JP2013097095A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can control rotation of a polygon mirror even when attachment such as dust floating in the apparatus is attached onto a reflection surface of the polygon mirror.SOLUTION: When it is determined that lack of a BD signal is periodically detected, an image forming apparatus controls rotation of a polygon mirror 13 at least during a period of lack of the BD signal by using a prediction signal.

Description

  The present invention relates to an image forming apparatus such as a laser printer.

  Conventionally, in an image forming apparatus such as a laser printer, laser light deflected by a polygon mirror is detected by a BD sensor, and a BD signal corresponding to the deflection period of the laser light is output. Then, the lighting start timing of the laser light modulated by the image data is controlled using the BD signal. In such a laser printer, when the laser beam hits dust floating in the apparatus, it sometimes scatters and the output of the BD signal is lost. In this way, if a BD error such as a missing BD signal occurs during printing and the lighting start timing is incorrect, printing cannot be performed properly, and printing must be performed again. Therefore, in the image forming apparatus described in Patent Document 1, when the BD signal is lost, the pseudo BD signal output at the same timing as the BD signal is used to compensate for the loss of the BD signal so that the operation is not hindered. Is disclosed. Further, in the image forming apparatus described in Patent Document 1, there are many missing BD signals, and if the predetermined number of detected BD signals is not reached within a predetermined time, the probability of failure is high and it is determined as abnormal.

Japanese Patent Laid-Open No. 7-242026

  However, in the image forming apparatus described in Patent Document 1, even if a deposit such as dust floating in the apparatus adheres to the reflection surface of the polygon mirror and the BD signal is not properly output, Since the predetermined number of detected BD signals is not reached within a predetermined time, it is determined as abnormal. Therefore, although the user wants to continue the operation of the image forming apparatus as much as possible, the rotation of the polygon mirror is controlled. There is a problem that the operation of the image forming apparatus cannot be continued.

  The present invention has been made to solve the above-described problems, and its purpose is to rotate the polygon mirror even if adhering substances such as dust floating in the apparatus adhere to the reflecting surface of the polygon mirror. An object of the present invention is to provide an image forming apparatus capable of controlling the above.

  In order to achieve this object, an image forming apparatus according to claim 1 receives a laser beam output unit for outputting laser beam, a polygon mirror for deflecting the laser beam, and a laser beam deflected by the polygon mirror. Then, an optical sensor that outputs a light reception signal, a control unit that controls the rotation of the polygon mirror using the light reception signal, a prediction signal output unit that outputs a prediction signal instead of the light reception signal, and a lack of the light reception signal A missing detection unit to detect, and a determination unit to determine whether or not the loss has been detected periodically, and the control unit determines that the loss has been detected periodically by the determination unit In at least the missing portion, the rotation of the polygon mirror is controlled using the prediction signal.

  According to the image forming apparatus of the first aspect, when an adhering substance such as dust adheres to a specific surface of the polygon mirror and no light reception signal is output, the lack of the light reception signal is periodically detected. When an adhering substance such as dust adheres to the surface of the polygon mirror that deflects the laser beam, the adhering substance such as dust tends to adhere to the end of the surface in the rotation direction. If dust or other deposits are attached only to the edge of a specific surface of the polygon mirror, even if the received light signal is lost, the laser light output unit or optical sensor is not broken, so it is predicted instead of the received light signal. By using the signal, rotation control of the polygon mirror can be continued. Therefore, even if a deposit such as dust floating in the apparatus adheres to the reflection surface of the polygon mirror, the rotation of the polygon mirror can be controlled.

  The image system apparatus according to claim 2, further comprising: a missing counting unit that counts the number of detections of the missing detected by the missing detection unit, wherein the control unit periodically detects the missing by the determination unit. If it is determined that the number of detections is greater than or equal to a predetermined number of times in a predetermined period, the polygon mirror is stopped from rotating, and the determination unit determines that the loss is not periodically detected, If the number of detections is not greater than or equal to the predetermined number during the predetermined period, the rotation of the polygon mirror is controlled using the prediction signal at least in the missing portion.

