JP2007253386A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can move to the next action and start image formation at an early stage as soon as a necessary adjustment ends. <P>SOLUTION: When a monitor voltage exceeds a BD sensor threshold to enable feedback control based on a first BD signal, a rotating speed of a polygon mirror is immediately adjusted by the feedback control. When the monitor voltage exceeds a starting power passing value MIN to enable a bias adjustment process to start, the bias adjustment process is started immediately. Moreover, in a state with a bias adjustment completion flag raised and also a polygon motor Lock signal generated, when the monitor voltage enters a gap between a printing power passing value MAX and a printing power passing value MIN, processing of a printing DATA signal is started immediately. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus capable of performing an image forming operation using a semiconductor laser that generates laser light and a scanning unit that scans and exposes a photosensitive member with the laser light.

  2. Description of the Related Art Conventionally, a semiconductor laser that generates a laser beam corresponding to an energization current and a scanning unit that scans and exposes a photosensitive member with the laser beam generated by the semiconductor laser are provided, and an image is obtained using the semiconductor laser and the scanning unit. An image forming apparatus capable of performing a forming operation is considered. In this type of image forming apparatus, it is necessary to start the image forming operation after performing various adjustments such as adjusting the light amount of the laser light from the semiconductor laser to a light amount suitable for the image forming operation.

Therefore, it is proposed that the amount of light from a laser diode as an example of a semiconductor laser be detected by, for example, a photodiode, and controlled using a differential amplifier or sample hold circuit so that the monitor current flowing through the photodiode becomes a predetermined value. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 11-123845

  However, in Patent Document 1, an adjustment time required for the light amount adjustment is set in advance, and it is checked whether the light amount adjustment is actually completed after the adjustment time has elapsed. For this reason, even when the light amount adjustment by the circuit is completed at an early stage, the image forming apparatus must stand by for a preset adjustment time without shifting to the image forming operation. Further, in Patent Document 1, it is described that when the light amount adjustment is completed within the set adjustment time, the adjustment time is updated to a shorter time. In this case, the image forming apparatus is also updated. You must wait for a later adjustment time. In view of the above, an object of the present invention is to provide an image forming apparatus capable of proceeding to the next operation as soon as necessary adjustments are completed and starting image formation at an early stage.

  In order to achieve the above object, the present invention comprises a semiconductor laser that generates a laser beam corresponding to an energization current, and a scanning unit that scans and exposes a photosensitive member with the laser beam generated by the semiconductor laser. An image forming apparatus capable of performing an image forming operation using a laser and the scanning unit, wherein the laser beam is detected at a scanning origin by the scanning unit and a light amount detecting unit that detects a light amount of the laser beam from the semiconductor laser. The origin detecting means for detecting the semiconductor laser, the energization current to the semiconductor laser is gradually increased, the origin detecting means detects the laser light, and the light quantity detecting means detects the light quantity suitable for the image forming operation. In this case, a first control unit that permits the image forming operation is provided.

  The image forming apparatus of the present invention configured as described above can execute an image forming operation using a semiconductor laser and a scanning unit, and the light amount detecting unit detects the light amount of the laser light from the semiconductor laser. The origin detection means detects the laser beam at the scanning origin by the scanning means. The first control means gradually increases the energization current to the semiconductor laser, the origin detection means detects the laser light, and the light quantity detection means detects a light quantity suitable for the image forming operation. If so, the image forming operation is permitted.

  For this reason, in the present invention, when the origin detection unit detects the laser beam and the light amount detection unit detects the light amount suitable for the image forming operation and the image forming operation becomes possible, the image forming operation is immediately performed. It is possible to allow. Therefore, in the present invention, image formation can be started at an early stage. However, in the present invention, it is not always necessary to start the image forming operation immediately after the origin detecting unit detects the laser beam and the light amount detecting unit detects a light amount suitable for the image forming operation. You may leave.

