Image forming apparatus

Abstract

To improve convenience while maintaining reliability.SOLUTION: A printer 1 is provided with: an electrification bias circuit 64 and a transfer bias circuit 70 that are supplied with voltage for driving from the same constant voltage source 54 and output voltage to an electrifying roller 36 and a transfer roller 18; and a printer control unit 40 that detects the state of output of an electrification bias voltage and a transfer bias voltage that are output from the electrification bias circuit 64 and the transfer bias circuit 70 to the electrifying roller 36 and the transfer roller 18, respectively. When detecting an abnormality in either one of the electrification bias voltage and the transfer bias voltage during a printing operation, the printer control unit 40 stops conveyance of a print medium P being printed before the completion of ejection, and on the other hand, when detecting an abnormality in both of the electrification bias voltage and the transfer bias voltage during the printing operation, ejects the printing medium P inside the printer 1.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and is suitable for application to, for example, an electrophotographic image forming apparatus.

Background Art

[0002] Conventionally, as an image forming apparatus (also called a printer), based on an image supplied from a computer device or the like, a toner image is formed by an image forming unit using toner (also called a developer), transferred to a medium such as paper, and heat and pressure are applied thereto in a fixing unit to perform a printing process by fixing it. Such an image forming apparatus has been widely spread, and some detect the melting of a fuse in a high-voltage circuit and the failure of a high-voltage transformer circuit (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such an image forming apparatus, it is desired to improve convenience while maintaining reliability.

[0005] The present invention has been made in consideration of the above points, and intends to propose an image forming apparatus capable of improving convenience while maintaining reliability.

Means for Solving the Problems

[0006] In order to solve such problems, in the image forming apparatus of the present invention, a plurality of high-voltage circuits to which driving voltages are supplied from the same voltage source and output to respective external loads, and a control unit for detecting an output state of an output to an external load of each of the plurality of high-voltage circuits are provided. When the control unit detects an abnormality in only one of the outputs of the plurality of high-voltage circuits during a printing operation, the control unit stops the conveyance of the medium being printed before the discharge is completed, while when the control unit detects an abnormality in all of the outputs of the plurality of high-voltage circuits during the printing operation, the control unit discharges the medium in the apparatus.

[0007] According to the present invention, when an abnormality in only one of a plurality of outputs is detected during a printing operation, by stopping the conveyance of the medium being printed before the discharge is completed, it is possible to prevent abnormal conveyance of the medium and discharge, and when an abnormality in all of the plurality of outputs is detected during the printing operation, by discharging the medium in the image forming apparatus, it is possible to prevent the medium from remaining in the image forming apparatus and causing a jam.

Advantages of the Invention

[0008] According to the present invention, it is possible to realize an image forming apparatus that can improve convenience while maintaining reliability.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings. [1. Configuration of Image Forming Apparatus] As shown in FIG. 1, the printer 1 is a monochrome electrophotographic printer that performs monochrome printing, and prints a desired monochrome image on a printing medium P, which is a sheet of paper of a size such as A3 or A4. This printer 1 is controlled by a printer control unit 40. When the printer control unit 40 receives printing data from the outside via an interface (not shown) such as USB (Universal Serial Bus) or LAN (Local Area Network), it starts printing by controlling each part of the printer 1.

[0011] On the front upper surface outside the apparatus housing 2, a display operation unit 3 is provided. The display operation unit 3 is composed of a combination of a predetermined display panel and a predetermined operation button. The display panel of the display operation unit 3 displays the operating status of the printer 1, and displays, for example, the detection of an abnormality and the location thereof. The operation button of the display operation unit 3 receives an instruction regarding printing, for example, via a pressing operation by an operator.

[0012] Inside the apparatus housing 2, each part is arranged along a conveyance path 6 for conveying the printing medium P. At the lower part inside the apparatus housing 2, a paper feed cassette 4 for accommodating the printing medium P is provided. A pair of hopping rollers 8 for feeding the printing medium P from the paper feed cassette 4 to the conveyance path 6 are provided near the upper front side of the paper feed cassette 4. A pair of registration rollers 9 and 10 are provided on the downstream side in the conveyance direction of the printing medium P from the hopping rollers 8 in the conveyance path 6 to correct the skew of the printing medium P fed by the hopping rollers 8 and send it to the image forming unit 12 at a predetermined timing.