  According to the image forming apparatus of claim 2, when the number of detected light-receiving signals is not detected periodically and the number of detected light-receiving signals is equal to or greater than a predetermined number of times, the laser beam output unit or the light Since there is a high possibility that the sensor has failed, the rotation of the polygon mirror is stopped. If the number of received light signal loss is not detected periodically, and the number of detected light signal loss is not greater than or equal to the predetermined number of times in a given period, it is highly likely that the received light signal has been accidentally lost. Is used to control the rotation of the polygon mirror. Therefore, it is possible to appropriately control whether to continue or stop the rotation of the polygon mirror.

  The image system apparatus according to claim 3, further comprising: a specifying unit that specifies a reflection surface of a polygon mirror that has been determined by the determination unit to periodically detect the loss, wherein the prediction signal output unit includes a polygon mirror The control unit can output a prediction signal in place of the light reception signal corresponding to the reflection surface, and the control unit uses the prediction signal corresponding to the reflection surface specified by the specification unit.

  According to the image forming apparatus of the third aspect, since the rotation of the polygon mirror is controlled using the prediction signal corresponding to the surface of the polygon mirror from which the light reception signal is periodically lost, it corresponds to all the surfaces of the polygon mirror. It is possible to control the rotation of the polygon mirror with higher accuracy than to control the rotation of the polygon mirror using the prediction signal.

  The image system apparatus according to claim 4 stores a first storage unit that stores a prediction interval at which a prediction signal is output for each reflection surface of the polygon mirror, and a light reception interval at which the light reception signal is output. A second storage unit; and a collation unit that collates the prediction interval stored in the first storage unit and the light reception interval stored in the second storage unit, and the prediction signal output unit includes Predicting the output timing of the received light signal and outputting a prediction signal at an equivalent output timing, the control unit corresponds to the reflecting surface specified by the specifying unit based on the information checked by the checking unit A prediction interval at which the prediction signal is output is used.

  According to the image forming apparatus of the fourth aspect, since the rotation of the polygon mirror can be controlled using the prediction signal output at the same output timing as the missing light reception signal, the rotation of the polygon mirror can be controlled with high accuracy.

  The image system apparatus according to claim 5, wherein the missing detection unit detects missing of the received light signal when the optical sensor does not receive the laser light during a period in which the optical sensor receives the laser light. The determination unit periodically detects the loss based on whether or not the laser beam deflected by a predetermined surface of the polygon mirror has never been received within a period of at least two rotations of the polygon mirror. It is judged whether it was done.

(effect)
According to the image forming apparatus of the fifth aspect of the present invention, it is determined whether or not the laser light deflected by the predetermined surface of the polygon mirror is received at least within a period in which the polygon mirror rotates twice. Since it can be determined whether or not missing is periodically detected, it can be determined at an early stage whether or not to continue the rotation control of the polygon mirror. If the laser beam deflected by the specific surface of the polygon mirror is not received at least within the period of at least two rotations of the polygon mirror, for example, it can be determined by distinguishing from the failure of the laser beam output unit or the optical sensor. Therefore, the rotation control of the polygon mirror can be appropriately continued.

  According to the present invention, the rotation of the polygon mirror can be controlled even if an adhering substance such as dust floating in the apparatus adheres to the reflection surface of the polygon mirror.

1 is a cross-sectional view showing a laser printer 1 according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the scanner unit 9 shown in FIG. FIG. 2 is a block diagram showing an electrical configuration of the laser printer 1 shown in FIG. 1. It is a figure which shows a mode that the deposit | attachment adhered to the reflective surface of the polygon mirror 13 shown in FIG. 2 is a flowchart showing the operation of the laser printer 1 shown in FIG. It is a figure which shows the mode of the detection counter of a BD signal waveform when a deposit | attachment adheres to the 2nd surface of the polygon mirror 13 shown in FIG. It is a figure which shows the area | region which memorize | stores the output space | interval of the BD signal in RAM42 shown in FIG. It is a figure which shows the area | region which memorize | stores the output interval of the prediction signal in RAM42 shown in FIG.

[Embodiment]
Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of the laser printer 1 will be briefly described, and then the details of the characteristic portions of the present invention will be described. In the following description, in FIG. 1, the right side is referred to as the “front side”, the left side is referred to as the “back side”, the back side of the paper vertical direction is referred to as the “right side”, and the front side of the paper vertical direction is the front side. The side is referred to as the “left side”. As for the vertical direction, the vertical direction in the figure is referred to as the “vertical direction” as it is.

