JP2019070702A - Scanner and image forming apparatus - Google Patents

Abstract

To solve the problem in which: when a plurality of laser elements forcibly irradiate a photoconductor drum with light at the start-up of a scanner, the photoconductor drum may be deteriorated.SOLUTION: In a start-up period for controlling a rotation speed such that a rotary polygon mirror rotates at a predetermined rotation speed, control means controls a first light emitting unit to execute first light emission of causing a scanner to scan an image area and a non-image area with light emitted from the first light emitting unit, and when detection means detects light at least twice in a period during which the first light emitting unit executes the first light emission, controls the first light emitting unit to execute second light emission of causing the scanner to scan the non-image area with the light emitted from the first light emitting unit, and controls a second light emitting unit to execute third light emission of causing the scanner to scan the non-image area with light emitted from the second light emitting unit.SELECTED DRAWING: Figure 5

Description

  The present invention relates to start control of a scanning device used in an image forming apparatus such as an electrophotographic printer that performs exposure with laser light.

  Conventionally, in an electrophotographic image forming apparatus, as described in Patent Document 1, the start-up control of the scanner motor causes the laser to emit light for a predetermined time while forcibly rotating the scanner motor, and the laser light scanned by the polygon mirror Is detected by the detection means. Then, the number of rotations of the scanner motor is determined based on the period of the detection signal, it is determined whether or not the predetermined number of rotations has been reached, and if the number of rotations has not reached the predetermined number of rotations After that, the control was repeated to obtain the number of revolutions.

Japanese Patent Application Publication No. 08-002001

  However, the speed of the image forming apparatus tends to be increased by a scanning device provided with a plurality of laser elements in recent years, as well as a scanning device provided with a single laser element as in Patent Document 1. At the time of starting of such a scanning device, there is a possibility that the photosensitive drum may be deteriorated if the plurality of laser elements forcibly emit light on the photosensitive drum.

  The invention according to the present application is made in view of the above situation, and has an object of performing start control of a scanning device that suppresses deterioration of a photosensitive drum.

  In order to achieve the above object, there is provided an illumination unit having a first light emitting unit and a second light emitting unit, and a light capable of reflecting light emitted from the illumination unit and capable of scanning an image area and a non-image area on a photosensitive member. In a scanning device comprising: a polygon mirror; detection means for detecting light reflected by the rotary polygon mirror; and control means for controlling light emission of the first light emitting unit and the second light emitting unit; A first period in which the image area and the non-image area are scanned by the light emitted from the first light emitting unit during a start-up period in which the rotational speed is controlled such that the rotary polygon mirror rotates at a predetermined rotational speed. Control the first light emitting unit to emit light, and the first light emitting unit detects light at least twice by the detection unit while the first light emitting unit is performing the first light emission It is emitted from the part The first light emitting unit is controlled to be a second light emission causing the light to scan the non-image area, and the light emitted from the second light emitting unit is caused to scan the non-image area The second light emitting unit is controlled to emit light.

  According to the present invention, it is possible to perform start control of the scanning device that suppresses the deterioration of the photosensitive drum.

Schematic configuration of the image forming apparatus The perspective view which shows schematic structure of the scanning device 111 and the laser scanner unit 112 which is the principal part Configuration diagram of the laser drive circuit 113 Configuration diagram of APC circuit Characteristic chart showing the change in the number of revolutions from the start of scanner motor start Timing chart of signals related to start control of scanning device Flowchart showing start control of the scanning device 111 Timing chart of signals related to start control of the scanning device 111 Timing chart of signals related to start control of scanning device Configuration diagram of the laser drive circuit 113 Timing chart of signals related to start control of the scanning device 111 A characteristic diagram showing a change in rotational speed when a restart instruction is received after the scanner motor 103 is instructed to stop. A diagram showing the relationship between the elapsed stop time Ts and the light emission start time T1 Flowchart showing start control of the scanning device 111

  Hereinafter, embodiments of the present invention will be described using the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of the features described in the embodiments are not necessarily essential to the solution means of the invention.

First Embodiment
[Image forming apparatus]
FIG. 1 is a cross-sectional view showing a schematic configuration of the image forming apparatus 100. As shown in FIG. The image forming apparatus 100 employs an intermediate transfer method, and four process units 5Y, 5M, 5C, and 5K are arranged in series along the rotational direction of the intermediate transfer belt 8 as an intermediate transfer member. . Here, the intermediate transfer belt 8 is configured of an endless belt. In each of the process units 5Y, 5M, 5C and 5K, printing operation (image formation using toner (developer) of different colors of yellow (Y), magenta (M), cyan (C) and black (K) Operation) is performed.

