JP4985563B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, the number of rotations of a drive motor for rotationally driving a polygon mirror is detected by an FG sensor, and the drive motor is rotated at a predetermined number of rotations (hereinafter referred to as “FG rotation”) based on the detection result. Internal control and external control for detecting the timing of the main scanning of the light beam on the photosensitive member by the SOS sensor and rotating the drive motor at a predetermined rotation (hereinafter referred to as “SOS rotation”) based on the detection result. When switching from FG rotation to SOS rotation, the SOS signal is detected to prevent the SOS signal from being missed even when the drive motor rotates faster. A light source lighting control method has been proposed in which the timing (SOS search lighting section) at which the light beam is incident is quickly taken. That is, a technique for switching from a mode in which lighting for APC is performed at a normal timing (Run APC) to a mode in which an SOS search lighting section is quickly taken (Middle APC) is disclosed.

  For example, in a conventional image recording apparatus, switching from FG rotation to SOS rotation is performed in order to align the phases of SOS signals. In other image recording apparatuses, the SOS rotation uses the SOS rotation because the pitch variation is better than the FG rotation. Furthermore, the setting of the image writing timing is simplified by utilizing the fact that the phases of the SOS signals are aligned.

  When switching from FG rotation to SOS rotation, if switching to SOS rotation immediately after the input of the SOS signal, the time from the immediately preceding FG signal to the next input SOS signal becomes longer than the reference clock, and the drive motor rotates. Although it becomes faster, the normal SOS search lighting section is taken early, so that the SOS signal is prevented from being missed even when the rotation of the drive motor becomes faster.

  As described above, in the lighting control method of the light source disclosed in Patent Document 1, the start of the SOS search lighting section is changed to prevent the SOS signal from being missed when switching to SOS rotation, but the start of APC is changed. Depending on the timing to perform, SOS search lighting is performed during APC.

  FIG. 8 shows a case of switching from Run APC to Middle APC. The LD that executes APC is switched at the rising edge of CKAPC that executes APC when APCST = “L” (Low level), which is an APC start signal. Switching between both modes is performed by switching the registers of RAPC_EN_AP and RAPC_EN_NP. Here, when the register is rewritten during the APC at the timing of Run APC when switching from the Run APC in FIG. 5A to the Middle APC in FIG. 5B, as shown in FIG. The APC signal is output until the APC of all the beams is completed, but the SOS search lighting is performed at the timing after the change. As a result, the APC and the SOS search are performed simultaneously from t1 when the SOS search starts to t2 when the APC ends.

  FIG. 9 shows a case of switching from Middle APC to Run APC. Here, when switching from the Middle APC in FIG. 5B to the Run APC in FIG. 5A, when the register is rewritten at the timing of Run APC during the Middle APC, as shown in FIG. APC starts, and SOS search lighting is performed at the timing after the change. As a result, APC and SOS search are simultaneously performed from t3 when APC starts until t4 when APC ends.

  The original operation of APC is to adjust the amount of light for each laser diode (hereinafter referred to as “LD”). In the SOS search lighting, in the other image recording apparatuses described above, 7 LDs are lighted simultaneously to obtain the SOS signal. When APC and SOS search lighting are performed at the same time, control is performed so that the light amount of the seven LDs of SOS search lighting is equal to the light amount of one LD. As a result, there is a possibility that the amount of light of the LD subjected to APC is reduced and the SOS signal cannot be obtained.

Switching between Run APC and Middle APC is performed by setting the register as described above. However, the time for setting the register is performed regardless of the SOS period, and it is not known where the SOS period is switched.
JP 2001-174728 A

  An object of the present invention is to provide an image forming apparatus that switches a timing at which a light beam for detecting a start timing of main scanning is incident without causing a malfunction of light quantity control.