<Overall configuration of laser printer 1>
FIG. 1 is a sectional view showing a laser printer 1 according to an embodiment of the present invention. As shown in FIG. 1, the laser printer 1 includes a feeder unit 4 for feeding a sheet 3 into a main body casing 2 as an apparatus main body, an image forming unit 5 for forming an image on the sheet 3, and the like. ing.

<Configuration of feeder unit 4>
The feeder unit 4 has a known structure, and mainly includes a paper feed tray 6, a paper pressing plate 7, and a paper transport mechanism 8. In the feeder unit 4, the sheet 3 in the sheet feeding tray 6 is moved upward by the sheet pressing plate 7 and conveyed to the image forming unit 5 by the sheet conveying mechanism 8.

<Configuration of Image Forming Unit 5>
The image forming unit 5 includes a scanner unit 9 and a process cartridge 10 that form a developer image on the paper 3, and a fixing unit 11 that thermally fixes the developer image transferred onto the paper 3 by the process cartridge 10 onto the paper 3. Etc.

  The scanner unit 9 includes a light emitting element 12 (see FIG. 2) that emits laser light, a polygon mirror 13 that rotates the laser light within a predetermined range by being rotated, an fθ lens 14, a toric lens 15, a reflecting mirror 16, 17 etc. The laser light emitted from the light emitting element 12 is irradiated onto the surface of the photoreceptor 18 through a path indicated by a two-dot chain line in the drawing. Details of the configuration of the scanner unit 9 will be described later.

  The process cartridge 10 is attached to and detached from the main casing 2 with the front cover 2 </ b> A on the front side of the main casing 2 being appropriately opened. The process cartridge 10 is mainly composed of a developing cartridge 19 and a drum unit 20.

  The developing cartridge 19 is attached to and detached from the main casing 2 together with the drum unit 20, or is attached to and detached from the drum unit 20 fixed to the main casing 2. The developing cartridge 19 mainly includes a developing roller 21, a layer thickness regulating blade 22, a supply roller 23, and a toner hopper 24.

  In the developing cartridge 19, the developer in the toner hopper 24 is stirred by the agitator 25 and then supplied to the developing roller 21 by the supply roller 23. At this time, positive friction is generated between the supply roller 23 and the developing roller 21. Charged. The developer supplied onto the developing roller 21 enters between the layer thickness regulating blade 22 and the developing roller 21 as the developing roller 21 rotates, and is further frictionally charged as a thin layer having a constant thickness. It is carried on the developing roller 21.

  The drum unit 20 mainly includes a known photoreceptor 18, a scorotron charger 26 and a transfer roller 27. In the drum unit 20, the surface of the photoconductor 18 is uniformly positively charged by a scorotron charger 26 and then exposed to laser light modulated by image data from the scanner unit 9. Is done. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed.

  Next, by the rotation of the developing roller 21, the developer carried on the developing roller 21 is supplied to the electrostatic latent image formed on the surface of the photoconductor 18, and the developer on the surface of the photoconductor 18. An image is formed. Thereafter, the sheet 3 is conveyed between the photoreceptor 18 and the transfer roller 27, whereby the developer image carried on the surface of the photoreceptor 18 is transferred onto the sheet 3.

  The fixing unit 11 has a known structure and includes a heating roller 28 and a pressing roller 29. The heating roller 28 includes a halogen heater 30 for heating the heating roller 28. In the fixing unit 11, the developer image transferred onto the paper 3 is thermally fixed while the paper 3 passes between the heating roller 28 and the pressing roller 29. The paper 3 that has passed through the fixing unit 11 is sent out onto a paper discharge tray 32 by a paper discharge roller 31.

<Configuration of scanner unit 9>
FIG. 2 is a schematic diagram showing the configuration of the scanner unit 9 shown in FIG. In FIG. 2, the right side is referred to as “front side”, the left side is referred to as “back side”, the upper side is referred to as “right side”, and the lower side is referred to as “left side”. The scanner unit 9 includes a light emitting element 12, a lens unit 35, a polygon mirror 13, an fθ lens 14, a toric lens 15 (see FIG. 1), reflecting mirrors 16 and 17 (see FIG. 1), a BD sensor 36, and the like. . The lens unit 35 includes a collimator lens and a cylindrical lens. The BD sensor 36 of this embodiment is an example of the optical sensor of the present invention.

