JP2020091364A - Image-forming device - Google Patents

Abstract

To return a scanner motor to a stable state immediately by controlling setting of a mask signal when abnormality occurs in a rotational reference signal.SOLUTION: An optical scanner 2 has a scanner motor 16 for driving a rotary polygon mirror, an image control part 5 has a mask signal generation part 43 for generating a mask signal of a rotational reference signal, an abnormal cycle detection part 46 for outputting a mask enabling signal for detecting a cycle of a rotational reference signal and enabling masking of the rotational reference signal, or a mask prohibition signal for prohibiting masking, a mask circuit 41 for outputting a signal obtained by masking a rotational reference signal by a mask signal in the mask enabling signal and for outputting a signal obtained by preventing masking of a rotational reference signal in the mask prohibition signal, and a motor control part 30 for controlling a speed of the scanner motor on the basis of a signal outputted from the mask circuit 41. The abnormal cycle detection part 46 outputs a mask enabling signal when a cycle of a rotational reference signal is within a predetermined range, and outputs a mask prohibition signal when a cycle of a rotational reference signal deviates from a predetermined range.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus, and more particularly to controlling a scanner motor of an optical scanning device.

Conventionally, in an optical scanning device included in an image forming apparatus, a method is known in which a light beam emitted from a semiconductor laser is deflected by a rotating polygon mirror, and is irradiated onto a photosensitive drum via an f-θ lens to perform exposure. .. In such an optical scanning device, it is necessary to stably control the rotation of the scanner motor that drives the rotary polygon mirror. Therefore, the beam detector detects the light beam deflected by the rotary polygon mirror and outputs a beam detection signal. The optical scanning device generates a rotation reference signal of the scanner motor using the beam detection signal, and controls the scanner motor to rotate at a constant speed based on the generated rotation reference signal. On the other hand, when the light beam does not reach the beam detector, the beam detection signal is not output, so that the rotation reference signal of the scanner motor is not generated and the rotation control of the scanner motor cannot be stably performed.

Therefore, for example, Patent Document 1 proposes the following method. That is, when the beam detection signal cannot be detected, the automatic return control unit controls the laser control unit to forcibly cause the light source that is the target of the automatic return operation to continuously emit light. Then, when the automatic return control unit acquires the main-scan count value of the 1-line scan, the automatic return control unit determines the lighting position of the light source for detecting the beam detection signal based on the acquired main-scan count value of the 1-line scan. Reset.

Patent No. 5358904

In the above-mentioned conventional technique, when the beam detection signal which is the basis of the rotation reference signal cannot be detected, the semiconductor laser which is the light source is forcibly made to continuously emit light to obtain the beam detection signal. However, it is not possible to deal with an output failure such as a signal omission of the beam detection signal due to a change in the power source of the beam detector. Further, when an erroneous edge occurs in the beam detection signal due to noise mixed in the transmission path between the optical scanning device and the image control unit that controls the optical scanning device, the image control unit causes the erroneous edge in one cycle of the beam detection signal. It may be erroneously detected as the start of. For example, noise may be removed by masking the beam detection signal with a mask signal in order to remove noise, but noise cannot always be removed in all cases. Further, the position of the mask signal may be changed by falsely detecting noise as an edge, and as a result, the beam detection signal may be masked, resulting in signal omission. Therefore, the cycle of the rotation reference signal generated based on the beam detection signal in which a signal dropout or a false edge occurs changes. Then, the acceleration/deceleration control of the rotation of the scanner motor is performed according to the difference between the period of the rotation reference signal and the predetermined period, and the stable control of the scanner motor for smooth image formation is impaired. Therefore, when the abnormality of the rotation reference signal occurs, the problem is how to quickly return the rotation of the scanner motor to stable rotation.

The present invention has been made under such a situation, and an object thereof is to control the setting of a mask signal when an abnormality of a rotation reference signal occurs, and to quickly return the scanner motor to a stable state. ..

In order to solve the problems described above, the present invention has the following configurations.

(1) An image forming apparatus including an optical scanning device that exposes a photosensitive member and a control unit that controls the optical scanning device, wherein the optical scanning device exposes the photosensitive member with a light beam emitted from a light source. In order to do so, a motor for driving the rotary polygon mirror for deflecting the light beam, and a rotation control unit for controlling the rotation of the motor are provided, and the control unit is generated according to the rotation of the motor. A signal generation unit that generates a mask signal for removing noise in the rotation reference signal, and detects the cycle of the rotation reference signal, and according to the detected cycle of the rotation reference signal, the rotation reference signal based on the mask signal. A mask permission signal for permitting masking, or a masking prohibition signal for inhibiting masking of the rotation reference signal by the masking signal, and when the masking permission signal is output from the cycle detecting unit, A signal generated by masking the rotation reference signal with the mask signal generated by the signal generation unit, and when the masking inhibition signal is output from the cycle detection unit, the rotation reference signal is generated by the signal generation unit. A signal output unit that outputs a signal that is not masked by the mask signal generated by the unit, and controls the rotation control unit of the optical scanning device based on the signal output from the signal output unit. And a motor control unit for accelerating or decelerating the motor, wherein the cycle detection unit outputs the mask permission signal to rotate the rotation when the cycle of the rotation reference signal is within a predetermined range. An image forming apparatus, which outputs the mask prohibition signal when the cycle of the reference signal is out of a predetermined range.

According to the present invention, it is possible to control the setting of the mask signal when the abnormality of the rotation reference signal occurs, and quickly return the scanner motor to the stable state.

Schematic sectional view showing the configuration of the image forming apparatus of Examples 1 to 4. Schematic diagram of a main part for explaining the configuration of the optical scanning device of Examples 1 to 4. Block diagram showing the configuration of the optical scanning device and the image control unit of Examples 1 to 4. Block diagram showing the configuration of the motor control unit 30 of the LS control unit of the first to fourth embodiments FIG. 6 is a diagram illustrating the operation of the mask control unit according to the first to fourth embodiments. Timing chart for explaining a method of generating a motor control signal according to the first to fourth embodiments Timing chart for explaining the motor control when the rotation reference signal of the first embodiment has a short cycle Timing chart for explaining the motor control when the rotation reference signal of the first embodiment has a long cycle Timing chart for explaining the motor control by the method in which the mask signal of Example 1 follows the cycle of the rotation reference signal. Block diagram showing the configuration of a mask control unit of the first embodiment Timing chart for explaining the mask signal generation method of the first embodiment Block diagram showing a configuration of a mask control unit of the second embodiment Timing chart for explaining the mask signal generation method of the second embodiment Block diagram showing the configuration of a mask control unit of the third embodiment FIG. 6 is a diagram illustrating a relationship between a rotation reference signal and a motor lock signal according to the third embodiment. Timing chart for explaining the mask signal generation method of the third embodiment Block diagram illustrating the configuration of the image control unit of the fourth embodiment Flowchart showing a control sequence for detecting an abnormality in the scanner motor according to the fourth embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of image forming apparatus]
FIG. 1 is a sectional view showing the overall configuration of an electrophotographic image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 includes an optical scanning device 2Y, 2M, 2C, 2K, an image control unit 5, an image reading unit 500, an image forming unit 506 including photosensitive drums 25Y, 25M, 25C, and 25K, a fixing unit 504, and a sheet feeding unit. /Consists of the transport unit 505. The image reading unit 500 illuminates a document placed on a document table to optically read the image of the document and converts the read image into image data (electrical signal). The image control unit 5, which is a control unit, receives the image data from the image reading unit 500, converts the received image data into an image signal, and transmits the image signal to the optical scanning device 2 (2Y, 2M, 2C, 2K). The image controller 5 has a CPU 503 (see FIG. 3) described later, and controls light emission of the optical scanning devices 2Y, 2M, 2C, 2K and rotation control of a scanner motor 16 (see FIG. 2) described later. The subscripts Y, M, C, and K in FIG. 1 indicate that the configurations correspond to yellow (Y), magenta (M), cyan (C), and black (K), respectively. In the following, the suffix of the reference numeral will be omitted unless it refers to a specific photosensitive drum or the like. Further, an operation unit 140 having an input unit for inputting data and a display unit for displaying information is provided on the upper portion of the image forming apparatus 1.