  Further, the first control unit may execute error processing when the light source detection unit detects a light amount suitable for the image forming operation and the origin detection unit does not detect the laser beam. Good. In this case, there is a further effect that error processing can be executed for an abnormality in the origin detecting means or the scanning means.

  Further, the first control unit performs error processing when the light amount detection unit does not detect a light amount suitable for the image forming operation even after a predetermined time has elapsed after the origin detection unit detects the laser light. May be executed. In this case, there is a further effect that error processing can be executed for the abnormality of the light amount detection means or the semiconductor laser.

  According to another aspect of the present invention, there is provided a semiconductor laser that generates a laser beam corresponding to an energized current, and a scanning unit that scans and exposes a photosensitive member with the laser beam generated by the semiconductor laser. An image forming apparatus capable of performing an image forming operation using a laser and the scanning unit, wherein an origin detecting unit for detecting the laser beam at a scanning origin by the scanning unit, and an energization current to the semiconductor laser gradually. And a second control means for starting adjustment of the scanning speed of the scanning means based on a detection signal from the origin detecting means when the origin detecting means detects the laser beam. It may be a feature.

  The image forming apparatus of the present invention configured as described above can perform an image forming operation using a semiconductor laser and a scanning unit, and the origin detection unit detects the laser beam at the scanning origin by the scanning unit. . The second control means gradually increases the energization current to the semiconductor laser, and when the origin detection means detects the laser beam, the scanning of the scanning means is performed based on the detection signal from the origin detection means. Start speed adjustment.

  For this reason, in the present invention, when the origin detection means detects the laser beam and the scanning speed can be adjusted based on the detected laser beam, the adjustment of the scanning speed based on the detection signal from the origin detection means can be started immediately. Is possible. Therefore, in the present invention, image formation can be started at an early stage. However, in the present invention, it is not always necessary to start the adjustment of the scanning speed immediately after the origin detecting means detects the laser beam, and a slight pause may be used.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing a schematic configuration of a laser printer 1 as an image forming apparatus to which the present invention is applied. In the following description, the right side in FIG.

(Whole structure of laser printer)
The laser printer 1 is a direct transfer tandem color laser printer, and includes a substantially box-shaped main casing 2 as shown in FIG. A front cover 3 that can be opened and closed is provided on the front surface of the main casing 2. By opening the front cover 3, the process unit 25 can be drawn forward from the main casing 2. Further, on the upper surface of the main casing 2, a paper discharge tray 5 on which paper 4 as a recording medium after image formation is stacked is formed.

  A paper feed tray 7 on which paper 4 for forming an image is loaded is attached to the lower portion of the main body casing 2 so as to be drawn forward. In the paper feed tray 7, there is provided a paper pressing plate 9 that can be tilted to lift the front end side of the paper 4 by the bias of the spring 8. In addition, a pickup roller 10 and a separation pad 11 that presses against the pickup roller 10 by biasing a spring (not shown) are provided at a position above the front end of the paper feed tray 7. Further, a pair of paper feed rollers 12 is provided obliquely in front of the pickup roller 10, and a pair of registration rollers 13 is provided thereabove.

  When the uppermost sheet 4 of the sheet feeding tray 7 is pressed toward the pickup roller 10 by the sheet pressing plate 9 and is sandwiched between the pickup roller 10 and the separation pad 11 by the rotation of the pickup roller 10, 1 is reached. Separated by sheet. Then, the paper 4 sent out between the pickup roller 10 and the separation pad 11 is sent to the registration roller 13 by the paper feed roller 12. The registration roller 13 feeds the paper 4 onto the rear belt unit 15 at a predetermined timing.