  In order to solve the above-mentioned object, an image forming apparatus according to claim 1, wherein the light beam output from the light source is deflected by a rotary polygon mirror to expose and scan the image carrier, and the image light is output from the light source. A light amount control means for performing light amount control of the light beam; a scanning start signal output means for receiving the light beam output from the light source; and outputting a scanning start signal to the exposure means based on the light reception result; and the scanning A scanning period control unit that controls a period during which the light beam to be incident on the start signal output unit is output; and a period in which the light beam is output by the scanning period control unit. Lighting control means for controlling to stop the light amount control.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the first rotational speed detecting means for detecting the rotational speed of the rotary polygon mirror and the deflected light beam are received and The second rotation number detecting means for detecting the number of rotations of the rotary polygon mirror, and the rotation based on one of the detection results of the first rotation number detection means and the second rotation number detection means. Rotation control means for controlling the rotation speed of the polygon mirror to be switched, and the scanning period control means responds to switching of the rotation speed of the rotation polygon mirror based on a detection result used for control of the rotation control means. The output period of the light beam is controlled to be changed.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus further comprises a light amount control start signal transmitting means for transmitting a light amount control start signal of the light beam output from the light source. The light quantity control means performs the light quantity control when receiving the start signal emitted from the light quantity control start signal transmission means, and the lighting control means transmits the start signal by the light quantity control start signal transmission means at least once. Control to stop.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the lighting control unit outputs a scanning start signal to the exposure unit by at least the scanning start signal output unit. Control is performed so that the light amount control by the light amount control means is stopped until the next scanning start signal is output.

  6. The image forming apparatus according to claim 5, wherein the light beam output from the light source is deflected by a rotating polygon mirror to expose and scan the image carrier, and the light amount for controlling the light amount of the light beam output from the light source. A control means, a scanning start signal output means for receiving a light beam outputted from the light source, and outputting a scanning start signal to the exposure means based on the light receiving result; and for entering the scanning start signal output means A scanning period control unit that controls a period during which the light beam is output; and when the scanning period control unit changes the period during which the light beam is output, at least the scanning after the light amount control unit starts the light amount control. The light beam is output after a time from when the start signal output means outputs a scanning start signal to the exposure means until the next scanning start signal is output. And includes a lighting control means for controlled so, the.

  According to the first to fourth aspects of the invention, it is possible to temporarily stop the light amount control and prevent a malfunction of the light amount control when switching the timing at which the light beam for detecting the start timing of the main scanning is incident. it can.

  According to the fifth aspect of the present invention, it is possible to prevent malfunction of the light amount control by delaying the light amount control timing when switching the timing at which the light beam for detecting the main scanning start timing is switched.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an image forming apparatus according to the present embodiment.

  As shown in FIG. 2, the image forming apparatus 10 is provided with a plurality of drum-shaped photoreceptors 14 along the longitudinal direction of the transfer belt 12. Since the image forming apparatus 10 according to the present embodiment uses a color image as a target image, the photoconductors 14 corresponding to four colors of cyan (C), magenta (M), yellow (Y), and black (K) are provided. It is arranged. For members arranged corresponding to each color, such as a photoconductor and an optical scanning device, C, M, Y, K alphabets are added to the end of the reference only when they are described separately. I will explain.

  Around the photosensitive member 14, a charger, a developing device, a first transfer device, a cleaner, and the like (not shown) are arranged, and optical scanning that irradiates the photosensitive member 14 with a light beam modulated based on the target image. A device 16 (details will be described later) is arranged. When the light beam is irradiated from the optical scanning device 16 onto the photoconductor 14 uniformly charged by the charger, a latent image corresponding to the target image is formed on the surface of the photoconductor 14.

  The latent image formed on the surface of the photoconductor 14 is developed with toner for each color by a developing device disposed around the photoconductor 14. That is, a toner image is formed on the surface of the photoreceptor 14. Note that cyan, magenta, yellow, and black toners corresponding to the respective photoreceptors 14C, 14M, 14Y, and 14K are at issue in the developing unit.

  The toner image formed on the surface of the photoreceptor 14 is transferred to the transfer belt 12 by the first transfer device. The transfer belt 12 can be rotated in a predetermined direction (the direction of arrow D shown in FIG. 1) by the conveying rollers 18A and 18B and one roller 20A constituting the second transfer device 20. To the transfer belt 12, the toner images formed on the surfaces of the photoreceptors 14C, 14M, 14Y, and 14K are sequentially transferred. In other words, cyan, magenta, yellow, and black toner images are transferred onto the transfer belt 12 in an overlapping manner. In this embodiment, the toner image in which the four color toner images are transferred in a superimposed manner is referred to as a final toner image.