[0013] One image forming unit 12 corresponding to the color of the developer (for example, black (K) toner) handled by the printer 1 is provided near the upper front side inside the apparatus housing 2.

[0014] The image forming unit 12 forms an electrostatic latent image on the surface of the photosensitive drum 34 by irradiating and exposing the surface of the photosensitive drum 34 with light from an LED (Light Emitting Diode) head 16. After that, a toner image is formed on the surface of the photosensitive drum 34 by attaching toner supplied from the toner cartridge 14 to the electrostatic latent image.

[0015] Furthermore, below the image forming unit 12 inside the apparatus housing 2, a transfer roller 18 disposed opposite to the lower side of the photosensitive drum 34 is provided. When a transfer bias voltage, which is a positive high voltage, is applied to the transfer roller 18 from a transfer bias circuit 70 (Fig. 3), the transfer roller 18 charges the printing medium P to a polarity opposite to that of the toner when the printing medium P passes between the photosensitive drum 34 and the transfer roller 18. Thereby, the transfer roller 18 transfers the toner image formed on the photosensitive drum 34 to the printing medium P.

[0016] Furthermore, a fixing device 20 is provided on the downstream side (i.e., the rear side) in the conveyance direction of the image forming unit 12 inside the apparatus housing 2. The fixing device 20 includes a fixing roller 21 having a halogen heater disposed above the conveyance path 6, and a backup roller 22 disposed opposite to the lower side of the fixing roller 21 with the conveyance path 6 interposed therebetween. This fixing device 20 heats the fixing roller 21 to a fixable temperature by the electric power input to the halogen heater, and fixes the toner image transferred to the printing medium P by the transfer roller 18 onto the printing medium P by heating and pressurizing with these fixing roller 21 and backup roller 22.

[0017] Furthermore, a pair of discharge rollers 24 for conveying the printing medium P to the paper discharge port 2B are provided on the conveyance path 6 between the fixing device 20 and the paper discharge port 2B inside the apparatus housing 2. Further, on the downstream side in the conveyance direction from the discharge rollers 24 in the conveyance path 6, a pair of discharge rollers 25 for discharging the paper from the paper discharge port 2B to the paper stacker unit 2A for stacking the printing medium P are provided.

[0018] [2. Configuration of Image Forming Unit] The image forming unit 12 is composed of an ID unit 13 and a toner cartridge 14. The toner cartridge 14 stores toner as a developer inside and is configured to be detachable from the ID unit 13.

[0019] The ID unit 13 incorporates a toner supply roller 30, a developing roller 32, a photosensitive drum 34, and a charging roller 36. These toner supply roller 30, developing roller 32, photosensitive drum 34, and charging roller 36 are each configured in a columnar shape with their central axes along the left - right direction.

[0020] The toner supply roller 30 supplies toner to the developing roller 32 when a supply bias voltage, which is a negative high voltage, is applied from a supply bias circuit 68 (Fig. 3). The developing roller 32 supplies toner to the photosensitive drum 34 when a developing bias voltage, which is a negative high voltage, is applied from a developing bias circuit 66 (Fig. 3).

[0021] The photosensitive drum 34 has a thin - film - like charge generation layer and charge transport layer sequentially formed on its circumferential side surface and can be charged. When the ID unit 13 is mounted on the printer 1, the lower surface of the photosensitive drum 34 is brought into contact with the printing medium P. The charging roller 36 charges the surface of the photosensitive drum 34 when a charging bias voltage, which is a negative high voltage, is applied from a charging bias circuit 64 (Fig. 3).

[0022] The LED head 16 is located above the photosensitive drum 34. The LED head 16 has a plurality of light - emitting element chips arranged linearly along the left - right direction and causes each light - emitting element to emit light in a light - emitting pattern based on an image data signal supplied from the printer control unit 40.