  The belt unit 15 is attachable to and detachable from the main casing 2 and includes a conveyor belt 18 that is horizontally installed between a pair of belt support rollers 16 and 17 that are spaced apart from each other in the front-rear direction. The conveyor belt 18 is an endless belt made of a resin material such as polycarbonate, and is circulated and moved counterclockwise in FIG. 1 when the rear belt support roller 17 is driven to rotate, and is placed on the upper surface thereof. The paper 4 is conveyed backward. Inside the conveying belt 18, four transfer rollers 19 arranged to face each photosensitive drum 31 (corresponding to a photosensitive member) included in an image forming unit 26 described later are provided at regular intervals in the front-rear direction. The conveyance belt 18 is sandwiched between the photosensitive drum 31 and the corresponding transfer roller 19. At the time of transfer, a transfer bias is applied between the transfer roller 19 and the photosensitive drum 31.

  A cleaning roller 21 is provided below the belt unit 15 to remove toner, paper dust, and the like attached to the conveyance belt 18. The cleaning roller 21 has a configuration in which a foam material made of silicon is provided around a metal shaft member, and the conveyance belt 18 is sandwiched between the cleaning roller 21 and a metal backup roller 22 provided in the belt unit 15. Opposite. A predetermined bias is applied between the cleaning roller 21 and the backup roller 22, whereby the toner and the like on the conveyor belt 18 are electrically attracted to the cleaning roller 21 side. Further, the cleaning roller 21 is in contact with a metal recovery roller 23 that removes toner or the like adhering to the surface, and the recovery roller 23 is a blade for scraping off the toner or the like adhering to the surface. 24 abuts.

  A scanner unit 27 as a laser scanning device is provided at the upper part in the main body casing 2, a process unit 25 is provided below the scanner unit 27, and the belt unit 15 is disposed below the process unit 25. Yes.

  The scanner unit 27 irradiates the surface of the corresponding photosensitive drum 31 with laser light L for each color based on predetermined image data at high speed. The configuration of the scanner unit 27 will be described in detail later.

  The process unit 25 includes four image forming units 26 corresponding to each color of black (K), cyan (C), magenta (M), and yellow (Y), and these image forming units 26 are arranged in the front and rear. Is arranged in. In the present embodiment, the image forming units 26 are arranged in the order of black, cyan, magenta, and yellow from the front side of the laser printer 1. Each image forming unit 26 includes a photosensitive drum 31 as an image carrier, a scorotron charger 32, a developing cartridge 34 as a developing device, and the like. Further, the process unit 25 includes a frame-like frame 29 having four cartridge mounting units 30 arranged in the front-rear direction. Each cartridge mounting part 30 is opened up and down, and each developing cartridge 34 can be attached / detached inside thereof. The frame 29 holds the photosensitive drum 31 of each image forming unit 26 at the lower end position of each cartridge mounting portion 30, and further holds the scorotron charger 32 adjacent to the photosensitive drum 31. Yes.

  The photoconductor drum 31 includes a grounded metal drum body, and the surface layer thereof is covered with a positively chargeable photoconductive layer made of polycarbonate or the like. The scorotron charger 32 is disposed opposite to the photosensitive drum 31 at a predetermined interval so as not to come into contact with the photosensitive drum 31 in the diagonally upper rear side of the photosensitive drum 31. The scorotron charger 32 uniformly charges the surface of the photosensitive drum 31 to positive polarity by generating corona discharge from a charging wire (not shown) such as tungsten.

  The developing cartridge 34 has a substantially box shape, and a toner storage chamber 38 is provided in an upper portion thereof, and a supply roller 39, a developing roller 40, and a layer thickness regulating blade 41 are provided below the developing cartridge 34. Each toner storage chamber 38 stores, as a developer, positively chargeable nonmagnetic one-component toner of each color of black, cyan, magenta, or yellow. Each toner storage chamber 38 is provided with an agitator 42 for stirring the toner.

  The supply roller 39 is configured by coating a metal roller shaft with a conductive foam material, and the developing roller 40 is configured by coating the metal roller shaft with a conductive rubber material. Yes. The toner discharged from the toner storage chamber 38 is supplied to the developing roller 40 by the rotation of the supply roller 39 and is positively frictionally charged between the supply roller 39 and the developing roller 40. Further, the toner supplied onto the developing roller 40 enters between the layer thickness regulating blade 41 and the developing roller 40 with the rotation of the developing roller 40, where it is further sufficiently frictionally charged to have a constant thickness. It is carried on the developing roller 40 as a thin layer.