The image forming unit 506 has four image forming stations P (PY, PM, PC, PK). The four image forming stations P have the same configuration, and along the rotation direction (clockwise direction) of the endless intermediate transfer belt 511, yellow (Y), magenta (M), cyan (C), and black (K). Are arranged in order. Each of the image forming stations P has a photosensitive drum 25 that is a photoconductor that rotates in the arrow direction (counterclockwise direction), and around the photosensitive drum 25, along the rotation direction (counterclockwise direction), A charging device 3, a developing device 4, and a cleaning device 7 are arranged.

The charger 3 uniformly charges the surface of the rotating photosensitive drum 25 with the same potential. The optical scanning device 2 emits a light beam modulated according to an image signal to form an electrostatic latent image on the surface of the photosensitive drum 25. The developing device 4 develops the electrostatic latent image formed on the photosensitive drum 25 (photosensitive member) by attaching toner (developer) of each color to the toner and developing the electrostatic latent image. By the primary transfer member 6, the toner images on the photosensitive drum 25 are sequentially superimposed and transferred onto the intermediate transfer belt 511 to form a color image. The cleaning device 7 collects the toner remaining on the photosensitive drum 25 without being transferred to the intermediate transfer belt 511.

The sheet S, which is a recording medium, is conveyed from the paper feed cassette 508 of the paper feed/conveyance unit 505 or the manual feed tray 509 to the secondary transfer roller 510. The secondary transfer roller 510 collectively transfers the toner images on the intermediate transfer belt 511 to the sheet S. The sheet S on which the toner image is transferred is conveyed to the fixing unit 504. The fixing unit 504 heats and presses the sheet S to melt the toner and fix the toner image on the sheet S. The sheet S on which the toner image is fixed is discharged to the discharge tray 512.

The optical scanning device 2 sequentially starts emission of light beams of magenta, cyan, and black images from the emission start timing of light beams of yellow images. By controlling the emission start timing of the optical scanning device 2 in the sub-scanning direction (rotational direction of the photosensitive drum 25), a full-color toner image without color misregistration is formed on the intermediate transfer belt 511.

[Photosensitive drum and optical scanning device]
FIG. 2 is a diagram illustrating the configuration of the optical scanning device 2 in FIG. The optical scanning device 2 includes a laser driving unit 11, a semiconductor laser (light source) 12, a collimator lens 13, a cylindrical lens 15, a scanner motor 16, an fθ lens 17 and a reflection mirror 18. The scanner motor 16 which is a drive motor rotationally drives the rotor portion 16a including a rotary polygon mirror having a plurality of reflecting surfaces (five in FIG. 2) to deflect the laser light incident on the rotary polygon mirror. Further, the scanner motor 16 outputs a rotation detection signal (hereinafter referred to as an FG signal) 16b according to the rotation angle of the rotary polygon mirror. The image controller 5 outputs a motor control signal 23 (see FIG. 3) to the scanner motor 16. The image controller 5 also outputs a light amount control signal 24 (see FIG. 3) to the laser driver 11 that is a rotation controller.

As shown in FIG. 1, the image control unit 5 is provided outside the optical scanning device 2 and on the main body side of the image forming apparatus 1. The image controller 5 and the optical scanning device 2 are electrically connected via a signal line. The laser light emitted from the semiconductor laser 12 under the control of the laser driving unit 11 travels through the collimator lens 13 and the cylindrical lens 15 to the rotary polygon mirror provided on the rotor unit 16a. The laser beam L1 is deflected by the rotary polygon mirror, and enters the beam detector 20 (hereinafter referred to as BD20) via the fθ lens 17. Upon detecting the laser beam L1, the BD 20, which is a detection unit, outputs a BD signal 21, which is a second rotation cycle signal that determines the reference position of the image region. On the other hand, in the image area where the image is formed on the photosensitive drum 25, the laser beam L2 passes through the fθ lens 17, is reflected by the reflection mirror 18, and scans the photosensitive drum 25 based on the BD signal 21. , An electrostatic latent image is formed.

[Control of scanner motor]
FIG. 3 is a control block diagram showing the configuration of the optical scanning device 2 and the configuration of the image control unit 5. The image control unit 5 has a CPU 503 and a laser scanner control unit 501 (hereinafter, referred to as LS control unit 501). In FIG. 3, the scanner motor 16 outputs the FG signal 16b that is the first rotation cycle signal to the LS control unit 501 of the image control unit 5. Further, the laser light emitted from the semiconductor laser 12 under the control of the laser driving unit 11 is deflected by the rotary polygon mirror mounted on the rotor unit 16a and enters the BD 20, and the BD 20 detects the laser light and outputs the BD signal 21. It is output to the LS control unit 501. An FG signal 16b output from the scanner motor 16 and a BD signal 21 output from the BD 20 are input to the LS control unit 501. Then, the LS control unit 501, which is the rotation control unit, generates the motor control signal 23 based on the measurement result of the cycle of the FG signal 16b or the BD signal 21, and outputs the motor control signal 23 to the motor drive unit 16c of the scanner motor 16. The motor drive unit 16c provided in the scanner motor 16 controls the rotation of the rotor unit 16a on which the rotary polygon mirror is mounted according to the motor control signal 23 from the LS control unit 501. The LS control unit 501 also generates a light amount control signal 24 based on the BD signal 21 and outputs it to the laser drive unit 11 of the optical scanning device 2. The laser driver 11 controls the emission of the semiconductor laser 12 according to the light amount control signal 24.

Further, the CPU 503 has a ROM and a RAM (not shown). The CPU 503, which is a control unit, controls the light emission of the optical scanning device 2 and the rotation of the scanner motor 16 by executing various programs stored in the ROM while using the RAM as a work area. Further, the CPU 503 has a timer which is a time measuring means.

[Configuration of LS control unit]
FIG. 4 is a block diagram showing the configurations of the motor control unit 30 of the LS control unit 501, the mask control unit 40 that controls the rotation reference signal 31 input to the motor control unit 30, and the mask circuit 41. In FIG. 4, the rotation reference signal 31 is a basic signal for generating the motor control signal 23 output to the motor drive unit 16c. Here, if the rotation cycle of the scanner motor 16 can be detected, the signal input to the LS control unit 501 as the rotation reference signal 31 may be the BD signal 21 or the FG signal 16b.