[0023] In such a configuration, the ID unit 13 rotates the toner supply roller 30, the developing roller 32, and the charging roller 36, and rotates the photosensitive drum 34 by being supplied with a driving force from the ID motor 44 (Fig. 2). Further, 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.

[0024] The toner supply roller 30 adheres toner to its circumferential side surface by being charged, and adheres this toner to the circumferential side surface of the developing roller 32 by rotating. The developing roller 32 brings its circumferential side surface into contact with the circumferential side surface of the photosensitive drum 34 with the toner adhering in a thin film state.

[0025] On the other hand, the charging roller 36 uniformly charges the circumferential side surface of the photosensitive drum 34 by coming into contact with the photosensitive drum 34 in a charged state. The LED head 16 emits light at predetermined time intervals in a light emission pattern based on the image data signal supplied from the printer control unit 40, thereby sequentially exposing the charged photosensitive drum 34. As a result, an electrostatic latent image for adhering a charged toner image is sequentially formed on the exposed portions on the circumferential side surface near the upper end of the photosensitive drum 34.

[0026] Subsequently, the photosensitive drum 34 rotates to bring the portion where the electrostatic latent image is formed into contact with the developing roller 32. As a result, toner adheres to the circumferential side 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 further rotates to reach the toner image near the lower end of the photosensitive drum 34.

[0027] At this time, the printer 1 causes the print medium P to reach below the ID unit 13, and applies a transfer bias voltage to the transfer roller 18 to charge it with characteristics opposite to those of the toner. For this reason, the ID unit 13 sandwiches the print medium P between the portion of the photosensitive drum 34 where the toner image is formed and the charged transfer roller 18, and transfers this toner image to the print medium P.

[0028] [Configuration of Printer Control Unit] As shown in FIG. 2, the printer control unit 40 has a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., which are not shown. By executing a predetermined program read from the ROM etc. by the CPU, various processes are performed to carry out a printing operation. 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.

[0029] The paper feed motor 42 is a stepping motor, and feeds and conveys the printing medium P by rotationally driving the hopping roller 8 and the resist rollers 9 and 10. The ID motor 44 is a brushless DC motor, and rotationally drives the ID unit 13 and the transfer roller 18. The LED head 16 exposes the surface of the charged photosensitive drum 34. The fixing motor 46 is a brushless DC motor, and rotationally drives 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 device 20. The high-voltage circuit 50 is a circuit that generates a high voltage for performing charging, development, and transfer, which are functions of the ID unit 13.

[0030] [Configuration of High-Voltage Circuit] As shown in FIG. 3, the high-voltage circuit 50 is connected to a constant voltage source 54 and 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 substrate separate from the high-voltage circuit 50, and blows when a short circuit to the ground of the connection cord, a short circuit to the ground of the external output terminal of the high-voltage circuit 50, a failure of the high-voltage circuit 50, etc. occur. When the fuse 62 blows, the high-voltage circuit 50 cannot output all the high-voltage bias voltages, so the printing result of the printing medium P becomes a blank paper state.

[0031] 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.

[0032] When a voltage setting signal S1 is input from the printer control unit 40 to the charging bias circuit 64, 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. Also, the charging bias circuit 64 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 lower than a predetermined set value, the surface of the photosensitive drum 34 is not charged, and toner adheres uniformly to the entire surface of the photosensitive drum 34. At this time, if toner adheres to the printing medium P from the leading edge of the printing medium P from the photosensitive drum 34, the printing medium P may be wound around the fixing roller 21 without being discharged from the fixing unit 20, and a jam may occur. On the other hand, when the absolute value of the charging bias voltage becomes higher than the set value, there is a possibility of discharging from the charging roller 36 to the inside of the ID unit 13 and causing various mechanisms inside the ID unit 13 to malfunction.

[0033] When a voltage setting signal S3 is input from the printer control unit 40 to the developing bias circuit 66, 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.

[0034] When a voltage setting signal S4 is input from the printer control unit 40 to the supply bias circuit 68, 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.