  The light emitting element 12 is turned on or off according to a signal output from the lighting control circuit 49 (see FIG. 3). The laser beam emitted from the light emitting element 12 is applied to the polygon mirror 13 through the lens unit 35. The polygon mirror 13 is rotated at a high speed by a polygon motor 53, and the irradiated laser light is deflected by the polygon mirror 13, and the photoconductor 18 is passed through the fθ lens 14, the reflecting mirror 16, the toric lens 15, and the reflecting mirror 17. Is irradiated. The laser beam deflected by one reflecting surface of the polygon mirror 13 is scanned on one line of the photosensitive member 18. As shown in FIG. 2, the polygon mirror 13 rotates counterclockwise. The laser beam is scanned from the left side to the right side, and the BD sensor 36 and the photoconductor 18 are irradiated in this order. The light emitting element 12 and the lens part 35 of this embodiment are an example of the laser beam output part of this invention.

  FIG. 4 is a diagram showing a state in which the deposit is attached to the reflection surface of the polygon mirror 13 shown in FIG. The polygon mirror 13 is composed of six reflecting surfaces (A surface, B surface, C surface, D surface, E surface, and F surface) (see FIG. 4) and periodically deflects the laser light. In the present embodiment, the period during which the laser light is deflected by one reflecting surface of the polygon mirror 13 is one period. Therefore, in this embodiment, the polygon mirror 13 rotates once in six cycles.

  The BD sensor 36 is disposed at a position where the laser beam deflected by the polygon mirror 13 passes before scanning the photoconductor 18. The BD sensor 36 determines the lighting start timing of the light emitting element 12 that starts scanning the laser beam for each line toward the photosensitive member 18 at the time of printing. When receiving the laser beam emitted from the light emitting element 12, the BD sensor 36 outputs a BD (Beam Detect) signal to the lighting control circuit 49 (see FIG. 3). The rotation control of the polygon mirror 13 will be described later.

<Electrical Configuration of Laser Printer 1>
Next, the electrical configuration of the laser printer 1 will be described. As shown in FIG. 3, the laser printer 1 includes a CPU 40, a ROM 41, a RAM 42, a display unit 43, an operation unit 44, a feeder unit 4, an image forming unit 5, a network interface 45, and the like. FIG. 3 is a block diagram showing an electrical configuration of the laser printer 1 shown in FIG.

  The CPU 40 executes various programs stored in the ROM 41 and stores each numerical value in the RAM 42. The CPU 40 is electrically connected to the display unit 43, the operation unit 44, the feeder unit 4, the image forming unit 5, and the like. The ROM 41 stores various control programs for performing a printing operation in the laser printer 1. The RAM 42 temporarily stores numerical values set in various control programs.

  The display unit 43 includes, for example, a liquid crystal display and a lamp, and displays various setting screens and operation states. The display unit 43 also displays a warning to warn that there is an abnormality when the CPU 40 detects any abnormality of the laser printer 1. The operation unit 44 includes a plurality of buttons and switches, and various input operations such as an instruction to start printing are performed by the user. When an instruction to start printing is input from the operation unit 44 or the like, the feeder unit 4 conveys the paper 3 in the paper feed tray 6 to the image forming unit 5.

  The network interface 45 is connected to a network and enables connection with other information processing apparatuses. Data communication with an external device can be performed via the network interface 45.

  The image forming unit 5 includes a scanner unit 9 and the like. The scanner unit 9 includes a polygon mirror driving unit 48 for driving the polygon mirror 13 and a lighting control circuit 49 for controlling lighting of the light emitting element 12.

  The polygon mirror driving unit 48 includes a polygon motor 53 and a motor driver 54. The polygon motor 53 is a motor for driving the polygon mirror 13 to rotate. The motor driver 54 is connected to the polygon motor 53. The motor driver 54 inputs a digital signal to the polygon motor 53 based on a polygon mirror drive command from the CPU 40. The rotation of the polygon motor 53 is controlled based on the input digital signal. The rotation of the polygon mirror 13 is controlled by known control. The digital signal is generated so that the rotation speed of the polygon mirror 13 is predicted by the output interval of the BD signal, and the polygon mirror 13 rotates at a predetermined rotation speed. In the generation of the digital signal, when the BD signal is not output at the timing when the BD signal is output, it is assumed that the BD signal is lost, and a prediction signal described later is used instead of the BD signal.