The rotation reference signal 31 input to the LS control unit 501 is masked in the mask circuit 41 connected to the mask control unit 40 according to the mask signal 42 output from the mask control unit 40. The operation of the mask circuit 41, which is the signal output unit, will be described with reference to FIG. FIG. 5 is a timing chart for explaining the operation of the mask circuit 41. In FIG. 5, a) shows the rotation reference signal 31, b) shows the mask signal 42, and c) shows the waveform of the output signal of the mask circuit 41 output to the frequency divider 32. The rotation reference signal 31 shown in a) has a period of Tref, and the beginning of one period is the falling edge of the signal. The mask signal 42 shown in b) is a signal having the same period as the rotation reference signal 31. The mask signal 42 is at a low level until a predetermined time elapses from the falling edge of the rotation reference signal 31, becomes a high level after a predetermined time elapses, and is kept at a high level for a set time Tm. It is a signal that becomes low level when the time Tm elapses. For example, even if an erroneous edge (circled number 1 in the figure) due to mixing of noise or the like occurs during one cycle of the rotation reference signal 31 shown in a), the mask signal 42 during the period when the erroneous edge occurs is Since it is at the high level, the false edge is removed by the mask signal 42. As a result, in the output signal of the mask circuit 41 shown in c), the signal (circled number 2 in the figure) from which the false edge is removed is output. Note that the masking of the rotation reference signal 31 by the mask signal 42 is started after a predetermined time has elapsed from the falling edge of the rotation reference signal 31 in order to reliably catch the falling edge of the rotation reference signal 31. The time setting of the predetermined time may be arbitrary.

Next, the configuration of the motor control unit 30 that is the control means will be described. In FIG. 4, the frequency divider 32 divides the rotation reference signal 31 input through the mask circuit 41 according to the frequency division setting value 33 in order to determine the generation timing of the motor control signal 23. The method of setting the frequency division setting value 33 differs depending on whether the rotation reference signal 31 is the BD signal 21 or the FG signal 16b. Therefore, for example, when the rotation reference signal 31 is the BD signal 21, the frequency division setting value 33 outputs the motor control signal 23 for each rotation of the scanner motor 16, and therefore is the number of mirror surfaces of the rotary polygon mirror. The frequency ratio is “5” (Tdiv 1:5 frequency division in FIG. 6A). On the other hand, when the rotation reference signal 31 is the FG signal 16b, the frequency division setting value 33 is the number of pulses for one rotation of the rotor portion 16a because the motor control signal 23 is output for each rotation of the scanner motor 16. The frequency division ratio is “6” (Tdiv2:6 frequency division in FIG. 6B). The rising edge detection circuit 34a outputs a signal synchronized with the rising edge of the output signal of the frequency divider 32, and the falling edge detection circuit 34b outputs a signal synchronized with the falling edge of the output signal of the frequency divider 32. To do.

The counter 35a counts the cycle of the output signal from the rising edge detection circuit 34a with a main clock (indicated by MCLK in the drawing) 39 starting from the rising edge of the output signal from the rising edge detection circuit 34a. The reference cycle set value 38 is stored in, for example, a storage circuit. The reference cycle set value 38 is a value obtained by converting a predetermined rotation speed (time required for the rotary polygon mirror to make one revolution) of the scanner motor 16 that generates the signal selected as the rotation reference signal 31 into time (count value). The counter 35a starts counting when it detects the rising edge of the output signal from the rising edge detection circuit 34a, counts up to the reference cycle set value 38, outputs a high level signal during this period, and exceeds the reference cycle set value 38. Outputs a low level signal. On the other hand, the counter 35b starts counting when it detects the falling edge of the output signal from the falling edge detection circuit 34b, counts up to the reference cycle set value 38, and outputs a high level signal during this period to output the reference cycle set value. When it exceeds 38, a low level signal is output. As described above, the counter 35a and the counter 35b use a high level signal or a low level signal to indicate the state in which the reference period setting value 38 is counted each time the rotary polygon mirror makes one rotation, by the OR gate 36 and the NAND gate. Output to the gate 37. Based on the signals output from the counters 35a and 35b, the motor control unit 30 uses the output from the OR gate 36 to generate the acceleration signal 23a when the rotation reference signal 31 has a long cycle, and the optical scanning device It outputs to the motor drive unit 16c of the second scanner motor 16. On the other hand, when the cycle of the rotation reference signal 31 is short, the motor control unit 30 uses the output from the NAND gate 37 to generate the deceleration signal 23b and outputs it to the motor drive unit 16c of the scanner motor 16 of the optical scanning device 2. To do.

[Generation of motor control signal]
FIG. 6 is a timing chart illustrating a method of generating the motor control signal 23 that controls the scanner motor 16. FIG. 6A shows a timing chart when the BD signal 21 is the rotation reference signal 31, and FIG. 6B shows a timing chart when the FG signal 16b is the rotation reference signal 31. There is.

In FIG. 6A, the signal waveforms in the LS control unit 501 shown in FIG. 4 are shown in the vertical axis direction, and the horizontal axis shows time. In FIG. 6A, a) shows the waveform of the rotation reference signal 31 input to the LS control unit 501. In this case, the signal waveform when the BD signal 21 is selected as the rotation reference signal 31 is shown. Shows. b) shows a signal waveform of the mask signal 42 output from the mask control unit 40. c) shows a signal waveform obtained by dividing the rotation reference signal 31 output from the frequency divider 32. In FIG. 6A, since the BD signal 21 is selected as the rotation reference signal 31, the number of faces of the rotating polygon mirror is set to 5 as the frequency division setting value 33 (Tdiv 1:5 frequency division in the figure). ).

d) shows the signal waveform of the output signal from the rising edge detection circuit 34a. The rising edge detection circuit 34a outputs a low level pulse when detecting the rising edge of the signal output from the frequency divider 32. e) shows the signal waveform of the output signal from the falling edge detection circuit 34b. The falling edge detection circuit 34b outputs a low level pulse when detecting the falling edge of the signal output from the frequency divider 32. f) shows the signal waveform of the output signal of the counter 35a that measures the cycle of the output signal from the rising edge detection circuit 34a. In the figure, “1 rotation/reference cycle” indicates the period of the count value corresponding to the reference cycle set value 38. The counter 35a starts counting when it detects the low-level pulse output from the rising edge detection circuit 34a and outputs a high-level signal, and when the "one rotation/reference period" ends, the output signal is changed from the high level. Switch to low level. g) shows the signal waveform of the output signal of the counter 35b that measures the period of the output signal from the falling edge detection circuit 34b. The counter 35b starts counting when a low-level pulse output from the falling edge detection circuit 34b is detected and outputs a high-level signal, and when the "one rotation/reference period" ends, the output signal is set to a high level. To low level.

h) shows the signal waveform of the motor control signal 23 (acceleration signal 23a, deceleration signal 23b). The acceleration signal 23a indicates the output signal of the OR gate 36 to which the output signal of the counter 35a shown in f) and the output signal of the counter 35b shown in g) are input. On the other hand, the deceleration signal 23b indicates the output signal of the counter 35a shown in f) and the output signal of the NAND gate 37 to which the output signal of the counter 35b shown in g) is input.

The rotation reference signal 31 shown in a) shows a signal waveform in which the rotation speed of the scanner motor 16 gradually increases from a slower than steady state to a faster than steady state. When the rotation speed of the scanner motor 16 is slower than the steady state, the cycle of the signal output from the frequency divider 32 becomes long, and the cycle of the signals output from the rising edge detection circuit 34a and the falling edge detection circuit 34b also becomes longer. become longer. As a result, the output signals from the counters 35a and 35b also have a low level time after the reference cycle set value 38 has passed, and the output signals from the counters 35a and 35b are both at a low level, that is, the reference cycle set value 38. Longer time will occur. Therefore, the acceleration signal 23a is output during the periods Tacc1 to Tacc3 in which the output signals from the OR gate 36 and the counters 35a and 35b are both at the low level.