  The toner image remaining on the surface of the photoconductor 14 at the end of transfer of the toner image to the transfer belt 12 is removed by a cleaner (not shown), and the photoconductor 14 is discharged by a charge removal lamp (not shown).

  A second transfer device 20 is disposed at a position facing the position where the photoconductor 14 is disposed with respect to the transfer belt 12. The second transfer device 20 is composed of two rollers 20A and 20B facing each other. The second transfer device 20 transfers the final toner image transferred to the transfer belt 12 to a paper 22 that is discharged from a paper tray (not shown) and conveyed in the direction of arrow E shown in FIG. The paper 22 on which the final toner image has been transferred is fixed by a fixing device (not shown). As a result, a desired image is formed on the paper 22.

  Further, image position detection sensors 24A, 24B, and 24C are disposed along the width direction of the transfer belt 12 on the downstream side in the transport direction of the transfer belt 12 with respect to the position where the photoconductor 14 is disposed. An area along the width direction of the transfer belt 12 corresponds to an image scannable area on the photoreceptor 14. The image position detection sensors 24A, 24B, and 24C detect the position of the final toner image transferred to the transfer belt 12.

  FIG. 2 shows a detailed configuration of the optical scanning device 16. As shown in FIG. 2, the optical scanning device 16 includes an LD 100 as a light source, and a polygon mirror 116 that reflects the light beam emitted from the LD 100 and irradiates the corresponding photosensitive member 14 with the light beam. ing. The LD 100 may have a single light emitting point. In this embodiment, a monolithic LD having a plurality of (hereinafter, two) light emitting points and one photodiode (PD) for detecting the amount of output light is used.

  The LD 100 is controlled by a lighting control unit 202 (details will be described later), that is, emission of a light beam. A collimator lens 102 and a slit 104 are sequentially arranged on the downstream side in the traveling direction of the light beam emitted from the LD 100. The light beam emitted from the LD 100 is converted from a diffused ray to a parallel ray by the collimator lens 102 and shaped by the slit 104. The light beam that has passed through the slit 104 sequentially passes through an expander lens 106, a reflecting mirror 108, a cylinder lens 110, a reflecting mirror 112, an fθ lens 114 including a first lens 114A and a second lens 114B, and then a polygon mirror. 116 is incident.

  The polygon mirror 116 is formed in a regular polygonal shape (a regular dodecagon in this embodiment) having a plurality of reflecting surfaces 116A provided on the side surface, and the incident light beam converges on the reflecting surface 116A. Further, the polygon mirror 116 is pivotally attached to a polygon motor 150 (see FIG. 3: described later) whose rotation is controlled at a predetermined speed. The rotation of the polygon motor 150 causes the polygon mirror 116 to rotate in a direction indicated by an arrow F around the rotation shaft 118. Rotates at speed.

  The incident angle of the light beam on each reflecting surface 116 </ b> A is continuously changed and deflected by rotating the polygon mirror 116 by the rotation of the polygon motor 150. Accordingly, the photosensitive member 14 is irradiated with a light beam by scanning in the axial direction of the photosensitive member 14.

  The beam width in the scanning direction of the light beam incident on the polygon mirror 116 is sufficiently larger than the size of the reflecting surface 116A (so-called overfilled type), and the polygon mirror 116 cuts off the incident light beam. to scan.

  The light beam reflected by the polygon mirror 116 passes through the fθ lens 114 again, is reflected by the cylinder mirror 120, and is guided to the photoreceptor 14. The light beam reflected by the polygon mirror 116 is converted by the fθ lens 114 to a constant scanning speed when the photosensitive member 14 is irradiated with the light beam, and on the circumferential surface of the photosensitive member 14 in the main scanning direction. Imaged. Further, the cylinder mirror 120 forms an image on the peripheral surface of the photoconductor 14 also in the sub-scanning direction.

  A reflection mirror 122 is disposed between the fθ lens 114 and the cylinder mirror 120 and on the path of the light beam that travels to the scanning start position of the photoconductor 14. The light beam traveling to the scanning start position of the photoreceptor 14 is reflected by the reflection mirror 122.