  The lighting control circuit 49 is connected to the light emitting element 12 and the BD sensor 36. The lighting control circuit 49 controls lighting of the light emitting element 12 in accordance with the output timing of the BD signal output from the BD sensor 36. The time when a predetermined period has elapsed from the output timing of the BD signal is set as the lighting start timing of the light emitting element 12.

  When the prediction signal is used instead of the BD signal, lighting of the light emitting element 12 is controlled based on the prediction signal. The prediction signal is output at a timing immediately after the BD signal is output. As the output interval of the prediction signal, the output of the BD signal for one rotation is detected when the polygon mirror 13 is rotating at a predetermined rotation speed at the time of factory shipment, and the output interval of the detected BD signal is used. Therefore, the output interval of the prediction signal is equivalent to the output interval of the BD signal, but the output timing is different. The output interval of the prediction signal is stored in the RAM 42, and the prediction signal is output by the lighting control circuit 49. The output interval of the BD signal is slightly different for each surface (A surface, B surface, C surface, D surface, E surface, F surface) depending on the processing surface accuracy of the reflecting surface of the polygon mirror 13. In order to reduce the difference between the output timings of the BD signal and the prediction signal, in this embodiment, the reflection surface on which the prediction signal is used is specified, and the prediction signal corresponding to the specified reflection surface is used. The lighting control circuit 49 of this embodiment is an example of the prediction signal output unit of the present invention. The RAM 42 in which the output interval of the prediction signal of this embodiment is stored is an example of a first storage unit of the present invention.

  When the BD signal is missing, the lighting control circuit 49 lights the light emitting element 12 when a predetermined period has elapsed from the output timing of the prediction signal. The CPU 40 outputs a lighting signal for one line to the light emitting element 12 from the lighting start timing. Thereby, an electrostatic latent image for one line is formed on the photosensitive member 18.

<About the case where deposits such as dust adhere to the polygon mirror 13>
Next, a case where a deposit such as dust adheres to the polygon mirror 13 will be described with reference to FIG. The polygon mirror 13 on the left side of FIG. 4 is in a state where no adhering material such as dust at the time of factory shipment is attached. The polygon mirror 13 on the right side of FIG. 4 has been used for many years and is in a state in which deposits such as dust adhere to the end portions of the reflecting surfaces. The end of the reflection surface of the polygon mirror 13 rotates on the orbit of a circle indicated by a dotted line. Near the center of the reflecting surface, it rotates inside the dotted line. Therefore, if paper dust or the like of the paper 3 is floating around the polygon mirror 13, it is more likely to adhere to the end of the reflecting surface than near the center of the reflecting surface. When an adhering material such as dust containing paper dust adheres to the end of the reflecting surface, the adhering material adheres to the end of the reflecting surface as shown on the right in FIG. The BD sensor 36 cannot receive the laser beam.

  Since paper dust gradually adheres to the end of the reflective surface, the reflective surface from which the BD signal is lost gradually increases. From the state in which the output of the BD signal is normally detected, the BD signal is not suddenly lost from all the reflecting surfaces due to the influence of the deposit on the reflecting surface. When BD signals are missing from all the reflective surfaces, there is a high possibility that the light emitting element 12 or the BD sensor 36 is abnormal. When a deposit such as dust adheres to the reflective surface and the BD signal is lost, the reflective surface from which the BD signal is lost gradually increases, and thus the light emitting element 12 or the BD sensor 36 is abnormal. Can be distinguished.

<Control action>
Next, the operation of the laser printer 1 will be described with reference to FIGS. FIG. 5 is a flowchart showing the operation of the laser printer 1 shown in FIG. FIG. 6 is a diagram illustrating a waveform of a BD signal and a state of a detection counter of the BD signal when a deposit adheres to the second surface of the polygon mirror 13 illustrated in FIG. FIG. 7 is a diagram showing an area for storing the output interval of the BD signal in the RAM 42 shown in FIG. FIG. 8 is a diagram showing an area for storing the output interval of the prediction signal in the RAM 42 shown in FIG.