  The surface of the photosensitive drum 31 is first uniformly charged positively by the scorotron charger 32 when rotating. Thereafter, exposure is performed by high-speed scanning of laser light from the scanner unit 27, and an electrostatic latent image corresponding to an image to be formed on the paper 4 is formed.

  Next, when the developing roller 40 rotates and the positively charged toner carried on the developing roller 40 comes into contact with and faces the photosensitive drum 31, a static image formed on the surface of the photosensitive drum 31 is formed. The electric latent image is supplied. As a result, the electrostatic latent image on the photosensitive drum 31 is visualized, and a toner image with toner attached only to the exposed portion is carried on the surface of the photosensitive drum 31.

  Thereafter, the toner image carried on the surface of each photosensitive drum 31 is transferred while the paper 4 conveyed by the conveying belt 18 passes through each transfer position between the photosensitive drum 31 and the transfer roller 19. The images are sequentially transferred onto the paper 4 by a negative transfer bias applied to the roller 19. The sheet 4 having the toner image transferred thereon is then conveyed to the fixing device 43.

  The fixing device 43 is disposed behind the conveyance belt 18 in the main body casing 2. The fixing device 43 includes a heating roller 44 that is rotationally driven with a heat source such as a halogen lamp, and a pressure roller 45 that is disposed below the heating roller 44 so as to face the heating roller 44 and is driven to rotate. It has. The fixing device 43 fixes the toner image on the paper 4 by heating the paper 4 carrying the four color toner images while nipping and conveying the paper 4 by the heating roller 44 and the pressure roller 45. Then, the sheet 4 on which the toner image has been thermally fixed is further conveyed by a conveyance roller 46 disposed obliquely above and behind the fixing device 43, and is discharged by the discharge roller 47 provided at the upper part of the main body casing 2. The paper is discharged onto the paper tray 5.

(Configuration of scanner unit)
FIG. 2 is a simplified diagram for explaining the configuration of the scanner unit 27. Of these, the lower diagram is a left-side cross section of the scanner unit 27, and the upper diagram (each reflection mirror is omitted) is a diagram of the inside of the scanner unit 27 as viewed from above. In the drawing, the right side is the front side of the laser printer 1, and the paper 4 is conveyed by the belt unit 15 from the right to the left of the paper. That is, the left direction of the paper is the conveyance direction of the paper 4 and the sub-scanning direction on the photosensitive drum 31. In the upper diagram, the laser beam Lk and the laser beam Ly are developed without being folded by the reflection mirror, and an optical path optically equivalent to the lower diagram is shown.

  As shown in the figure, the scanner unit 27 includes a box-shaped resin housing 50, and has, for example, a six-sided polygon mirror 51 (corresponding to a scanning means) driven by a polygon motor 49 at the approximate center in the inside. Is provided so as to be rotatable (driven to rotate counterclockwise in the figure). The housing 50 is provided with four laser light sources as semiconductor lasers, more specifically, laser diodes LDk, LDc, LDm, and LDy near the right side of the polygon mirror 51.

  The laser diode LDk is directed to one deflecting surface of the polygon mirror 51 located slightly obliquely from the upper position, and is arranged so as to emit the laser light Lk modulated based on the black printing DATA signal through the cylindrical lens 52. ing. The laser beam Lk deflected by the polygon mirror 51 is guided to the front side of the laser printer 1, passes through the first scanning lens 53 (for example, fθ lens), is folded back by the reflecting mirror 54, and is further folded downward by the reflecting mirror 55. Then, the light passes through the second scanning lens 56k (for example, a toric lens) and is irradiated onto the surface of the photosensitive drum 31k of the black image forming unit 26k. The laser beam Lk is scanned at high speed from the left to the right (upward in the drawing in the upper drawing: hereinafter referred to as the first scanning direction) on the surface of the photosensitive drum 31k by the rotation of the polygon mirror 51.