  An SOS sensor 124 including a light detection sensor such as a photodiode is disposed in the direction in which the light beam is reflected by the reflection mirror 122 and at a position substantially equal to the photoreceptor 14 with respect to the reflection mirror 122. Each time the light beam scans the photosensitive member 14 in the axial direction, the light beam traveling to the scanning start position is incident on the SOS sensor 124.

  That is, the SOS sensor 124 can detect the scanning start timing when the photosensitive member 14 is scanned with the light beam. The SOS sensor 124 outputs an SOS signal indicating the detected scanning start timing. This SOS signal is used for drive control of the polygon motor 150 and the like. Hereinafter, drive control of the polygon motor 150 will be described. FIG. 3 shows a control block diagram of the polygon motor 150.

  The polygon motor 150 is provided with an FG sensor 152 for detecting the rotation speed of the polygon motor, and a pulse signal (FG signal) synchronized with the rotation speed of the polygon motor 150 is generated. The FG signal generated by the FG sensor 152 is input to the selector 154. The selector 154 also receives an SOS signal detected from the SOS sensor 124.

  The selector 154 is connected to the PLL control circuit 156 and selectively sends an FG signal or an SOS signal to the PLL control circuit as a comparison clock. The selection of the FG signal / SOS signal by the selector 154 is performed based on a selection instruction signal FGSEL input from the correction control unit 200 via the clock changing unit 158 according to an instruction from a CPU (not shown). That is, the selector 154 selects the FG signal when the selection instruction signal FGSEL is at H (High) level, and selects the SOS signal when it is at L (Low) level.

  Specifically, the selector 154 selects an FG signal as a comparison clock and sends it to the PLL control circuit 156 before an image forming process execution instruction is input, that is, before the image forming apparatus enters an image forming state. To be controlled. When an effective instruction for image forming processing is input, that is, when the image forming apparatus shifts to an image forming state, the SOS signal is selected as a comparison clock and is controlled to be sent to the PLL control circuit 156.

  The PLL control circuit 156 is connected to the reference clock generation unit 160 and receives the reference clock generated by the reference clock generation unit 160. The PLL control circuit 156 outputs a speed control signal for controlling the driving speed of the polygon motor 150 so that the input reference clock and the comparison clock are in a phase locked state with a predetermined phase difference.

  The speed control signal output from the PLL control circuit 156 is input to the motor drive circuit 162 that controls the driving of the polygon motor 150. The motor drive circuit 162 controls the drive of the polygon motor 150 based on the input speed control signal. Thereby, the polygon motor 150 is always controlled at an appropriate rotational speed and an appropriate phase.

  That is, when the image forming apparatus is not in an image forming state, the polygon mirror 116 is moved at a constant speed by PLL control by comparing the reference clock supplied from the reference clock generator 160 and the FG signal from the FG sensor 152. Rotate accurately. Further, when the image forming apparatus is in an image forming state, the polygon mirror 116 is accurately controlled at a constant speed by PLL control by comparing the reference clock supplied from the reference clock generator 160 and the SOS signal from the SOS sensor 124. Rotate well.

  Here, the reference clock generation unit 160 outputs the clock signal of the predetermined frequency f0 generated by the source oscillation clock 164 to the PLL control circuit 156 as the reference clock signal via the clock changing unit 158. The source oscillation clock 164 is provided for each polygon motor 150 (common to each color), and the clock changing means 158 is provided for each polygon motor 150 (each color).

  Each clock changing unit 158 can temporarily change the frequency of the reference clock from f0 to f1 as necessary. Note that the frequency change of the reference clock by the clock changing unit 158 is performed based on a change instruction signal from the correction control unit 200.

  When the frequency f1 of the reference clock is changed, the PLL control circuit 156 controls the rotation speed of the polygon motor 150 based on the changed frequency of the reference clock. After that, when the frequency of the reference clock is returned to the original frequency f0, the polygon motor 150 returns to the original rotational speed, but the rotational phase, that is, the surface position of the polygon mirror is the same as when the reference frequency is not changed. Will shift. In this way, by controlling the surface position (phase) of the polygon mirror of each color with the reference clock generated from the common source oscillation clock 164, the transfer of the polygon mirror of each color can be relatively controlled.