On the other hand, when the rotation speed of the scanner motor 16 is faster than the steady state, the cycle of the signal output from the frequency divider 32 becomes shorter, and the signal output from the rising edge detection circuit 34a and the falling edge detection circuit 34b becomes shorter. The cycle becomes shorter. As a result, the output signals from the counters 35a and 35b also have a low level time after the reference cycle set value 38 has passed, and the output signals from the counters 35a and 35b are both at a high level, that is, the reference cycle set value 38. There will be overlapping periods. Therefore, the deceleration signal 23b is output during the periods Tdec1 to Tdec3 in which the output signals from the NAND gate 37 from the counters 35a and 35b are both at the high level.

FIG. 6B shows a timing chart when the FG signal 16b is used as the rotation reference signal 31. Each signal waveform shown in FIG. 6B is the same as that in FIG. 6A, and the description thereof is omitted here. In FIG. 6B, since the FG signal 16b is selected as the rotation reference signal 31, the number of pulses 6 output by the rotor unit 16a of the scanner motor 16 for each rotation is set as the frequency division setting value 33. (Tdiv2 divided by 6 in the figure). The rotation reference signal 31 shown in a) shows a signal waveform in which the rotation speed of the scanner motor 16 gradually increases from a slower than steady state to a faster than steady state. When the rotation speed of the scanner motor 16 is slower than the steady state, the output signals from the counters 35a and 35b are also at the low level time after the reference period set value 38 has passed, as in the case of FIG. 6A described above. Becomes longer. Therefore, the output signals from the counters 35a and 35b are both at the low level, that is, longer than the reference period setting value 38. Therefore, the acceleration signal 23a is output during the periods Tacc4 to Tacc6 in which the output signals from the OR gate 36 and the counters 35a and 35b are both at the low level.

On the other hand, even when the rotation speed of the scanner motor 16 is higher than the steady state, the output signals from the counters 35a and 35b are also at the low level after the reference period set value 38 has passed, as in the case of FIG. 6A described above. Time will be shortened. Therefore, there occurs a time when the output signals from the counters 35a and 35b are both at a high level, that is, a period in which the period of the reference cycle set value 38 overlaps. Therefore, during the periods Tdec4 to Tdec6 in which the output signals from the NAND gate 37 from the counters 35a and 35b are both at the high level, the deceleration signal 23b is output.

[Control of motor drive unit]
Further, the motor drive unit 16c of the scanner motor 16 controls the rotation of the scanner motor 16 shown in Table 1 according to the motor control signal 23 output from the motor control unit 30, that is, the acceleration signal 23a and the deceleration signal 23b. Table 1 is a table showing the control performed by the motor drive unit 16c according to the acceleration signal 23a and the deceleration signal 23b.

In Table 1, L and H shown in the columns of the acceleration signal and the deceleration signal indicate low level and high level, respectively. Further, the column of the motor drive unit control describes the control of the scanner motor 16 performed according to the states of the acceleration signal 23a and the deceleration signal 23b. When the acceleration signal 23a is L and the deceleration signal 23b is H, the motor drive unit 16c performs acceleration control because the rotation speed of the scanner motor 16 is slow. When the acceleration signal 23a is H and the deceleration signal 23b is L, the motor drive unit 16c performs deceleration control because the rotation speed of the scanner motor 16 is high. When the acceleration signal 23a is H and the deceleration signal 23b is H, the motor driving unit 16c does not perform the deceleration/acceleration control because the scanner motor 16 is rotating at a predetermined rotation speed and maintains the current state. Control. When the acceleration signal 23a is L and the deceleration signal 23b is L, the motor drive unit 16c cuts off the current supply to the scanner motor 16 and controls the rotation of the scanner motor 16.

[Behavior of motor control signal due to false edge of rotation reference signal]
FIG. 7 is a timing chart illustrating the output of the motor control signal 23 when an erroneous edge occurs in the rotation reference signal 31 due to noise or the like, and as a result, a cycle abnormality of the rotation reference signal 31 occurs. In the following description, detailed description of the signals described in FIG. 6 will be omitted. Note that, in FIG. 7, the BD signal 21 is input to the rotation reference signal 31.

FIG. 7A is a timing chart illustrating the behavior of the motor control signal 23 when an erroneous edge occurs in the rotation reference signal 31 and the cycle of the rotation reference signal 31 is detected to be shorter than when it is stationary. .. In FIG. 7A, a) shows the signal waveform of the rotation reference signal 31, and the period Tbd shows the cycle of the rotation reference signal 31. b) is a signal waveform of the mask signal 42, the period (time width) Tm of the mask signal 42 is a fixed value (predetermined period), and in this embodiment, the rotation reference signal 31 is changed from the falling base point of the rotation reference signal 31. It is set up to 80% of the cycle. In the mask area where the mask signal 42 is at the high level ON, the input of the rotation reference signal 31 is not accepted. Therefore, for example, even if the rotation reference signal 31 has an erroneous edge due to noise, it is removed. Become. c) is a signal waveform of the output signal of the mask circuit 41. The mask circuit 41 outputs the rotation reference signal 31 after masking the rotation reference signal 31 shown in a) with the mask signal 42 shown in b). .. d) is a signal waveform showing an output signal of the frequency divider 32, e) is an output signal of the counter 35b, and f) is a signal waveform showing an output signal of the counter 35a. g) is a signal waveform of the motor control signal 23 (acceleration signal 23a, deceleration signal 23b).

In FIG. 7A, a) shows that noise is superimposed on the rotation reference signal 31 and false edges 1 and 2 are generated. In the case of the false edge 1, since the generated timing is the mask period Tm of the mask signal 42 shown in b), the false edge 1 is removed from the output signal of the mask circuit 41 in c). Can be seen (circle number 1 in the figure). On the other hand, in the case of the false edge 2, the occurring timing is outside the mask period Tm of the mask signal 42 shown in b). Therefore, since the false edge 2 cannot be removed by the mask signal 42, it can be seen that the false edge 2 is not removed by the output signal of the mask circuit 41 in c) and is output as it is (circled number 2 in the figure). .. As a result, the low-level period of the output signal of the frequency divider 32 becomes shorter than the original period, and the deceleration signal 23b of the period Tdec is erroneously output from the NAND gate 37 (circled numeral 4 in the figure). Further, since the false edge 2 is not removed by the mask signal 42, the false edge 2 is erroneously detected as the falling edge of the rotation reference signal 31, and the mask signal 42 is output during a period other than the original mask period (b in the figure). ). As a result, it can be seen that the falling edge of the rotation reference signal 31 immediately after the false edge 2 is masked and removed from the output signal of the mask circuit 41 (circled numeral 3 in the figure).

FIG. 7B is a timing chart illustrating the behavior of the motor control signal 23 when a signal omission occurs in the rotation reference signal 31 and the period of the rotation reference signal 31 is detected longer than when it is stationary. .. In FIG. 7B, the signal waveforms shown in a) to g) are the same as those in FIG. 7A, and a description thereof will be omitted here. In a) of FIG. 7B, it is shown that the rotation reference signal 31 has a signal drop of the third falling pulse (circled numeral 1 in the figure). As a result, the low level period of the output signal of the frequency divider 32 shown in d) becomes longer than the steady state, and the acceleration signal 23a of the period Tacc is erroneously output from the OR gate 36 (circled number 2 in the figure). ).