  The laser diode LDc is directed to one deflection surface (the same deflection surface as the laser diode LDk) of the polygon mirror 51 located obliquely above from the lower position of the laser diode LDk, and is modulated based on the cyan print DATA signal. Is emitted through a cylindrical lens 52. The laser beam Lc is deflected by the same deflection surface as the laser beam Lk, guided to the front side of the laser printer 1, transmitted through the first scanning lens 53, folded back by the reflection mirrors 57 and 58, and further reflected by the reflection mirror 59. It is folded downward and transmitted through a second scanning lens 56c (for example, a toric lens) to be irradiated on the surface of the photosensitive drum 31c of the cyan image forming unit 26c. The laser beam Lc is scanned at high speed along the first scanning direction on the surface of the photosensitive drum 31 c by the rotation of the polygon mirror 51.

  The laser diode LDm is arranged side by side behind the laser diode LDk, and is one deflection surface of the polygon mirror 51 located slightly diagonally from the upper position (deflection surface adjacent to the deflection surface to which the laser diodes LDk and LDc are directed). The laser beam Lm that is modulated based on the magenta print DATA signal is emitted through the cylindrical lens 60. The laser beam Lm deflected by the polygon mirror 51 is guided to the rear surface side of the laser printer 1 (substantially opposite to the laser beams Lk and Lc), passes through the first scanning lens 61 (for example, fθ lens), and is reflected by the reflecting mirrors 62 and 63. Then, it is folded back forward by the reflecting mirror 64, transmitted through the second scanning lens 56m (for example, toric lens), and irradiated onto the surface of the photosensitive drum 31m of the magenta image forming unit 26m. The laser beam Lm is rotated from the right to the left on the surface of the photosensitive drum 31m by the rotation of the polygon mirror 51 (the lower direction in the drawing in the upper drawing: the direction opposite to the laser beams Lk and Lc: hereinafter referred to as the second scanning direction). ).

  The laser diode LDy is directed to one deflection surface (the same deflection surface as the laser diode LDm) of the polygon mirror 51 located obliquely upward from the lower position of the laser diode LDm, and is modulated based on the yellow print DATA signal. Are arranged so as to be emitted through the cylindrical lens 60. The laser beam Ly deflected by the polygon mirror 51 is guided to the rear surface side of the laser printer 1, passes through the first scanning lens 61, is folded back by the reflecting mirror 65, and is further folded downward by the reflecting mirror 66 to be folded downward. The light passes through 56y (for example, a toric lens) and is irradiated onto the surface of the photosensitive drum 31y of the yellow image forming unit 26y. The laser beam Ly is scanned at high speed along the second scanning direction on the surface of the photosensitive drum 31y by the rotation of the polygon mirror 51. The first scanning lenses 53 and 61, the second scanning lens 56, and the reflection mirrors 54, 55, 57 to 59, and 62 to 66 are supported and fixed in the housing 50 of the scanner unit 27.

  The housing 50 is provided with a first BD (Beam Detect) sensor 67 (an example of an origin detecting means) at the left end of the front inner wall surface, and a second BD sensor 68 at the left end of the rear inner wall surface. Yes. The first BD sensor 67 can receive the laser beam Lk immediately before reaching the surface of the photosensitive drum 31k, and based on the first light reception timing, not only the laser beam Lk but also the laser beams Lc and Lm. , Ly, the scanning start timing (writing start timing in the main scanning direction) to each photosensitive drum 31 is determined. The second BD sensor 68 can receive the laser beam Ly immediately after being scanned on the surface of the photosensitive drum 31y.

(Configuration of laser printer control system)
FIG. 3 is a block diagram showing the configuration of the control system of the polygon motor 49 and the laser diodes LDk, LDc, LDm, and LDy. Since each laser diode LDk, LDc, LDm, LDy is connected to the ASIC 80 as an example of the first control means and the second control means via the same circuit, FIG. 3 relates to the laser diode LDk. Only the circuit is shown and the others are omitted.