  When the laser printer 1 is turned on, an operation according to the flowchart shown in FIG. 5 is started. In S101, it is determined whether or not there is a print instruction. The print instruction is input by the user operating the external information processing apparatus or the operation unit 44 or the like. The laser printer 1 is in a standby state until a print instruction is input (S101: No). If it is determined that there is a print instruction (S101: Yes), rotation control of the polygon mirror 13 is performed (S102). Known rotation control is performed so that the rotation of the polygon mirror 13 is stably rotated at a predetermined speed.

  Next, in S103, it is determined whether or not a BD signal has not been detected. Whether or not the BD signal is not detected is determined, for example, based on whether or not the output of the BD signal is detected during a period in which the polygon mirror 13 rotates once after the polygon mirror 13 rotates stably at a predetermined speed. . When it is determined that the BD signal is not detected, the light emitting element 12 or the BD sensor 36 may be abnormal. Therefore, in this case, since printing cannot be continued, an error is notified and this processing is terminated (S104). If it is determined that the BD signal is not detected, the process proceeds to S201.

  In step S201, it is determined whether or not the reflecting surface of the polygon mirror 13 has adhered matter such as dust, and the output of the BD signal cannot be detected from the adhered surface. For this determination, the output of the BD signal is detected during the period in which the polygon mirror 13 rotates three times. The rotation period of the polygon mirror 13 for detecting the output of the BD signal requires at least two rotations. This is because the detection during the period in which the polygon mirror 13 is rotated once cannot distinguish between the case where the output of the BD signal is lost due to some cause and the case where the output of the BD signal from the attached surface is lost. Because. In the present embodiment, a period in which the polygon mirror 13 rotates three times is used in order to improve the determination accuracy.

  Next, in S202, it is determined whether or not the BD signal is missing. When the number of reflecting surfaces of the polygon mirror 13 is 6, the number of output BD signals detected during the period in which the polygon mirror 13 rotates 3 times is 18 times except for the number detected first. That is, if the output of the BD signal is detected 18 times during the period in which the polygon mirror 13 rotates three times, it is determined that the BD signal is not missing (S202: No), and the process proceeds to S203. S202 of this embodiment and the lighting control circuit 49 are examples of a missing detection unit of the present invention.

  In S203, since all the outputs of the BD signal can be normally detected, the data of the prediction interval for outputting the prediction signal is updated. The prediction interval data is stored in an area of the RAM 42 as shown in FIG. The output interval of the detected BD signal is updated from the prediction interval YT1 to the prediction interval YT6 in order. Since the prediction interval data at the time of shipment from the factory may be different from the current output interval of the BD signal, it is possible to output a more accurate prediction signal by updating the prediction interval data. Since the printing process of S204 can be performed using the updated prediction signal, even if the output of the BD signal is lost during the printing process, the rotation of the polygon mirror 13 can be controlled using a highly accurate prediction signal. it can. When the printing process of S204 ends, the process of this flowchart ends, the process of this flowchart starts again, and S101 is performed.

  If the number of detected BD signals output is 17 or less in S202, it is determined that the BD signal is missing (S202: Yes), and the process proceeds to S301. As shown in FIG. 6, when S201 is started, the output of the BD signal is detected during a period in which the polygon mirror 13 rotates three times. When the output of the BD signal is detected, the value of the BD signal detection counter in the RAM 42 is incremented by one. When S201 is started, the value of the BD signal detection counter is set to 0, which is an initial value. In FIG. 6, a deposit adheres to the second surface of the polygon mirror 13, and the BD sensor cannot receive the laser light from the second surface. Since no BD signal is output from the second surface, the value of the BD signal detection counter is 15. When the value of the BD signal detection counter is 17 or less, it is determined that the BD signal is missing.

  In S301, it is determined whether or not the output of the BD signal is periodically lost. If it is determined that the output of the BD signal detected in S201 is periodically lost from a specific surface (S301: Yes), it is determined that an adhering substance such as dust has adhered to the specific surface of the polygon mirror 13, and the process proceeds to S302. . When it is determined that the output of the BD signal is not lost periodically (S301: No), the process proceeds to S306.