FIG. 7C is a timing chart illustrating the output of the motor control signal 23 when a signal omission occurs in the rotation reference signal 31 and the cycle of the rotation reference signal 31 is detected longer than when it is stationary. .. In FIG. 7C, each signal waveform except the mask signal 42 shown in b) is the same as that in FIGS. 7A and 7B, and the description thereof is omitted here. The mask period Tm of the mask signal 42 shown in b) is a method set according to the cycle of the rotation reference signal 31. Therefore, the mask control unit 40 outputs the mask signal 42 for masking the period of n% of the cycle of the rotation reference signal 31 detected immediately before to the mask circuit 41. For example, the mask periods Tm1, Tm2, and Tm3 shown in b) are calculated by the following (Formula 1), (Formula 2), and (Formula 3), and the cycle of the k-th mask period Tmk is defined by (Formula 4). You can ask. The cycles Tbd0, Tbd1, Tbd2, and Tbd(k-1) indicate the cycles of the rotation reference signal 31 detected immediately before the mask periods Tm1, Tm2, Tm3, and Tmk, respectively.
Mask period Tm1=cycle Tbd0×n% (Equation 1)
Mask period Tm2=cycle Tbd1×n% (Equation 2)
Mask period Tm3=cycle Tbd2×n% (Equation 3)
Mask period Tmk=cycle Tbd(k−1)×n% (Equation 4)

In (a) of FIG. 7C, it is shown that the rotation reference signal 31 has a third missing pulse signal (circled number 1 in the figure). Therefore, the cycle of the second rotation reference signal 31 becomes long, and as a result, the period of the mask period Tm3 of the mask signal 42 is extended (circled number 2 in the figure). Therefore, the falling edge of the original rotation reference signal 31 is masked by the mask period Tm3 of the mask signal (circled number 3 in the figure). As a result, the low level period of the output signal of the frequency divider 32 shown in d) becomes longer than in the steady state, and the OR gate 36 erroneously outputs the acceleration signal 23a of the period Tacc' (indicated by circled numbers in the figure). 4). In the mask signal 42 output from the conventional mask control unit 40 as described above, the motor control signal 23 may be erroneously output due to a missing signal or a false edge of the rotation reference signal 31. Therefore, it may take time until the rotation of the scanner motor 16 returns to the normal state, which affects the image forming operation.

[Configuration of mask control unit]
FIG. 8 is a control block diagram showing the configuration of the mask control unit 40 of the LS control unit 501 of this embodiment. The mask control unit 40 that is a signal output unit includes a counter 45, a mask signal generation unit 43, a period setting unit 47, an abnormal period detection unit 46 that is a period detection unit, and a mask signal control unit 49. Here, the BD signal 21 is selected as the rotation reference signal 31.

The counter 45 inputs the main clock (indicated by MCLK in the drawing) 39, counts the cycle of the rotation reference signal 31 for which the BD signal 21 is selected, and outputs the count value to the abnormal cycle detection unit 46. The counter 45 resets the count value when it detects a falling edge in the rotation reference signal 31. The abnormal cycle detection unit 46 compares the count value input from the counter 45 with the set value stored in the cycle setting unit 47, and detects the low level abnormality detection signal 51 (mask inhibition signal) or the high level abnormality. The detection signal 51 (mask enable signal) is output to the mask signal controller 49. That is, if the count value immediately before the counter 45 detects the falling edge of the rotation reference signal 31 and resets the count value is equal to or less than the count value N _MASK corresponding to the mask setting value 44, the abnormal cycle detection unit 46 , And outputs the low-level abnormality detection signal 51. Further, the abnormal cycle detection unit 46, when the count value of the counter 45 immediately before resetting is equal to or greater than the count value N _BD+α corresponding to a cycle longer than the cycle (BD) of the rotation reference signal 31 in the steady state by a margin (α). Also, the low-level abnormality detection signal 51 is output. On the other hand, when the count value immediately before the counter 45 resets the count value is larger than the count value N _MASK and less than the count value N _BD+α , the abnormal cycle detection unit 46 outputs the high-level abnormality detection signal 51. To do. The mask signal generation unit 43, which is a signal generation unit, outputs to the mask signal control unit 49 a signal having the period set by the mask setting value 44 as the mask period, with the falling edge of the rotation reference signal 31 as the base point. The mask setting value 44 is set to a period of about 80 to 90% of the stationary period of the rotation reference signal 31. The mask signal control unit 49 generates a mask signal 42 based on the output from the mask signal generation unit 43 and the abnormality detection signal 51 output from the abnormal period detection unit 46, and outputs the mask signal 42 to the mask circuit 41.

[Mask signal generation]
FIG. 9 is a timing chart illustrating a method of generating the mask signal 42 that masks the rotation reference signal 31. First, a conventional method of generating the mask signal 42 will be described with reference to FIG. 9A, a) shows the rotation reference signal 31, b) shows the mask signal 42 output from the mask control unit 40 shown in FIG. 4, and c) is output from the mask circuit 41. The signal after the rotation reference signal 31 is masked by the mask signal 42 is shown. The rotation reference signal 31 shown in a) includes a signal having a cycle longer than that in the steady state and a signal having a cycle shorter than that in the steady state. In the mask signal 42 shown in b), a predetermined mask setting period Tm is set after a predetermined time elapses at each falling edge of the rotation reference signal 31. Therefore, for example, when the rotation speed of the scanner motor 16 becomes faster than in the steady state, the cycle of the rotation reference signal 31 becomes shorter. Then, when the falling edge of the rotation reference signal 31 overlaps the mask setting period Tm, the signal output from the mask circuit 41 has a falling edge omission (a signal omission indicated by c in the figure). .. When the missing signal of the rotation reference signal 31 occurs, it is erroneously detected that the cycle of the rotation reference signal 31 is long, and the acceleration signal 23a is erroneously output as described in FIGS. 7B and 7C described above. It will be.

Next, a method of generating the mask signal 42 in this embodiment will be described with reference to FIG. In FIG. 9B, a) shows the rotation reference signal 31 having the same signal waveform as that of a) in FIG. 9A. In the rotation reference signal 31 shown in a), it is assumed that the second missing edge signal is missing. b) shows the count value output by the counter 45. In b), “count value≧N _BD+α ” indicates a period in which the count value of the counter 45 is equal to or greater than the count value N _BD+α corresponding to a cycle longer than the cycle of the rotation reference signal 31 in the steady state. “Count value≦N _MASK ”indicates a period in which the count value of the counter 45 is equal to or less than the count value N _MASK corresponding to the mask setting value 44. “N _MASK <count value <N _BD+α ” indicates that the count value of the counter 45 is a period of the count value corresponding to the cycle within the allowable range of the rotation reference signal 31. c) shows the abnormality detection signal 51 output from the abnormal cycle detection unit 46. When the abnormal cycle detection unit 46 detects that the cycle of the rotation reference signal 31 is a normal period (N _MASK <count value <N _BD+α ) based on the count value of the counter 45, the high level abnormality detection signal 51 Is output. On the other hand, when the abnormal cycle detection unit 46 detects that the cycle of the rotation reference signal 31 is an abnormal period (count value ≤ N _MASK , count value ≥ N _BD+α ) based on the count value of the counter 45, the abnormal level detection section 46 makes a low level. The abnormality detection signal 51 is output. As shown in c), when the cycle of the rotation reference signal 31 is extended and an abnormality in the count value of the counter 45 is detected, the abnormality cycle detection unit 46 sets the abnormality detection signal 51 to a low level when the abnormality is detected. To do. On the other hand, when the abnormal cycle detection unit 46 detects that the count value of the counter 45 is normal, it sets the abnormality detection signal 51 to a high level. Further, when the cycle of the rotation reference signal 31 is shortened and the abnormality of the count value of the counter 45 is detected, the abnormality cycle detection unit 46 sets the abnormality detection signal 51 to a low level.