[0035] When a voltage setting signal S5 is input from the printer control unit 40 to the transfer bias circuit 70, the transfer bias circuit 70 outputs a transfer bias voltage, which is a positive high voltage of about +2000 [V], to the transfer roller 18, which is an external load. Further, the transfer bias circuit 70 inputs an output voltage signal S6 indicating the output voltage value of the transfer bias voltage to the printer control unit 40. When the absolute value of the transfer bias voltage becomes lower than a predetermined set value, 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 for storing the waste toner also increases. On the other hand, when the absolute value of the transfer bias voltage becomes higher than the set value, there is a possibility of discharging from the transfer roller 18 to the ID unit 13 or inside the printer 1, causing a failure in the ID unit 13 or the printer 1.

[0036] In this embodiment, although the charging bias voltage, the developing bias voltage, the supply bias voltage, and the transfer bias voltage are DC voltages, they may be DC superimposed voltages in which an AC voltage is superimposed on the DC voltage. Further, in the printer 1 according to this embodiment, the charging bias voltage, the developing bias voltage, and the supply bias voltage are negative high voltages, and the transfer bias voltage is a positive high voltage, but the positive and negative of the voltage may be reversed.

[0037] [5. High-Voltage Circuit Abnormality Detection Processing] Next, the specific processing procedure of the high-voltage circuit abnormality detection processing procedure RT1, which is the processing for detecting an abnormality in the high-voltage circuit 50 during printing executed by the printer control unit 40, will be described with reference to the flowcharts of FIGS. 4 and 5. The printer control unit 40 starts the high-voltage circuit abnormality detection processing procedure RT1 and moves to step SP1.

[0038] 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 deviate from the set values and are abnormal. If an affirmative 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. At this time, the printer control unit 40 proceeds to step SP3 (Fig. 5).

[0039] In step SP3, since the fuse 62 is blown, the printer control unit 40 determines that the voltage of the constant voltage source 54 is not supplied to the high voltage circuit 50, and the output voltage values of both the charging bias voltage and the transfer bias voltage are abnormal at the same time, and then proceeds to step SP4. In step SP4, the printer control unit 40 stops the feeding of the printing medium P from the paper feed cassette 4, and controls until the currently printing printing medium P is completely discharged to the paper stacker unit 2A, and then proceeds to step SP5. In step SP5, the printer control unit 40 causes the display operation unit 3 to display the content of "High voltage fuse blown error", thereby notifying the operator that the fuse 62 is blown, and then proceeds to step SP19 to end the high voltage circuit abnormality detection processing procedure RT1.

[0040] On the other hand, if a negative result is obtained in step SP2 (Fig. 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. At this time, the printer control unit 40 proceeds to step SP6.

[0041] In step SP6, the printer control unit 40 determines whether the absolute value of only one of the output voltage values of the charging bias voltage or the transfer bias voltage deviates from the set value and is abnormal. If an affirmative result is obtained here, this indicates that only one of the output voltage values of the charging bias voltage or the transfer bias voltage is abnormal. At this time, the printer control unit 40 moves to step SP7.

[0042] In step SP7, the printer control unit 40 determines 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. At this time, the printer control unit 40 moves to step SP8. In step SP8, the printer control unit 40 determines whether the absolute value of the output voltage value of the charging bias voltage deviates from the set value and is abnormal. If an affirmative 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, so the output voltage value of the charging bias voltage is abnormal. At this time, the printer control unit 40 moves to step SP9 (Figure 5).

[0043] In step SP9, since the output voltage value of the charging bias voltage is abnormal, the printer control unit 40 determines that the charging bias circuit 64 in the high-voltage circuit 50 is faulty and moves to step SP10. In step SP10, the printer control unit 40 immediately stops the current printing and moves to step SP11. In step SP11, the printer control unit 40 causes the display operation unit 3 to display the content "High-voltage output error. Charging bias circuit abnormality", thereby prompting the operator that the charging bias circuit 64 in the high-voltage circuit 50 is faulty, and then moves to step SP19 to end the high-voltage circuit abnormality detection processing procedure RT1.