  In the image forming apparatus 100, a scanning device 111 is a scanning unit that emits laser light to the photosensitive drums 1Y, 1M, 1C, and 1K, which are photosensitive members provided in the respective process units 5Y, 5M, 5C, and 5K. Is provided. By irradiating light from the scanning device 111, an electrostatic latent image is formed on the photosensitive member. Further, in the image forming apparatus 100, a CPU 110 for controlling the operation of each unit and an image controller 300 are provided. The image controller 300 is electrically connected to the scanning device 111, and forms an image by the modulated laser light based on the image signal (image signal VDO) sent from the image controller 300.

  The scanning device 111 is provided with semiconductor lasers 101Y, 101M, 101C, and 101K as light emitting units, a polygon mirror 102, a scanner motor 103, and folding mirrors 104Y, 104M, 104C, and 104K. Here, the semiconductor lasers 101Y, 101M, 101C, and 101K correspond to light sources for emitting (emitting) laser light. The polygon mirror 102 corresponds to a polygon mirror that reflects (deflects and scans) light emitted from the semiconductor lasers 101Y, 101M, 101C, and 101K.

  Laser light emitted from the semiconductor lasers 101Y, 101M, 101C, and 101K is reflected by the rotating polygon mirror 102, and is returned by the return mirrors 104Y, 104M, 104C, and 104K. Then, the folded laser beam is configured to be irradiated (imaged) onto the photosensitive drums 1Y, 1M, 1C, and 1K. As described above, the light is reflected by the rotating polygon mirror 102 so that the photosensitive drum 1 can be scanned. The scanner motor 103 is connected to the polygon mirror 102, and as the scanner motor 103 rotates, the polygon mirror 102 rotates.

  As described above, the image forming apparatus 100 configures an image forming unit (station) that forms an image on the photosensitive drums 1Y, 1M, 1C, and 1K for each toner color. Each station has process units 5Y, 5M, 5C, 5K in which photosensitive drums 1Y, 1M, 1C, 1K are disposed, lasers 101Y, 101M, 101C, 101K, folding mirrors 104Y, 104M, 104C, 104K. There is. The polygon mirror 102 and the scanner motor 103 are common to each station in the present embodiment and are configured by one, but may be two or more.

  Next, an image forming operation (printing operation) of the image forming apparatus will be described. Here, the configuration and operation of each process unit are substantially the same except that the color of the toner used is different. Therefore, in the following description, the suffixes Y, M, C, and K given to the reference numerals in FIG. 1 will be collectively described in the case where distinction is not particularly required.

  Each process unit 5 is provided with a photosensitive drum 1 to which laser light is irradiated, and a charging roller 2 that charges the photosensitive drum 1. Further, among the charged photosensitive drum 1 surface, a developing roller 3 is provided as a developing member for developing the electrostatic latent image formed by irradiating the laser light by the scanning device 111 with the toner 23 attached. It is done.

  In the process unit 5, the distance between the developing roller 3 and the photosensitive drum 1 is regulated by a cam (not shown). And, by changing the distance between the developing roller 3 and the photosensitive drum 1 by rotating the cam, the developing position where the developing roller 3 can contact the photosensitive drum 1 and can perform the developing operation, It is configured to be movable between the developing position and the separated position retracted. The switching between the development position and the retracted separation position can be performed by turning on and off the development solenoid 31 as the moving means in accordance with a control signal from the CPU 110. The moving means is not limited to the developing solenoid 31.

  In addition, primary transfer rollers 6 are disposed at positions facing the respective photosensitive drums 1 with the intermediate transfer belt 8 interposed therebetween. By applying a bias to the primary transfer roller 6, a primary transfer portion is formed between the photosensitive drum 1 and the intermediate transfer belt 8, and the toner 23 on the photosensitive drum 1 is sequentially applied to the intermediate transfer belt 8. Primary transfer.

  When the start-up rotation of the scanner motor 103 is started, the recording material P is picked up by the pickup roller 14 and feeding of the recording material P is started. At this time, the recording material P is fed to a secondary transfer portion formed between the intermediate transfer belt 8 and the secondary transfer roller 11. The toner image primarily transferred onto the intermediate transfer belt 8 is secondarily transferred onto the recording material P at the secondary transfer portion, and the recording material P onto which the toner image has been transferred is heated and pressed by the fixing device 52. Thus, the toner image is fixed to the recording material P. The fixed recording material P is discharged to the discharge tray 53, and the printing operation is completed.