d) shows a signal output by the mask signal generation unit 43, and each time the falling edge of the rotation reference signal 31 is detected, the period set by the mask setting value 44 is set as the mask period based on the falling edge. The signal to be Tm is output to the mask signal controller 49. The reason why the mask period Tm is started after the lapse of a predetermined time from the falling edge of the rotation reference signal 31 is to reliably catch the falling edge of the rotation reference signal 31, and the time setting may be arbitrary. e) shows the mask signal 42 output from the mask signal controller 49 to the mask circuit 41. The mask signal control unit 49 generates the mask signal 42 by the logical product (AND) of the abnormality detection signal 51 output from the abnormal period detection unit 46 and the signal output from the mask signal generation unit 43. Therefore, when the normal period Tdet1 of the abnormality detection signal 51 is shorter than the mask setting value 44, the period Tm' of the mask signal 42 also becomes short. f) shows the rotation reference signal 31 after being input to the mask circuit 41 and masked by the mask signal 42. Compared with the rotation reference signal 31 output from the mask circuit 41 shown in c) of FIG. 9A, the rotation reference signal 31 shown in f) of FIG. 9B has a missing signal of the rotation reference signal 31. You can see that not. As a result, it is possible to reduce the acceleration/deceleration control in which the motor control signal 23 is erroneously output due to the omission of the rotation reference signal 31.

As described above, in this embodiment, the mask signal 42 in which the setting of the mask period Tm is variable is generated based on the abnormality detection signal 51. That is, when the cycle abnormality of the rotation reference signal 31 is detected, the mask signal 42 in which the mask period Tm is not set is generated, and when the cycle abnormality of the rotation reference signal 31 is not detected, the mask period Tm is set. The set mask signal 42 is generated. As described above, when the cycle abnormality of the rotation reference signal 31 occurs, the mask signal 42 in which the mask period Tm is set is not output in the mask inhibition section of the abnormality detection signal 51, so that the rotation reference signal 31 can be re-acquired. It will be possible. As a result, the operation of the scanner motor 16 returns quickly to the normal state.

As described above, according to the present embodiment, it is possible to control the setting of the mask signal when the abnormality of the rotation reference signal occurs, and quickly return the scanner motor to the stable state.

In the first embodiment, the mask signal 42 is output for each cycle of the rotation reference signal 31 according to the cycle state of the rotation reference signal 31 immediately before. In the second embodiment, an embodiment will be described in which control is performed such that the mask signal 42 is not output until the cycle of the rotation reference signal 31 stabilizes a predetermined number of times or more.

[Configuration of mask control unit]
FIG. 10 is a control block diagram showing the configuration of the mask control unit 40 of the LS control unit 501 of this embodiment. 10 is different from the configuration of the mask control unit 40 shown in FIG. 8 of the first embodiment in that a stability determination unit 48 is added. An abnormality detection signal 51 is input to the stability determination unit 48 from the rotation reference signal 31 and the abnormality cycle detection unit 46. The stability determination unit 48 determines the state of the abnormality detection signal 51 as the rotation reference signal 31 in order to determine that the stable period in which the rotation reference signal 31 has the same period as the steady state is continuous and continues for a predetermined period or more. Measure in cycle units. When the stability determination unit 48 determines that the stable period of the cycle of the rotation reference signal 31 continues for a predetermined period or longer, the stability determination unit 48 outputs the determination signal of the low-level pulse signal to the mask signal control. It is output to the unit 49. The mask signal control unit 49 causes the mask signal control unit 49 to generate a mask control signal 50, which will be described later, based on the abnormality detection signal 51 output from the abnormal period detection unit 46 and the determination signal from the stability determination unit 48. .. Then, the mask signal control unit 49, in response to the mask signal output from the mask signal generation unit 43, sets the mask signal 42 in the mask control signal 50 so that the mask signal is not output during the mask signal output prohibition period. Is generated and output. It should be noted that the other members constituting the mask control unit 40 are the same as those described in FIG. 8 of the first embodiment, and are denoted by the same reference numerals, and the description thereof will be omitted here.

[Mask signal generation]
FIG. 11 is a timing chart illustrating a method of generating the mask signal 42 that masks the rotation reference signal 31. In FIG. 11, a) shows the rotation reference signal 31. In the rotation reference signal 31 shown in a), it is assumed that the second missing edge signal is missing. b) shows the count value output by the counter 45. In b), “count value≧N _BD+α ” indicates a period in which the count value of the counter 45 is larger than the count value N _BD+α corresponding to a cycle longer than the cycle of the rotation reference signal 31 in the steady state. “Count value≦N _MASK ”indicates a period in which the count value of the counter 45 is smaller than the count value N _MASK corresponding to the mask setting value 44. “N _MASK <count value<N _BD+α ” indicates that the count value of the counter 45 is a period of the count value corresponding to the cycle of the rotation reference signal 31. c) shows an abnormality detection signal 51 output from the abnormal cycle detection unit 46. As shown in c), when the period of the rotation reference signal 31 is extended or shortened and the count value of the counter 45 is abnormal, the abnormal period detection unit 46 sets the abnormality detection signal 51 to a low level. On the other hand, when the abnormal cycle detection unit 46 detects that the count value of the counter 45 is normal, it sets the abnormality detection signal 51 to a high level. d) shows the count value of the internal counter of the stability determination unit 48, which is a counter for measuring a period in which the cycle of the rotation reference signal 31 is normal. When the cycle of the rotation reference signal 31 is determined to be abnormal and the abnormality detection signal 51 is at a low level, the count value of the internal counter of the stability determination unit 48 is reset to 0. On the other hand, the cycle of the rotation reference signal 31 is determined to be normal, and when the abnormality detection signal 51 is at the high level, the counter is counted up when the falling edge of the rotation reference signal 31 is detected. When the count value of the internal counter of the stability determination unit 48 reaches 20, the stability determination unit 48 determines that the rotation reference signal 31 is in a stable state and outputs a low level pulse signal (e in the figure). reference). The count value of the internal counter of the stability determination unit 48 is determined, for example, based on the convergence time until the stable rotation speed of the scanner motor 16.

The mask control signal 50 is a signal inside the mask signal control unit 49 generated by the mask signal control unit 49. In the mask control signal 50, the abnormal cycle detection unit 46 determines that the rotation reference signal 31 has a cyclic abnormality, and from the time (timing) when the abnormality detection signal 51 is set to a low level, the stability determination unit 48 outputs a low-level pulse signal. Is output until the mask signal setting prohibition period. The mask control signal 50 is set to the low level during the mask signal setting prohibition period. g) shows a signal output from the mask signal generation unit 43, and the mask signal generation unit 43 uses the falling edge of the rotation reference signal 31 as a base point until the period Tm which is the set value of the mask set value 44. A mask area is generated and output to the mask signal controller 49. The mask signal 42 shown in h) is a signal generated by the mask signal control unit 49 by a logical product (AND) of the mask control signal 50 and the signal output from the mask signal generation unit 43. Therefore, the mask signal 42 is a signal in which the mask region of the period Tm is not provided in the mask signal setting prohibition period in which the mask control signal 50 is at the low level. i) shows the rotation reference signal 31 after being input to the mask circuit 41 and masked by the mask signal 42, and this signal is output to the motor control unit 30.