[0044] On the other hand, if a negative result is obtained in step SP8 (Fig. 4), this indicates that the absolute value of the output voltage value of the transfer bias voltage is higher than the set value, meaning that the output voltage value of the transfer bias voltage is abnormal. At this time, the printer control unit 40 moves to step SP12 (Fig. 5).

[0045] In step SP12, since the absolute value of the output voltage value of the transfer bias voltage is higher than the set value and abnormal, the printer control unit 40 determines that the transfer bias circuit 70 in the high-voltage circuit 50 is faulty and moves to step SP13. In step SP13, the printer control unit 40 immediately stops the current printing and moves to step SP14. In step SP14, the printer control unit 40 causes the display operation unit 3 to display the message "High-voltage output error. Transfer bias circuit abnormality", thereby notifying the operator that the transfer bias circuit 70 in the high-voltage circuit 50 is faulty, and then moves to step SP19 to end the high-voltage circuit abnormality detection processing procedure RT1.

[0046] On the other hand, if an affirmative result is obtained in step SP7 (Fig. 4), this indicates that the absolute value of the output voltage value of the transfer bias voltage is lower than the set value, meaning that the output voltage value of the transfer bias voltage is abnormal. At this time, the printer control unit 40 moves to step SP15 (Fig. 5).

[0047] In step SP15, since the absolute value of the output voltage value of the transfer bias voltage is lower than the set value and abnormal, the printer control unit 40 determines that the transfer bias circuit 70 in the high-voltage circuit 50 is faulty and moves to step SP16. In step SP16, the printer control unit 40 stops the feeding of the printing medium P from the paper feed cassette 4 and controls until the currently printed printing medium P is completely discharged to the paper stacker unit 2A, and then moves to step SP17. In step SP17, the printer control unit 40 causes the display operation unit 3 to display the message "High-voltage output error. Transfer bias circuit abnormality", thereby notifying the operator that the transfer bias circuit 70 in the high-voltage circuit 50 is faulty, and then moves to step SP19 to end the high-voltage circuit abnormality detection processing procedure RT1.

[0048] 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. At this time, the printer control unit 40 moves to step SP18. In step SP18, the printer control unit 40 determines whether the printing of the current print job has been completed. If an affirmative result is obtained here, the printer control unit 40 then moves 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 moves to step SP1 (Fig. 4) and repeats the above-described processing.

[0049] [6. Effects, etc.] As described above, when a short circuit to ground of the connection cord, a short circuit to ground of the external output terminal of the high-voltage circuit 50, or a failure of the high-voltage circuit 50 occurs, the fuse 62 blows. When the fuse 62 blows, the high-voltage circuit 50 cannot output all high-voltage bias voltages including the charging bias voltage and the transfer bias voltage. Therefore, the printing result of the printing medium P becomes a blank state. For this reason, when the fuse 62 blows, toner adhesion to the leading end on the downstream side in the conveyance direction of the printing medium P does not cause winding around the fixing device 20. Thus, when the fuse 62 blows, even if the printer 1 controls until the currently printed printing medium P is completely discharged to the paper stacker unit 2A, the printing medium P will not wind around the fixing device 20, so it is not directly related to a failure of the printer 1 and the reliability does not decrease.

[0050] Also, when the printer 1 simultaneously detects abnormalities in both the charging bias voltage and the transfer bias voltage, it is considered that this is because the fuse 62 has blown rather than a failure of the high-voltage circuit 50, since the possibility that the charging bias circuit 64 and the transfer bias circuit 70 both fail simultaneously is extremely low.

[0051] On the one hand, when 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 toner adheres to the entire surface of the photosensitive drum 34. If this toner adheres to the leading edge on the downstream side in the conveyance direction of the print medium P, there is a high possibility that the print medium P will wind around the fuser 20. On the other hand, when 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 of discharging from the charging roller 36 to the inside of the ID unit 13 and causing various mechanisms inside the ID unit 13 to fail. Therefore, when the absolute value of the charging bias voltage becomes a voltage different from the set value, it is preferable for the printer 1 to immediately stop printing and prevent the print medium P from winding around the fuser 20 and discharging to the inside of the ID unit 13, thereby improving reliability.