  Whether or not the output of the BD signal is periodically lost from a specific surface is determined by measuring the output interval of the BD signal, and in the measured order, the BD output interval PT11 and the BD output interval of the RAM 42 as shown in FIG. PT21, BD output interval PT31, BD output interval PT41, BD output interval PT51, BD output interval PT61, BD output interval 12, BD output interval PT22, BD output interval PT32, BD output interval PT42, BD output interval PT52, BD output interval The data is stored in PT62, BD output interval PT13, BD output interval PT23, BD output interval PT33, BD output interval PT43, BD output interval PT53, and BD output interval PT63. However, if the output of the BD signal is not detected even after the allowable output period of the BD signal (for example, a period equal to or greater than 1.2 times the average output interval) has elapsed, a value of 0 is output because the BD signal is missing. Stored in the interval.

  As shown in FIG. 6, when the output of the BD signal from the second surface is not detected, a value of 0 is stored in the BD output interval PT21, the BD output interval PT22, and the BD output interval PT23. Therefore, when all three output interval values stored on a predetermined surface are 0, it is determined that an adhering substance such as dust has adhered to the predetermined surface. In S301, it is determined whether or not there is a surface in which the value of the output interval stored from the first surface to the sixth surface of the polygon mirror 13 is zero for all three times. The attachment surface is specified in S304 described later. S301 and the lighting control circuit 49 of this embodiment are examples of the determination unit of the present invention. The RAM 42 that stores the BD output interval PT11 to the BD output interval PT63 of the present embodiment is an example of the second storage unit of the present invention.

  Next, in S302, the output interval of the BD signal is collated with the prediction interval of the prediction signal. It is checked whether there is an output interval that coincides with the BD output interval PT11 (see FIG. 7) stored in S301 from the prediction interval YT1 to the prediction interval YT6 in order (see FIG. 8). If there is no matching output interval, it is checked whether there is an output interval that coincides with the next BD output interval PT12 in order from the prediction interval YT1 to the prediction interval YT6. This collation is performed until a matching output interval is obtained. If there is no coincident output interval, the process is performed for the output intervals of all stored BD signals. S302 of the present embodiment is an example of a matching unit of the present invention.

  Next, in S303, as a result of the collation in S302, it is determined whether or not there is an output interval in which the output interval of the BD signal matches the prediction interval of the prediction signal. If it is determined that there is no coincident output interval (S303: No), the process proceeds to the printing process of S204. In this case, the printing process is performed using a prediction signal that does not correspond to the reflection surface of the polygon mirror 13 in which the BD signal is periodically lost. If it is determined that there is a matching output interval (S303: Yes), the process proceeds to S304.

  In S304, the missing surface of the polygon mirror 13 from which the BD signal is missing is specified. That is, the attachment surface of the polygon mirror 13 to which an adhering matter such as dust is attached is specified. In S301, it is determined whether or not there is a surface where the value of the output interval stored from the first surface to the sixth surface of the polygon mirror 13 is zero for all three times, and is zero for all three times. It is specified by detecting a certain surface. As shown in FIG. 6, since the values of the BD output interval PT21, the BD output interval PT22, and the BD output interval PT23 are all 0, the second surface is specified as the missing surface (attached surface). S304 of the present embodiment is an example of the specifying unit of the present invention.

  Next, in S305, a prediction signal corresponding to the identified missing surface is output. For example, when the value of the BD output interval PT11 matches the value of the prediction interval YT4, the second surface that is a missing surface is associated with the E surface. Therefore, a prediction signal output based on the prediction interval YT5 is used instead of using the BD signal of the second surface. When there are a plurality of missing surfaces, prediction signals are output using prediction intervals corresponding to the respective surfaces. In S204, the printing process is performed using the BD signal on the surface where the BD signal is not lost, and using the prediction signal corresponding to the surface on the surface where the BD signal is missing.

  If it is determined in S301 that the output of the BD signal is not periodically lost, it is determined in S306 whether the number of missing BD signals is a predetermined number (for example, 3 times) or more. This is performed to distinguish whether the BD signal is accidentally lost once or twice for some reason, or whether the BD signal is lost more than a predetermined number of times due to an abnormality in the BD sensor 36 or the like. If the BD signal is missing more than a predetermined number of times (S306: Yes), there is a high possibility that the BD signal has been lost more than a predetermined number of times due to an abnormality in the BD sensor 36, etc., so an error is notified (S307), Exit. If the BD signal is not lost more than the predetermined number of times (S306: No), it is highly likely that the BD signal is lost once or twice for some reason. Therefore, the process proceeds to S204 and the printing process is performed. When a BD signal is lost during the printing process, a stored prediction signal is output. The number of missing BD signals can be determined by counting the number of 0 stored in the output interval in S301. The number in which 0 is stored in the values from the BD signal output interval PT11 to the BD signal output interval PT63 is counted and stored in the missing counter of the RAM. The S306 and the missing counter in the present embodiment are examples of the missing counting unit of the present invention. S301 to S307 of this embodiment, CPU40, and the polygon mirror drive part 48 are examples of the control part of this invention.