  As shown in FIG. 3, the laser diode LDk is housed in a laser diode unit 69 together with a photodiode PD (an example of a light amount detecting means) for detecting the light amount generated by the laser diode LDk.

  The anode of the photodiode PD is connected to the A / D input port of the ASIC 80 and grounded via the variable resistor VR. The cathode of the photodiode PD is connected to a 5V power source together with the anode of the laser diode LDk. For this reason, the anode voltage of the photodiode PD (hereinafter also referred to as a monitor voltage) changes in accordance with the amount of light of the laser diode LDk. Further, an LD power control unit 72 is connected to the cathode of the laser diode LDk via a high-speed modulation circuit 71.

  The LD power control unit 72 is set by a PWM / A conversion unit 73 that converts the PWM signal input from the ASIC 80 into an analog voltage, and a voltage output from the PWM / A conversion unit 73 and a reference voltage setting unit 74. A comparison circuit error amplifier 75 that amplifies the difference from the reference voltage with a predetermined gain, and an LD drive current control circuit 76 that controls the drive current to the laser diode LDk according to the output of the comparison circuit error amplifier 75. Yes. The high-speed modulation circuit 71 switches the short-circuit / insulation between the laser diode LDk and the LD power control unit 72 according to the black print DATA signal input from the ASIC 80.

  A bias control unit 77 is connected to the cathode of the laser diode LDk in parallel with the high-speed modulation circuit 71 and the LD power control unit 72. The bias control unit 77 converts a PWM signal input from the ASIC 80 into an analog voltage, and a bias current to the laser diode LDk according to the voltage output from the PWM / A conversion unit 78. And an LD bias current control circuit 79 for controlling.

  The ASIC 80 inputs a PWM signal corresponding to the monitor voltage input as an analog signal (ANALOG signal) to the LD power control unit 72 when the print DATA signal is ON (when the high-speed modulation circuit 71 is in a short circuit state). By this control, the drive current of the laser diode LDk is controlled so that the amount of light when the laser diode LDk is turned on becomes a value corresponding to the reference voltage.

  Further, the ASIC 80 gradually increases the current supplied to the laser diode LDk through the bias control unit 77 when the laser diode LDk is turned off (when the high-speed modulation circuit 71 is in an insulating state), and the laser diode LDk An energization current that does not generate Lk (oscillation light) (hereinafter referred to as a bias current) is detected. Then, when the laser diode LDk is turned off, the detected bias current is energized through the bias controller 77 to improve the response of the laser diode LDk to the print DATA signal.

  Further, a first BD signal that is a detection signal of the first BD sensor 67 is input to the ASIC 80. A polygon motor 49 is connected to the ASIC 80 via a drive circuit (not shown).

  Here, for example, the bias current detection process (hereinafter referred to as a bias adjustment step) cannot be executed while the amount of light is very small immediately after energization of the laser diode LDk. The rotation speed of the polygon motor 49 is preferably feedback-controlled based on the detection timing of the first BD signal, but this control cannot be executed while the amount of light is very small immediately after the laser diode LDk is energized. Therefore, in the present embodiment, the execution timing of various controls is set as follows.

(Control system operation)
FIG. 4 is a time chart showing the execution timing of various controls in the ASIC 80. As shown in FIG. 4, when the laser printer LDk-LDy is allowed to be driven by other known control when the laser printer 1 is started, the ASIC 80 drives the laser diodes LDk-LDy via the LD power control unit 72. Increase the current gradually. Then, as shown in FIG. 4, the monitor voltage also gradually increases.

  On the other hand, when the polygon motor drive permission is generated by other known control when the laser printer 1 is started, the ASIC 80 starts driving the polygon motor 49. However, the first BD signal is not input immediately after the start-up when the light amount of the laser diode LDk is small. Therefore, immediately after the laser printer 1 is activated, the ASIC 80 feedback-controls the speed of the polygon motor 49 based on an FG (Frequency Generation) signal generated by the polygon motor 49 itself.