[0052] On the other hand, when 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, there is a possibility of discharging from the transfer roller 18 to the inside of the ID unit 13 or the printer 1 and causing the ID unit 13 or the printer 1 to fail. Therefore, 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 discharging to the inside of the ID unit 13 or the printer 1, thereby improving reliability.

[0053] On the other hand, when the transfer bias circuit 70 of the high-voltage circuit 50 malfunctions and the absolute value of the transfer bias voltage becomes lower than the set value, 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 for storing the waste toner also increases. However, in that case, although the printing result of the print medium P is blank or abnormal, the toner does not adhere to the leading end on the downstream side in the transport direction of the print medium P and does not wrap around the fixing device 20. Therefore, when the absolute value of the transfer bias voltage becomes lower than the set value, even if the printer 1 controls until the currently printed print medium P is completely discharged to the paper stacker unit 2A, the print medium P cannot wrap around the fixing device 20, so it is not directly related to the failure of the printer 1 and the reliability does not decrease.

[0054] In contrast, during the printing operation, the printer 1 monitors the charging bias voltage and the transfer bias voltage, which are multiple output states in the high-voltage circuit 50.

[0055] Specifically, when the printer 1 simultaneously detects abnormalities in both the charging bias voltage and the transfer bias voltage, it determines that the fuse 62 has blown, completes the discharge of the print medium P from the inside of the device housing 2 to the outside, and then displays an error screen indicating that the fuse 62 has blown. For this reason, when the fuse 62 to the high-voltage circuit 50 blows during the printing operation and results in blank printing, the printer 1 can prevent the operation of the printer 1 from stopping with the print medium P remaining in the printer 1 and a jam occurring. Therefore, the printer 1 can prevent the user or maintenance personnel from having to take the trouble of removing the print medium P, which should have been discharged outside the printer 1 without problems because of blank printing, from inside the printer 1. As a result, the printer 1 can improve convenience.

[0056] On the one hand, when the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage, it is configured to determine that an abnormality has occurred in the high-voltage circuit 50. Subsequently, when 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. Thereby, the printer 1 can prevent the printing medium P from being wound around the fixing device 20 and discharge inside the ID unit 13, and can improve the reliability.

[0057] On the other hand, when the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage and 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. Thereby, the printer 1 can prevent discharge inside the ID unit 13 and the printer 1 itself, and can improve the reliability.

[0058] Furthermore, when the printer 1 detects an abnormality in only one of the charging bias voltage or the transfer bias voltage and 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, completes the discharge of the printing medium P from the inside of the device housing 2 to the outside, and then displays an error screen indicating that an abnormality has occurred in the transfer bias circuit 70 of the high-voltage circuit 50. For this reason, when the absolute value of the transfer bias voltage becomes lower than the set value during the printing operation, the printer 1 can prevent the operation of the printer 1 from stopping with the printing medium P remaining inside the printer 1 and a jam occurring. Therefore, the printer 1 can prevent the user or the maintenance staff from having to take the trouble of taking out the printing medium P that should have been discharged outside the printer 1 without any problem from inside the printer 1. Thereby, the printer 1 can improve the convenience.

[0059] In this way, the printer 1 can improve convenience while maintaining reliability. Also, since the printer 1 can distinguish between the fusing of the fuse 62, the failure of the charging bias circuit 64 in the high-voltage circuit 50, and the failure of the transfer bias circuit 70 in the high-voltage circuit 50, it becomes easy to identify the location of the failure. Therefore, the printer 1 can identify and present to the maintenance staff the locations in the printer 1 that need to be maintained, and can improve the efficiency of the maintenance work.

[0060] According to the above configuration, the printer 1 is provided with a charging bias circuit 64 and a transfer bias circuit 70 that output a driving voltage from the same constant voltage source 54 to the charging roller 36 and the transfer roller 18 as external loads, and a printer control unit 40 that detects the output states of the charging bias voltage and the transfer bias voltage, which are the outputs to the charging roller 36 and the transfer roller 18 of the charging bias circuit 64 and the transfer bias circuit 70, respectively. When 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 conveyance of the printing medium P being printed before the discharge is completed. On the other hand, when the printer control unit 40 detects abnormalities in both the charging bias voltage and the transfer bias voltage during the printing operation, it discharges the printing medium P inside the printer 1.