[Modification]
The present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the present invention. An example is described below.

  In the present embodiment, the present invention may be applied not only to a laser printer but also to other image forming apparatuses such as a copying machine and a multifunction machine.

  The output interval that matches the BD output interval 11 stored in S301 is collated in order from the prediction interval YT1 to the prediction interval YT6, but the output interval closest to the BD output interval 11 from the prediction interval YT1 to the prediction interval YT6 is checked. May be selected and collated. When there are a plurality of closest output intervals, collation is performed to select the output interval closest to the next BD output interval 21. This collation is performed in the order of the output intervals of the stored BD signals until the nearest output interval becomes one. When the nearest output interval becomes one, information on the nearest output interval is used to associate a prediction interval instead of the output interval of the surface where the BD signal is missing. In step S204, printing processing is performed by outputting a prediction signal instead of the BD signal of the missing surface using the associated prediction interval.

DESCRIPTION OF SYMBOLS 1 Laser printer 3 Paper 5 Image formation part 9 Scanner unit 10 Process cartridge 12 Light emitting element 13 Polygon mirror 36 BD sensor 40 CPU
41 ROM
42 RAM
49 Lighting control circuit

Claims (5)

A laser beam output unit for outputting a laser beam;
A polygon mirror for deflecting the laser beam;
An optical sensor that outputs a light reception signal when receiving the laser beam deflected by the polygon mirror;
A control unit for controlling the rotation of the polygon mirror using the light reception signal;
A prediction signal output unit that outputs a prediction signal instead of the light reception signal;
A missing detector for detecting missing of the received light signal;
A determination unit for determining whether or not the loss is periodically detected, and
The control unit controls rotation of the polygon mirror using the prediction signal at least in the missing part when the judging unit judges that the missing is periodically detected. Forming equipment. The image forming apparatus according to claim 1.
A missing counting unit that counts the number of detections of the missing detected by the missing detection unit;
The controller is
When the determination unit determines that the lack is not periodically detected and the number of detections is equal to or greater than a predetermined number in a predetermined period, the rotation of the polygon mirror is stopped,
When the determination unit determines that the missing is not periodically detected and the number of detections is not greater than or equal to the predetermined number in the predetermined period, at least in the missing part, the polygon is determined using the prediction signal. An image forming apparatus that controls rotation of a mirror. The image forming apparatus according to claim 1, wherein:
A specifying unit that specifies a reflection surface of a polygon mirror that is determined by the determination unit to detect the loss periodically;
The prediction signal output unit can output a prediction signal instead of the light reception signal corresponding to the reflection surface of the polygon mirror,
The image forming apparatus, wherein the control unit uses the prediction signal corresponding to the reflection surface specified by the specifying unit. The image forming apparatus according to claim 3.
A first storage unit that stores a prediction interval at which a prediction signal is output for each reflection surface of the polygon mirror;
A second storage unit that stores a light reception interval at which the light reception signal is output;
A collation unit that collates the prediction interval stored in the first storage unit and the light reception interval stored in the second storage unit,
The prediction signal output unit predicts the output timing of the light reception signal and outputs a prediction signal at an equivalent output timing,
The image forming apparatus according to claim 1, wherein the control unit uses a prediction interval at which the prediction signal corresponding to the reflecting surface specified by the specifying unit is output based on the information checked by the checking unit. The image forming apparatus according to any one of claims 1 to 4, wherein:
The missing detection unit detects missing of the received light signal when the optical sensor does not receive the laser light during a period of receiving the laser light,
The determination unit periodically detects the loss based on whether or not the laser beam deflected by a predetermined surface of the polygon mirror has never been received within a period of at least two rotations of the polygon mirror. An image forming apparatus characterized by determining whether or not it has been performed.

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