  Thereafter, when the monitor voltage rises and the laser beam Lk reaches the BD sensor threshold value that can be detected by the first BD sensor 67, the first BD signal is input to the ASIC 80. Then, as shown in FIG. 4, the ASIC 80 sets a BD detection flag and switches the control of the polygon motor 49 to the feedback control based on the first BD signal. When the rotation speed of the polygon motor 49 is stabilized at the desired speed by this feedback control, the ASIC 80 generates a polygon motor lock signal.

  The monitor voltage is set with a start power pass value MAX and a start power pass value MIN as upper and lower limits of the monitor voltage at which an image forming operation can be started. Therefore, when the monitor signal further rises and exceeds the startup power pass value MIN, the ASIC 80 sets the startup power reach flag and starts the bias adjustment process as part of the image forming operation. Even during the bias adjustment step, the laser diode LDk is turned on near the detection timing of the first BD signal, and the monitor voltage is detected at that time.

  When the bias current is detected and the bias adjustment process is completed, the ASIC 80 sets a bias adjustment completion flag and sets a print power pass value MAX and a print power pass value MIN as thresholds for new monitor voltages. This is an upper limit value and a lower limit value for determining whether or not there is an abnormality during image formation, and the width of both is a width that allows the start of the image forming operation (starting power pass value MAX and start power pass value MIN). And narrower).

  Then, the ASIC 80 sets the monitor voltage of each laser diode LDk to LDy to the print power pass value MAX while the bias adjustment completion flag is set for each laser diode LDk to LDy and the polygon motor Lock signal is generated. And the print power pass value MIN, the print power O.D. K. Set a flag. This printing power O.D. K. While the flag is set, the print DATA signal of each color input to the laser printer 1 is input to the high-speed modulation circuit 71 via the ASIC 80, and an image corresponding to the print DATA signal can be formed on the paper 4. .

  Thus, in this embodiment, when the monitor voltage exceeds the BD sensor threshold value and feedback control based on the first BD signal becomes possible, the rotational speed of the polygon motor 49 is immediately adjusted by the feedback control. . In addition, when the monitor voltage exceeds the start power pass value MIN and the bias adjustment process can be started, the bias adjustment process is started immediately. Further, when the bias adjustment completion flag is set and the monitor voltage of each laser diode LDk to LDy is between the print power pass value MAX and the print power pass value MIN while the polygon motor lock signal is generated. Immediately, the printing DATA signal is inputted to the high-speed modulation circuit 71. Therefore, in this embodiment, image formation can be started very early. Note that the above-described processes do not necessarily have to be started immediately, and may be delayed. Also in this case, image formation can be started at an early stage as compared with the technique described in Patent Document 1 and the like described above.

  The ASIC 80 includes a CPU, a ROM, and a RAM, and executes the following abnormality notification process based on the software program during the control. FIG. 5 is a flowchart showing the abnormality notification process.

  As shown in FIG. 5, when the process is started, it is first determined in S1 (S represents a step: the same applies hereinafter) whether or not the BD detection flag is set. Since the BD detection flag is not raised immediately after startup (S1: N), the process proceeds to S2, and it is determined whether the startup power arrival flag of the laser diode LDk is set. Immediately after the activation, the activation power reaching flag is not raised (S2: N), and the process proceeds to S1 described above.

  In this way, the ASIC 80 waits until either the BD detection flag or the above-mentioned activation power reach flag is set while repeating the processing of S1 and S2. If the activation power arrival flag is set before the BD detection flag is set (S1: N, S2: Y), it is considered that a rotation failure has occurred in the polygon mirror 51 or an abnormality has occurred in the first BD sensor 67. It is done. Therefore, in this case, the abnormality of the polygon mirror 51 or the first BD sensor 67 is notified through a display panel or a communication interface (not shown), and the process ends. In this case, the subsequent image forming operation is stopped.

