bias circuit 66 is higher than the set value, printing is immediately stopped and an error screen is displayed indicating that an abnormality has occurred in the transfer bias circuit 70, whereas if the absolute value of the output voltage value of the development bias circuit 66 is lower than the set value, the ejection of the print medium P from inside the device housing 2 to the outside is completed and then an error screen is displayed indicating that an abnormality has occurred in the development bias circuit 66. The same applies to the control when monitoring the supply bias circuit 68.

Furthermore, in the above-described embodiment, a case has been described in which an error screen is displayed on the display operation unit 3. The present invention is not limited to this, and the content of the error may be notified to the operator by various other notification methods, such as outputting a sound indicating the content of the error.

Furthermore, in the above-described embodiment, the present invention has been described as being applied to printer 1, which is a monochrome printer that has one image forming unit 12 corresponding to the color black and performs monochrome printing. The present invention is not limited to this, and may be applied to various image forming devices, such as an image forming device that is a color printer that has four image forming units corresponding to the colors yellow, magenta, cyan, and black and performs color printing, or an image forming device that has three or less image forming units or five or more image forming units.

Furthermore, in the above-mentioned embodiment, the present invention has been described as being applied to the printer 1. However, the present invention is not limited to this, and may be applied to various devices that perform various types of image processing, such as facsimiles, MFPs (multifunction printers), copiers, etc.

Furthermore, the present invention is not limited to the above-mentioned embodiments and other embodiments. In other words, the scope of application of the present invention extends to embodiments in which the above-mentioned embodiments are combined in part or in whole with the above-mentioned other embodiments in any combination. The scope of application of the present invention also extends to cases in which a part of the configuration described in the above-mentioned embodiments and any of the above-mentioned other embodiments is extracted and replaced or diverted with a part of the configuration of any of the above-mentioned embodiments and other embodiments, or a part of the extracted configuration is added to any of the above-mentioned embodiments.

Furthermore, in the above-described embodiment, the printer 1 as an image forming apparatus is configured by the charging bias circuit 64 and the transfer bias circuit 70 as multiple high voltage circuits, and the printer control unit 40 as a control unit. The present invention is not limited to this, and the image forming apparatus may be configured by high voltage circuits and a control unit having various other configurations.

The present invention can be used, for example, in electrophotographic printers.

1: printer, 2: device housing, 2A: paper stacker section, 2B: paper discharge port, 3: display operation section, P: print medium, 4: paper feed cassette, 6: transport path, 8: hopping roller, 9, 10: registration roller, 12: image forming unit, 13: ID unit, 14: toner cartridge, 16: LED head, 18: transfer roller, 20: fuser, 21: fuser roller, 22: backup roller, 24, 25: discharge roller, 30: ...toner supply roller, 32...developing roller, 34...photosensitive drum, 36...charging roller, 40...printer control unit, 42...paper feed motor, 44...ID motor, 46...fixing motor, 48...fixing control unit, 50...high voltage circuit, 54...constant voltage source, 62...fuse, 64...charging bias circuit, 66...developing bias circuit, 68...supply bias circuit, 70...transfer bias circuit, S1, S3, S4, S5...voltage setting signal, S2, S6...output voltage signal.

Claims (11)

A plurality of high voltage circuits each of which is supplied with a driving voltage from the same voltage source and outputs the driving voltage to each of the external loads;
a control unit that detects an output state of each of the plurality of high voltage circuits to the external load,
The control unit is
This image forming apparatus is characterized in that if an abnormality is detected in only one of the outputs of the multiple high-voltage circuits during a printing operation, the transport of the medium being printed is stopped before ejection is completed, and if an abnormality is detected in all of the outputs of the multiple high-voltage circuits during a printing operation, the medium within the apparatus is ejected. The control unit is
2. The image forming apparatus according to claim 1, wherein when an abnormality is detected in only one of the outputs of the plurality of high voltage circuits during a printing operation, it is determined that the high voltage circuit is faulty. The control unit is
The image forming device according to claim 2, wherein if an abnormality is detected in only one of the outputs of the plurality of high-voltage circuits during a printing operation, the transport of the medium being printed is stopped before ejection is completed, and then a message is displayed indicating that the high-voltage circuit has failed. The power supply further includes a fuse disposed in the power supply;
The control unit is
The image forming apparatus according to claim 1 , wherein when an abnormality is detected in all of the outputs of the plurality of high voltage circuits during a printing operation, it is determined that the fuse has been blown. The control unit is
The image forming apparatus according to claim 4 , wherein when an abnormality is detected in all of the outputs of the plurality of high voltage circuits during a printing operation, a message is displayed indicating that the fuse has been blown. the plurality of high voltage circuits are a charging bias circuit and a transfer bias circuit,
the external load is a charging roller and a transfer roller,
The control unit is
6. An image forming apparatus as described in claim 1, further comprising: a detecting unit that detects an output state of the output from the charging bias circuit to the charging roller and an output state of the output from the transfer bias circuit to the transfer roller; and if an abnormality is detected in only one of the output of the charging bias circuit and the output of the transfer bias circuit during a printing operation, the transport of the medium being printed is stopped before ejection is completed; whereas if an abnormality is detected in both the output of the charging bias circuit and the output of the transfer bias circuit during a printing operation, the medium within the apparatus is ejected. The control unit is
7. The image forming apparatus according to claim 6, wherein, during a printing operation, if the output of the charging bias circuit is higher or lower than a set value, or if the output of the transfer bias circuit is higher than a set value, transport of the medium being printed is stopped before completion of ejection. The control unit is
8. The image forming apparatus according to claim 7, characterized in that, if the output of the charging bias circuit is higher or lower than a set value during a printing operation, the transport of the medium being printed is stopped before completion of ejection, and then a message indicating that the charging bias circuit is faulty is displayed. The control unit is
The image forming apparatus according to claim 7, characterized in that, if during a printing operation, the output of the transfer bias circuit is higher than a set value, the transport of the medium being printed is stopped before completion of ejection, and then a message indicating that the transfer bias circuit is faulty is displayed. The control unit is
7. The image forming apparatus according to claim 6, wherein, during a printing operation, if the output of the transfer bias circuit is lower than a set value, the medium within the apparatus is discharged. The control unit is
11. The image forming apparatus according to claim 10, wherein, when an output of the transfer bias circuit is lower than a set value during a printing operation, a message indicating that the transfer bias circuit is out of order is displayed.

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