  FIG. 4 shows a detailed configuration of the lighting control unit 202 that controls lighting of the LD 100 provided in the optical scanning device 16. 4, the lighting control unit 202 includes a FIFO (first in first out) 20, a screen generator (SG) 232, an image timing generation unit 234, a pre-SOS lighting timing generation unit 236, an APC timing generation unit 238, and an APC. An output control unit 250 and the like are included. The lighting control unit 202 is connected to a CPU that controls various processes in the image forming apparatus 10 via a bus (not shown), and various setting data set by the CPU and the SOS acquired by the SOS sensor 124. A signal is input.

  In the FIFO 230, image data output from an image processing unit (not shown) is temporarily stored in order to control the output timing. The image timing generation unit 234 outputs an LS signal serving as a read permission signal corresponding to the position in the main scanning direction of the image set by the CPU to the FIFO 230. Thereby, the FIFO 230 outputs the image data to the SG 232 when the LS signal is input.

  The image clock is input from the image clock control circuit 210 to SG232. The image clock control circuit 210 generates an image clock in synchronization with the SOS signal from the SOS 124. In SG232, multi-bit image data is converted into a modulation signal that matches the characteristics of the LD 100, and is output to the OR circuit 240 in accordance with the image clock.

  The pre-SOS lighting timing generation unit 236 generates a pre-SOS lighting signal in accordance with the pre-SOS lighting timing data set by the CPU. That is, the pre-SOS lighting signal is output after the time set by the pre-SOS lighting timing data from the SOS signal. The generated pre-SOS lighting signal is output to the OR circuit 240.

  The APC timing generation unit 238 generates an APC signal for executing light amount control of the light beam. The generated APC signal is output to the OR circuit 240 via the APC output control unit 250. The APC output control unit 250 controls on / off of the output of the APC signal in accordance with the APC mode switching data set by the CPU. That is, the APC output control unit 250 sets whether or not to output the APC signal output from the APC timing generation unit 238 to the LD driving unit 242 and the OR circuit 240.

  The OR circuit 240 outputs LD lighting data to the LD driving unit 242 when any of image data, a pre-SOS lighting signal, and an APC signal is input. The LD driving unit 242 controls the lighting of the LD 100 based on the LD lighting data.

  That is, when image data is input, the LD 100 is turned on to scan the image with respect to the photoreceptor 14. When the pre-SOS lighting signal is input, the LD 100 is forcibly lit immediately before the SOS signal output timing. Further, when the APC signal is input, the LD 100 is forcibly lit to execute the light amount control of the light beam. When an LD having a plurality of light emitting points is used, the lighting control unit shown in FIG. 4 may be provided for each light emitting point.

  The optical scanning device 16 includes the SOS sensor 124, the light amount detection unit 254, and the feedback circuit 256. The SOS sensor 124 guides the light beam with a reflection mirror, and acquires an SOS signal. A light quantity detector (MPD: Monitoring Photo Diode) 254 converts the incident light beam into a current signal, further converts it into a voltage, and outputs it to the feedback circuit 256. The feedback circuit 256 compares the voltage value output from the light amount detection unit 254 with the reference voltage value acquired from the outside, and outputs the comparison result to the LD drive unit 242.

  Next, the flow of the operation of the image forming apparatus 10 according to the present embodiment will be described. The image forming apparatus 10 detects an SOS failure signal when the image forming process is not being performed. However, when an execution instruction for the image forming process is input, the image forming apparatus 10 can execute the image processing. In order to shift to a new state, that is, an image forming state, the CPU executes a control routine shown in FIG.

  In step 300, the lighting control unit 202 stops FAIL detection. Specifically, detection of the SOS_FAIL signal and the nM_READY signal is stopped. The SOS_FAIL signal is a signal indicating the failure of SOS. The nM_READY signal is a signal for checking whether or not the polygon motor 150 is rotating properly, and is output by the PLL control circuit 156.

  In step 302, the APC output control unit 250 inactivates the APCST_N signal. This is set by an FPGA (Field Programmable Gate Array) register. As a result, the APCST_N signal output from the APC timing generation unit 238 is not output to the LD driving unit 242 and the OR circuit 240.

  In step 304, the process waits for 1 ms until the APCST_N signal is set in the FPGA register.