  When the BD detection flag is raised while the processes of S1 and S2 are repeated (S1: Y), the process proceeds to S5, and it is determined whether or not all the activation power arrival flags for each color are raised. If all the start power arrival flags are not set (S5: N), whether or not a predetermined time set to a time sufficient for the monitor voltage to exceed the start power pass value MIN has passed in S6. To be judged. If the predetermined time has not elapsed (S6: N), the process again proceeds to S5, and the processes of S5 and S6 are repeated.

  If a predetermined time has elapsed without the activation power reaching flag being set (S5: N, S6: Y), any one of the laser diodes LDk to LDy or a photodiode paired with the laser diodes LDk to LDy It is conceivable that an abnormality occurred in PD. Therefore, in this case, the abnormality of the laser diode LD or the photodiode PD is notified through the display panel or the communication interface, and the process ends. Also in this case, the subsequent image forming operation is stopped.

  On the other hand, if all of the activation power arrival flags for each color are set (S5: Y) before the predetermined time elapses (S5: Y), the processing is terminated as it is, and the image as described above is assumed to be normal. A forming operation is performed. Thus, in this embodiment, error processing (abnormality notification) for the polygon mirror 51, the first BD sensor 67, the laser diode LD, and the photodiode PD can also be executed.

(Other embodiments)
In addition, this invention is not limited to the said embodiment at all, It can implement with a various form in the range which does not deviate from the summary of this invention. For example, in the above embodiment, the various flag processes shown in FIG. 4 are executed by hardware in the ASIC 80, but may all be executed by software.

1 is a side sectional view showing a schematic configuration of a laser printer to which the present invention is applied. It is a simplified diagram for explaining the configuration of the scanner unit of the laser printer. It is a block diagram showing the structure of the control system of the scanner unit. It is a time chart showing the execution timing of various controls in the control system. It is a flowchart showing the abnormality alerting | reporting process in the control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 25 ... Process part 26 ... Image forming unit 27 ... Scanner unit 31 ... Photosensitive drum 34 ... Developing cartridge 49 ... Polygon motor 51 ... Polygon mirror 67 ... First BD sensor 71 ... High-speed modulation circuit 72 ... LD power control part 77 ... Bias controller LD ... Laser diode PD ... Photo diode

Claims (4)

A semiconductor laser that generates laser light in accordance with an energization current;
Scanning means for scanning and exposing the photosensitive member with laser light generated by the semiconductor laser;
An image forming apparatus capable of performing an image forming operation using the semiconductor laser and the scanning unit,
A light amount detecting means for detecting a light amount of laser light from the semiconductor laser;
Origin detecting means for detecting the laser beam at the scanning origin by the scanning means;
When the energization current to the semiconductor laser is gradually increased, the origin detection unit detects the laser light, and the light amount detection unit detects a light amount suitable for the image forming operation, the image forming operation is performed. First control means to permit;
An image forming apparatus comprising:   The first control unit performs error processing when the light source detection unit detects a light amount suitable for the image forming operation and the origin detection unit does not detect the laser beam. The image forming apparatus according to claim 1.   The first control unit executes error processing when the light amount detection unit does not detect a light amount suitable for the image forming operation even after a predetermined time has elapsed after the origin detection unit detects the laser light. The image forming apparatus according to claim 1. A semiconductor laser that generates laser light in accordance with an energization current;
Scanning means for scanning and exposing the photosensitive member with laser light generated by the semiconductor laser;
An image forming apparatus capable of performing an image forming operation using the semiconductor laser and the scanning unit,
Origin detecting means for detecting the laser beam at the scanning origin by the scanning means;
When the energization current to the semiconductor laser is gradually increased and the origin detection means detects the laser beam, second adjustment is started to adjust the scanning speed of the scanning means based on the detection signal from the origin detection means. Control means;
An image forming apparatus comprising:

Images