As described above, according to the present embodiment, when the cycle abnormality of the rotation reference signal 31 occurs, the output of the mask signal 42 is stopped, and after the cycle of the rotation reference signal 31 is stabilized for a predetermined period, the masking is performed. The control for re-outputting the signal 42 is performed. As a result, the re-acquisition of the rotation reference signal 31 is stably performed, and the operation of the scanner motor 16 is quickly returned to the normal state.

As described above, according to the present embodiment, it is possible to control the setting of the mask signal when the abnormality of the rotation reference signal occurs, and quickly return the scanner motor to the stable state.

In the second embodiment, the embodiment in which the control for outputting the mask signal is performed after the cycle of the rotation reference signal 31 is stable for a predetermined period or more has been described. In the third embodiment, an embodiment will be described in which, after detecting a stable rotation of the scanner motor 16, when the cycle of the rotation reference signal 31 becomes stable for a predetermined period or longer, a mask signal is output.

[Configuration of mask control unit]
FIG. 12 is a control block diagram showing the configuration of the mask control unit 40 of the LS control unit 501 of this embodiment. In FIG. 12, compared with the configuration of the mask control unit 40 shown in FIG. 10 of the second embodiment, the motor control signal from the motor control unit 30 to the mask signal control unit 49 is a motor lock signal 52 which is a state signal indicating the rotation state of the scanner motor 16. The difference is that is output. The motor lock signal 52 outputs a high level when the rotation of the scanner motor 16 is stable, and outputs a low level when the rotation of the scanner motor 16 is not stable. The mask signal control unit 49 generates the mask control signal 50 based on the abnormality detection signal 51 output from the abnormal period detection unit 46, the output signal from the stability determination unit 48, and the motor lock signal 52. When the motor lock signal 52 is at a low level and the rotation of the scanner motor 16 is not stable, the mask signal control unit 49 does not generate the mask control signal 50 in which the mask inhibition section is released. Further, other members constituting the mask control unit 40 are the same as the members described in FIG. 8 of the first embodiment and FIG. 10 of the second embodiment, and are denoted by the same reference numerals, and the description thereof is omitted here. ..

[Generation of motor lock signal]
FIG. 13 is a diagram for explaining the relationship between the rotation reference signal 31 and the motor lock signal 52. The upper diagram (upper diagram) is a graph showing the cycle of the rotation reference signal 31 generated by the rotation of the scanner motor 16, the vertical axis shows the cycle T of the rotation reference signal 31, and the horizontal axis shows the time t. Show. As shown in the above figure, when the scanner motor 16 starts to start, the cycle of the rotation reference signal 31 converges within the swing width T ₁ centering on the reference cycle T ₀ as time passes. In the present embodiment, when the cycle of the rotation reference signal 31 is maintained within the lock range T ₁ that is the swing width around the reference cycle T ₀ for the predetermined time T2 or more, the motor control unit 30 determines It is determined that the scanner motor 16 is in a stable rotation state. Then, the motor control unit 30 switches the motor lock signal 52 from low level to high level.

[Mask signal generation]
FIG. 14 is a timing chart illustrating a method of generating the mask signal 42 that masks the rotation reference signal 31. In FIG. 14, (a) shows the rotation reference signal 31 after the scanner motor 16 is activated after the power is turned on (Po_ON in the figure). In the figure, the rotation of the scanner motor 16 is unstable until timing (A), and the motor lock signal 52 shown in b) is at a low level. At timing (A), the rotation of the scanner motor 16 becomes stable, and the motor lock signal 52 output from the motor control unit 30 becomes high level. c) shows the count value output by the counter 45. When the rotation of the scanner motor 16 becomes stable and the motor lock signal 52 becomes high level, the count value of the counter 45 becomes “N _MASK <count value <N _BD+α ”. Then, d) shows the abnormality detection signal 51 output from the abnormal cycle detection unit 46, but when the abnormal period detection unit 46 detects that the count value of the counter 45 is normal, the abnormality detection signal 51 goes high. Set to level. e) shows the count value of the internal counter of the stability determination unit 48, which counts the number of periods in which the cycle of the rotation reference signal 31 is normal. As for the count value of the internal counter of the stability determination unit 48, when the rotation of the scanner motor 16 becomes stable, the motor lock signal 52 becomes high level, and the abnormality detection signal 51 becomes high level, the counter falls of the rotation reference signal 31. It is incremented each time an edge is detected. When the count value of the internal counter of the stability determination unit 48 reaches 20, the stability determination unit 48 determines that the rotation reference signal 31 is in a stable state and outputs a low level pulse signal (f in the figure). ). Note that the count value of the internal counter of the stability determination unit 48 is determined based on, for example, the convergence time until the stable rotation speed of the scanner motor 16.

In the mask control signal 50 shown in (g), the abnormal period detection unit 46 determines that the period reference signal 31 is abnormal and sets the abnormality detection signal 51 to a low level, and then the stability determination unit 48 outputs a low level pulse. The period until the signal is output is the mask signal setting prohibition period. Then, the mask control signal 50 is output at a low level during the mask signal setting prohibition period. h) shows a signal output from the mask signal generation unit 43, and the mask signal generation unit 43 uses the falling edge of the rotation reference signal 31 as a base point until the period Tm which is the set value of the mask set value 44. A mask area is generated and output to the mask signal controller 49. The mask signal 42 shown in i) is a signal generated by a logical product (AND) of the motor lock signal 52, the mask control signal 50, and the signal output from the mask signal generation unit 43 in the mask signal control unit 49. is there. The mask signal 42 is a signal in which no mask region is provided while the mask control signal 50 is at a low level. j) shows the rotation reference signal 31 after being input to the mask circuit 41 and masked by the mask signal 42, and this signal is output to the motor control unit 30.

As described above, in this embodiment, when the scanner motor 16 is started and the rotation is stable, the high-level motor lock signal 52 is output, and the mask area is set until the rotation reference signal 31 becomes stable for a predetermined period. The control for stopping the output of the mask signal 42 thus generated is performed. As a result, the rotation reference signal 31 can be acquired again, and the operation of the scanner motor 16 can be quickly returned to the normal state. In the present embodiment, the motor lock signal 52 is output to the mask signal control unit 49, but is output to, for example, the stability determination unit 48, and the stability determination unit 48 reflects the state of the motor lock signal 52. May be output to the mask signal controller 49.

As described above, according to the present embodiment, it is possible to control the setting of the mask signal when the abnormality of the rotation reference signal occurs, and quickly return the scanner motor to the stable state.

In the first to third embodiments, the generation of the mask signal 42 by the mask control unit 40 of the LS control unit 501 has been described. In Example 4, an example in which the CPU 503 of the image control unit 5 detects an abnormality of the scanner motor 16 based on various signals output from the LS control unit 501 and displays the alarm on the operation unit 140 to notify an alarm. explain.

[Configuration of image control unit]
FIG. 15 is a block diagram showing the configuration of the image control unit 5 having the LS control unit 501 and the CPU 503. In FIG. 15, as compared with the configuration of the LS control unit 501 shown in FIG. 12 of the third embodiment, the motor lock signal 52 is output from the motor control unit 30 to the CPU 503, and the mask control signal from the mask signal control unit 49. The difference is that 50 is output to the CPU 503. The mask control signal 50 is a signal inside the mask signal control unit 49 generated by the mask signal control unit 49, but in this embodiment, it is a signal output to the CPU 503. The CPU 503 detects the state of the scanner motor 16 based on the signal states of the motor lock signal 52 and the mask control signal 50, and when an abnormality of the scanner motor 16 is detected, notifies the display unit of the operation unit 140 of the abnormality. Message is displayed. Note that the other members shown in FIG. 15 are the same as the members described in FIG. 12 of the third embodiment, the same reference numerals are given, and the description thereof is omitted here.