  In step 306, the APC timing generation unit 238 changes the setting of the RARC_EN_AP signal in the register to advance the timing at which the light amount control starts. In addition, the pre-SOS lighting timing generation unit 238 changes the setting of the RARC_EN_NP in the register to advance the timing at which the SOS search is started and to increase the SOS search time. As a result, the setting of the lighting control unit 202 becomes a Middle APC state that is a transitional state until the transition to the image forming state. These settings are made in the VECKY register (ASIC: Application Specific Integrated Circuit).

  In step 308, 1 ms is waited until the VECKY register is set.

  In step 310, the APC timing generation unit 238 activates the APCST_N signal. This is set by the FPGA register. As a result, the APCST_N signal output by the APC timing generation unit 238 is output to the LD driving unit 242 and the OR circuit 240.

  In step 312, the comparison clock used for rotation control of the polygon motor 150 is switched from the FG signal to the SOS signal. This is performed based on the FGSEL signal output from the clock changing unit 158. The FGSEL signal is a selection instruction signal for selecting whether the signal to be compared by the PLL control circuit 156 as a reference clock is the FG signal or the SOS signal. When FGSEL = “L”, the PLL control circuit 156 has the SOS signal. Compare the signal with the reference clock.

  In step 314, the process waits until the rotational fluctuation of the polygon motor 150 resulting from the switching of the comparison clock from the FG signal to the SOS signal converges. In this embodiment, the time required for the rotation fluctuation of the polygon motor to converge is set to 1 s (seconds).

  In step 316, the APC timing generation unit 238 makes the APCST_N signal inactive. This is set by the FPGA register. As a result, the APCST_N signal output from the APC timing generation unit 238 is not output to the LD driving unit 242 and the OR circuit 240.

  In step 318, 1 ms is waited until the APCST_N signal is set in the FPGA register.

  In step 320, the APC timing generation unit 238 changes the setting of the RARC_EN_AP signal in the register to delay the timing at which the light amount control starts. In addition, the pre-SOS lighting timing generation unit 238 changes the setting of the RARC_EN_NP signal in the register to advance the timing at which the SOS search starts and shorten the SOS search time. As a result, the setting of the lighting control unit 202 becomes the Run APC state, which is a state during normal image processing. These settings are made with the VECKY register.

  In step 322, 1 ms is waited until the VECKY register is set.

  In step 324, the APC timing generation unit 238 activates the APCST_N signal. This is set by the FPGA register. As a result, the APCST_N signal output by the APC timing generation unit 238 is output to the LD driving unit 242 and the OR circuit 240.

  In step 326, the lighting control unit 202 starts the FAIL detection stopped in step 300, and the activation operation for starting image processing is completed.

  FIG. 6 shows a timing chart of the present embodiment. As shown in FIG. 6, while the APC lighting control signal is stopped, the SOS search lighting timing is changed to switch the APC mode.

  The image forming process 10 according to the present embodiment operates as described above, thereby preventing the APC and the SOS search from being performed at the same time when the APC mode is switched between Run APC and Middle APC.

  FIG. 7 is a timing chart showing that the APC and the SOS search are not performed simultaneously according to this embodiment. FIG. 7A shows the Run APC state, FIG. 7B shows the state when switching to Middle APC, and FIG. 7C shows the state switched to Middle APC.

  In the Run APC state of FIG. 7A, APC is executed when the APCST signal, which is an APC start enable signal, is “L”.

  In FIG. 7B, output of the APCST signal is stopped. When switching from Run APC to Middle APC, execution of APC is stopped by setting the APCST signal to “H”. As a result, even if the SOS search is started, the APC and the SOS search lighting will not be batted.

  As described above, according to the present embodiment, when the APC mode is changed, the APC is temporarily stopped so that the APC and the SOS search are not performed simultaneously. As a method of temporarily stopping APC, a method of stopping the output of the APCST signal, which is an APC start enable signal, at least once, or at least the time from the SOS search to the next SOS search (SOS cycle) A method of stopping APC is conceivable.

  As another embodiment, when the APC mode is changed, the APC start timing and the SOS search lighting start timing are shifted at least by the SOS period, so that the APC and the SOS search are performed. May be performed at the same time.