[0061] Thereby, when the printer 1 detects an abnormality in only one of the charging bias voltage and the transfer bias voltage during the printing operation, it determines that there is a failure in the high-voltage circuit 50, and by stopping the conveyance of the printing medium P being printed before the discharge is completed, it can prevent the printing medium P from being wound around the fixing device 20 and from discharging into the ID unit 13 or inside the printer 1. Also, when the printer 1 detects abnormalities in both the charging bias voltage and the transfer bias voltage during the printing operation, it determines that the fuse 62 has blown, and by discharging the printing medium P inside the device housing 2, it can prevent the printing medium P from remaining inside the device housing 2 and causing a jam.

[0062] [7. Other Embodiments] In the above-described embodiment, when only the output voltage value of either the charging bias voltage or the transfer bias voltage is abnormal, 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 printing is immediately stopped, or the control is switched to control until the currently printed print medium P is completely discharged to the paper stacker unit 2A, and the case where the content of the error screen is changed has been described. The present invention is not limited to this. When only the output voltage value of either the charging bias voltage or the transfer bias voltage is abnormal, the printing may be immediately stopped, and the content "high voltage output error" may be displayed on the display operation unit 3 to prompt the operator that the high voltage circuit 50 is malfunctioning.

[0063] Also, in the above-described embodiment, by checking the output voltage signal S2 and the output voltage signal S6, the output voltage values of the charging bias voltage and the transfer bias voltage are checked, and the case of monitoring whether an abnormality has occurred in the charging bias circuit 64 and the transfer bias circuit 70 has been described. The present invention is not limited to this. An output voltage signal indicating the output voltage value of the developing bias voltage is input from the developing bias circuit 66 to the printer control unit 40, and the printer control unit 40 checks this output voltage signal to monitor whether an abnormality has occurred in the developing bias circuit 66, or an output voltage signal indicating the output voltage value of the supply bias voltage is input from the supply bias circuit 68 to the printer control unit 40, and the printer control unit 40 checks this output voltage signal to monitor whether an abnormality has occurred in the supply bias circuit 68. In that case, similar to the control when monitoring the transfer bias circuit 70, when the absolute value of the output voltage value of the developing bias circuit 66 is higher than the set value, the printing is immediately stopped and then an error screen indicating that an abnormality has occurred in the transfer bias circuit 70 is displayed. On the other hand, when the absolute value of the output voltage value of the developing bias circuit 66 is lower than the set value, after completing the discharge of the print medium P from the inside of the apparatus housing 2 to the outside, an error screen indicating that an abnormality has occurred in the developing bias circuit 66 may be displayed. The same applies to the control for monitoring the supply bias circuit 68.

[0064] Furthermore, in the above-described embodiments, the case where an error screen is displayed on the display operation unit 3 has been described. 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 voice indicating the content of the error.

[0065] Furthermore, in the above-described embodiments, the case where the present invention is applied to the printer 1, which is a monochrome printer having one image forming unit 12 corresponding to the color black and performing monochrome printing, has been described. The present invention is not limited to this, and for example, the present invention may be applied to various image forming apparatuses such as a color printer having four image forming units corresponding to each of the colors yellow, magenta, cyan, and black and performing color printing, and an image forming apparatus having three or less or five or more image forming units.

[0066] Furthermore, in the above-described embodiments, the case where the present invention is applied to the printer 1 has been described. The present invention is not limited to this, and for example, the present invention may be applied to various devices that perform various processes related to images, such as a facsimile machine, an MFP (MultiFunction Printer), and a copying machine.

[0067] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments. That is, the scope of application of the present invention extends to embodiments in which any one or more of the above-described embodiments and the above-described other embodiments are arbitrarily combined. Also, the present invention applies when a part of the configuration described in any of the above-described embodiments and the above-described other embodiments is extracted and replaced or diverted with a part of the configuration of any of the above-described embodiments and the above-described other embodiments, or when a part of the extracted configuration is added to any of the embodiments.