[Control sequence for scanner motor abnormality detection]
FIG. 16 is a flowchart showing a control sequence for detecting an abnormality in the scanner motor 16. The process shown in FIG. 16 is started when the abnormality of the scanner motor 16 is detected and is executed by the CPU 503. Note that the process shown in FIG. 16 is for detecting abnormality of the scanner motor 16 of one optical scanning device 2. However, when performing abnormality detection of the scanner motor 16 of a plurality of optical scanning devices 2, FIG. It is assumed that the processes shown in are executed in parallel.

In S101, the CPU 503 activates the scanner motor 16 via the LS control unit 501, and resets the abnormality counter that counts the abnormal state of the scanner motor 16. Further, the CPU 503 resets and starts the timer. In S102, the CPU 503 determines whether the rotation of the scanner motor 16 is stable, based on the state of the motor lock signal 52 output from the motor control unit 30 of the LS control unit 501. When the output of the motor lock signal 52 is at high level, the CPU 503 determines that the rotation of the scanner motor 16 is stable, and advances the process to S104. On the other hand, when the output of the motor lock signal 52 is low level, the CPU 503 determines that the rotation of the scanner motor 16 is not stable, and advances the process to S103. In S103, the CPU 503 refers to the timer and determines whether or not a predetermined time has elapsed since the scanner motor 16 was activated. If the CPU 503 determines that the predetermined time has passed, the process proceeds to S110, and if the predetermined time has not passed, the process returns to S102.

In S104, the CPU 503 resets and starts the timer. In S105, the CPU 503 determines whether the cycle of the rotation reference signal 31 output from the scanner motor 16 is normal, based on the state of the mask control signal 50 output from the mask signal control unit 49. If the CPU 503 determines that the mask control signal 50 is at high level and the cycle of the rotation reference signal 31 is normal, the CPU 503 ends the process. On the other hand, when the CPU 503 determines that the mask control signal 50 is at low level and the cycle of the rotation reference signal 31 is not normal, the CPU 503 advances the process to S106. In S106, the CPU 503 refers to the timer and determines whether a predetermined time has elapsed. If the CPU 503 determines that the predetermined time has passed, the process proceeds to step S107, and if the predetermined time has not passed, the process returns to step S105.

In S107, the CPU 503 updates the abnormality counter. In S107, the CPU 503 refers to the abnormality counter, advances the process to S109 when it is determined that the count value is 2 or more, and returns the process to S102 when it is determined that the count value is less than 2. .. In S109, the CPU 503 displays alarm information that the cycle of the rotation reference signal 31 is abnormal on the display unit of the operation unit 140. In S110, the CPU 503 displays alarm information indicating that the scanner motor 16 is abnormal on the display unit of the operation unit 140. In S111, the CPU 503 stops the scanner motor 16 via the LS control unit 501, and ends the processing.

As described above, according to the present embodiment, the abnormality of the scanner motor can be detected by detecting the state of the scanner motor 16 based on the motor lock signal 52 and the mask control signal 50.

As described above, according to the present embodiment, it is possible to control the setting of the mask signal when the abnormality of the rotation reference signal occurs, and quickly return the scanner motor to the stable state.

2 Optical Scanning Device 5 Image Control Unit 16 Scanner Motor 30 Motor Control Unit 41 Mask Circuit 43 Mask Signal Generation Unit 46 Abnormal Period Detection Unit

Claims (12)

An image forming apparatus comprising: an optical scanning device that exposes a photoconductor; and a control unit that controls the optical scanning device,
The optical scanning device,
A motor for driving a rotating polygon mirror that deflects the light beam to expose the photoconductor with the light beam emitted from a light source;
A rotation control unit for controlling the rotation of the motor,
Have
The control unit is
A signal generation unit that generates a mask signal for removing noise in the rotation reference signal generated according to the rotation of the motor;
A mask permission signal for detecting the cycle of the rotation reference signal and permitting masking of the rotation reference signal by the mask signal according to the detected cycle of the rotation reference signal, or masking of the rotation reference signal by the mask signal A cycle detection unit that outputs a mask prohibition signal that prohibits
When the mask permission signal is output from the cycle detection unit, a signal obtained by masking the rotation reference signal with the mask signal generated by the signal generation unit is output, and the mask detection signal is output from the cycle detection unit. When is output, a signal output unit that outputs a signal that is not masked by the mask signal generated by the signal generation unit, the rotation reference signal,
A motor control unit that controls the rotation control unit of the optical scanning device based on the signal output from the signal output unit to accelerate or decelerate the motor;
Have
The cycle detection unit outputs the mask permission signal when the cycle of the rotation reference signal is within a predetermined range, and prohibits the mask when the cycle of the rotation reference signal is outside the predetermined range. An image forming apparatus that outputs a signal. The image forming apparatus according to claim 1, wherein the motor outputs the rotation reference signal according to a rotation cycle of the motor. The optical scanning device has a detection means for detecting the light beam deflected by the rotary polygon mirror,
The image forming apparatus according to claim 2, wherein the detection unit outputs the rotation reference signal when detecting the light beam. The said period detection part detects the period of the said rotation reference signal based on the rotation reference signal output from the said motor, or the rotation reference signal output from the said detection means, The said 3rd aspect is characterized by the above-mentioned. Image forming device. The image forming apparatus according to claim 4, wherein the mask signal has a mask period for masking a predetermined period of one cycle of the rotation reference signal. The said predetermined range of the period of the said rotation reference signal is longer than the said mask period, and is shorter than the period which added the margin part to the predetermined period of the said rotation reference signal, It is characterized by the above-mentioned. Image forming device. The image according to claim 6, wherein the cycle detection unit outputs the mask permission signal or the mask prohibition signal according to the cycle of the rotation reference signal, for each cycle of the rotation reference signal. Forming equipment. The cycle detection unit outputs the mask permission signal when the cycle in which the cycle of the rotation reference signal is within the predetermined range continues for a predetermined period or more, and the cycle of the rotation reference signal is within the predetermined range. 7. The image forming apparatus according to claim 6, wherein the masking prohibition signal is output when the certain cycle does not continue for a predetermined period or longer. The motor control unit detects the rotation state of the motor based on the signal output from the signal output unit, and when the motor control unit detects that the motor is rotating at a predetermined speed, the motor control unit Outputs a status signal indicating that it is rotating stably,
When the state signal is not output from the motor control unit, the signal output unit outputs a signal in which the rotation reference signal is not masked by the mask signal generated by the signal generation unit. The image forming apparatus according to claim 8. A control means for controlling image formation on the recording medium,
10. The control unit detects an abnormality of the motor based on the state signal output from the motor control unit and the mask inhibition signal output from the cycle detection unit. The image forming apparatus according to item 1. Equipped with a display unit that displays information,
The image forming apparatus according to claim 10, wherein, when the control unit detects an abnormality of the motor, the control unit displays alarm information for notifying the abnormality of the motor on the display unit. The motor control unit accelerates the rotation speed of the motor when the cycle of the signal output from the signal output unit is longer than a predetermined cycle, and the cycle of the signal output from the signal output unit is 12. The rotation control unit of the optical scanning device is controlled so as to reduce the rotation speed of the motor when the cycle is shorter than a predetermined cycle, according to any one of claims 1 to 11. The image forming apparatus described.

Images