  FIG. 8 is a timing chart showing that the APC and the SOS search are not performed simultaneously according to another embodiment. 8A is the Run APC state, FIG. 8B is the state where the APC start timing is changed, FIG. 8C is the state where the SOS search lighting start timing is changed, and FIG. 8D is switched to Middle APC. Indicates the state.

  In the Run APC state of FIG. 8A, as in the case of FIG. 7A, APC is executed when the APCST signal, which is an APC start enable signal, is “L”.

  In FIG. 8B, when the APCST signal is switched, the RAPC_EN_AP signal is first changed so that only the APC start timing is changed first, and the SOS search lighting is turned on at the same timing.

  In FIG. 8C, the RAPC_EN_NP signal is changed so that the SOS search lighting is delayed by the SOS cycle. That is, when the APC start timing is changed, the SOS search search lighting start timing is not changed, but is changed after the time corresponding to the SOS cycle has elapsed. As a result, even if the SOS search is started, the APC and the SOS search lighting will not be batted.

  In addition, this invention is not limited to the above-mentioned embodiment, It is applicable also to what changed the design within the range described in the claim.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a detailed block diagram of an optical scanning device. It is a control block diagram of a polygon motor. It is a block diagram of a lighting control part. It is a flowchart which shows the control routine performed when transfering to an image formation state. It is a timing chart which shows stopping APC when switching the mode of APC. It is a timing chart (the 1) which shows that APC and SOS search do not batting. It is a timing chart (the 2) which shows that APC and SOS search do not batting. It is a timing chart which shows the problem of switching from Run APC to Middle APC in the prior art. It is a timing chart which shows the problem of switching from Middle APC to Run APC in the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Photosensitive body (image holding body)
16 Optical scanning device 100 Laser diode 116 Polygon mirror 150 Polygon motor 202 Lighting control unit 236 Pre-SOS lighting timing generation unit 238 APC timing generation unit 250 APC output control unit

Claims (5)

Exposure means for exposing and scanning the image carrier by deflecting the light beam output from the light source by a rotating polygon mirror;
A light amount control means for performing light amount control of a light beam output from the light source;
A scanning start signal output means for receiving a light beam output from the light source and outputting a scanning start signal to the exposure means based on the light reception result;
Scanning period control means for controlling a period during which the light beam to be incident on the scanning start signal output means is output;
A lighting control means for controlling to stop the light quantity control by the light quantity control means when the period for outputting the light beam is changed by the scanning period control means;
An image forming apparatus. First rotational speed detection means for detecting the rotational speed of the rotary polygon mirror;
Second rotational speed detection means for receiving the deflected light beam and detecting the rotational speed of the rotary polygon mirror;
Rotation control means for controlling to switch the rotation speed of the rotary polygon mirror based on one of the detection results of the first rotation speed detection means and the second rotation speed detection means; Prepared,
The said scanning period control means controls to change the output period of the said light beam according to switching of the rotation speed of the said rotary polygon mirror based on the detection result used for control of the said rotation control means. Image forming apparatus. A light amount control start signal transmitting means for transmitting a light amount control start signal of the light beam output from the light source;
The light quantity control means performs the light quantity control when receiving a start signal issued by the light quantity control start signal transmission means,
The image forming apparatus according to claim 1, wherein the lighting control unit performs control so as to stop the transmission of the start signal by the light amount control start signal transmission unit at least once. The lighting control unit stops the light amount control by the light amount control unit at least for a period of time from when the scanning start signal output unit outputs a scanning start signal to the exposure unit and when the next scanning start signal is output. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled as follows. Exposure means for exposing and scanning the image carrier by deflecting the light beam output from the light source by a rotating polygon mirror;
A light amount control means for performing light amount control of a light beam output from the light source;
A scanning start signal output means for receiving a light beam output from the light source and outputting a scanning start signal to the exposure means based on the light reception result;
A scanning period control means for controlling a period for outputting a light beam to be incident on the scanning start signal output means;
When changing the period during which the light beam is output by the scanning period control unit, after the light amount control unit starts the light amount control, at least the scanning start signal output unit outputs a scanning start signal to the exposure unit. Lighting control means for controlling to output the light beam after the time until the next scanning start signal is output;
An image forming apparatus.

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