[0068] Furthermore, in the above-described embodiments, the case where the printer 1 as an image forming apparatus is configured by the charging bias circuit 64 and the transfer bias circuit 70 as a plurality of high-voltage circuits and the printer control unit 40 as a control unit has been described. The present invention is not limited to this, and an image forming apparatus may be configured by a high-voltage circuit having various other configurations and a control unit.

Industrial Applicability

[0069] The present invention can be used, for example, in an electrophotographic printer.

Explanation of Signs

[0070] 1... Printer, 2... Apparatus housing, 2A... Paper stacker unit, 2B... Paper discharge port, 3... Display operation unit, P... Printing medium, 4... Paper feed cassette, 6... Conveyor 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... Fixer, 21... Fixing 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

1. A plurality of high-voltage circuits that are driven by the same voltage source and output a driving voltage to respective external loads; A control unit that detects an output state of an output to the external load of each of the plurality of high-voltage circuits; and having: The control unit: When detecting an abnormality in only one of the outputs of the plurality of high-voltage circuits during a printing operation, stops the conveyance of the medium being printed before the discharge is completed, while when detecting an abnormality in all of the outputs of the plurality of high-voltage circuits during a printing operation, discharges the medium in the apparatus. An image forming apparatus characterized by the above.

2. The control unit: When detecting an abnormality in only one of the outputs of the plurality of high-voltage circuits during a printing operation, determines that there is a failure in the high-voltage circuit. The image forming apparatus according to claim 1.

3. The control unit: When detecting an abnormality in only one of the outputs of the plurality of high-voltage circuits during a printing operation, after stopping the conveyance of the medium being printed before the discharge is completed, presents content indicating that the high-voltage circuit has failed. The image forming apparatus according to claim 2.

4. Further having a fuse provided in the voltage source; The control unit: When detecting an abnormality in all of the outputs of the plurality of high-voltage circuits during a printing operation, determines that the fuse has blown. The image forming apparatus according to claim 1.

5. The control unit: When detecting an abnormality in all of the outputs of the plurality of high-voltage circuits during a printing operation, presents content indicating that the fuse has blown. The image forming apparatus according to claim 4.

6. The plurality of high-voltage circuits are a charging bias circuit and a transfer bias circuit; The external loads are a charging roller and a transfer roller; The control unit: Detects an output state of an output from the charging bias circuit to the charging roller and an output state of an output from the transfer bias circuit to the transfer roller, and when detecting an abnormality in only one of the output of the charging bias circuit and the output of the transfer bias circuit during a printing operation, stops the conveyance of the medium being printed before the discharge is completed, while when detecting an abnormality in both the output of the charging bias circuit and the output of the transfer bias circuit during a printing operation, discharges the medium in the apparatus. The image forming apparatus according to any one of claims 1 to 5, characterized by the above.

7. The control unit: During the printing operation, if the output of the charging bias circuit is higher or lower than the set value, or if the output of the transfer bias circuit is higher than the set value, stop the conveyance of the medium being printed before the discharge is completed. The image forming apparatus according to claim 6, characterized in that.

8. The control unit, During the printing operation, if the output of the charging bias circuit is higher or lower than the set value, after stopping the conveyance of the medium being printed before the discharge is completed, present the content indicating that the charging bias circuit is faulty. The image forming apparatus according to claim 7, characterized in that.

9. The control unit, During the printing operation, if the output of the transfer bias circuit is higher than the set value, after stopping the conveyance of the medium being printed before the discharge is completed, present the content indicating that the transfer bias circuit is faulty. The image forming apparatus according to claim 7, characterized in that.

10. The control unit, During the printing operation, if the output of the transfer bias circuit is lower than the set value, discharge the medium in the apparatus. The image forming apparatus according to claim 6, characterized in that.

11. The control unit, During the printing operation, if the output of the transfer bias circuit is lower than the set value, present the content indicating that the transfer bias circuit is faulty. The image forming apparatus according to claim 10, characterized in that.

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