  FIG. 2 is a perspective view showing a schematic configuration of the scanning device 111 and the laser scanner unit 112 which is the main part thereof. The configuration and operation of the scanning device 111 are substantially the same except that the color of the toner that is the object of image formation is different. Therefore, in the following description, the suffixes Y, M, C, and K given to the reference numerals in FIG. 1 will be collectively described in the case where distinction is not particularly required. The semiconductor laser 101 includes four laser diodes (a laser 101 a, b laser 101 b, c laser 101 c, d laser 101 d) which are laser elements, and one photodiode 120, and the light emission control is performed by the laser drive circuit 113. Be done. A detailed description of the control operation of the semiconductor laser 101 by the laser drive circuit 113 will be described later. The scanner motor 103 is an example of a drive unit that rotates the polygon mirror 102 that is a rotary polygon mirror, and rotates the polygon mirror 102 in the illustrated rotation direction.

  The laser beam reflected by the rotational movement of the polygon mirror 102 is periodically scanned with respect to the entire scanning area 116 formed in the laser scanner unit 112. The entire scanning area 116 is divided into an image area 114 and a non-image area 115, and the image area 114 irradiates the surface of the photosensitive drum 1 through the folding mirror 104 among the laser light reflected by the polygon mirror 102. Point to the area to be On the other hand, the non-image area 115 refers to an area of the entire scanning area 116 excluding the image area 114.

  A BD (Beam Detect) sensor 106 provided in a predetermined area in the non-image area 115 generates a horizontal synchronization signal 107 as a signal corresponding to the laser light in response to the incidence of the laser light. The horizontal synchronization signal 107 is hereinafter also referred to as a BD (Beam Detect) signal 107. The cycle in which the BD signal 107 is generated is called a BD cycle. The BD signal 107 is used as a scanning start reference signal in the main scanning direction, and is used to control the writing start position in the main scanning direction.

  The CPU 110, which is a control unit, updates the BD cycle each time the BD signal 107 is generated, and stores the BD cycle in the memory 117, which is a storage unit. Then, based on the BD cycle stored in the memory 117, the scanner motor 103 and the semiconductor laser 101 are controlled. That is, the CPU 110 transmits the scanner motor drive signal 108 to the scanner motor 103. The scanner motor 103 is targeted by transmitting a signal to accelerate when the number of revolutions corresponding to the current BD cycle is smaller than the set target number of revolutions, and a signal to decelerate when the number of revolutions is large. Speed control is performed to converge on the rotational speed. Further, the CPU 110 transmits a laser drive signal 109 to the laser drive circuit 113, and performs light emission control so that the semiconductor laser 101 emits light at a predetermined timing in the entire scanning region 116.

  Next, the control operation of the laser drive circuit 113 will be described using FIG. 3 and FIG. FIG. 3 is a block diagram of the laser drive circuit 113. As shown in FIG. The laser drive circuit 113 performs APC (Auto Power Control) to stabilize the laser light amount of the semiconductor laser 101. As circuits for performing the APC, an a-laser APC circuit 200a, a b-laser APC circuit 200b, a c-laser APC circuit 200c, and a d-laser APC circuit 200d are provided. Each APC circuit is connected to a laser diode (a laser 101a, b laser 101b, c laser 101c, d laser 101d) constituting the semiconductor laser 101, a photodiode 120, and a laser drive signal 109 sent from the CPU 110. .

  Next, the APC operation of the a laser 101a will be described using the a laser APC circuit 200a. FIG. 4 is a block diagram of the a-laser APC circuit 200a. The configurations of the b-laser APC circuit 200b, the c-laser APC circuit 200c, and the d-laser APC circuit 200d are the same, and therefore, the a-laser APC circuit 200a is illustrated and described here.

  The photodiode 120 is an element that monitors the light quantity of the a laser 101a, and outputs a current substantially proportional to the light quantity of the a laser 101a, and the resistor 201 converts the current into a voltage. The voltage 202 converted by the resistor 201 is input to the comparator 204. That is, the voltage 202 proportional to the light amount of the a laser 101 a is input to one input terminal of the comparator 204. The reference voltage 205 output from the reference voltage generator 203 is input to the other input terminal of the comparator 204. The comparator 204 compares the voltage 202 with the reference voltage 205, and outputs the result to the sample and hold unit 206.

  The sample and hold unit 206 turns on and off the transistor 209 and the transistor 210 in accordance with the sample and hold timing signal 208 output from the decode unit 207 and the output of the comparator 204. Here, the decoding unit 207 decodes the laser drive signal 109 and outputs a sample hold timing signal 208 and a light emission control signal 215. When sampling is performed, the a-laser 101a is made to emit light, and the decoding unit 207 notifies the sample-and-hold unit 206 of the timing of the sample using the sample-and-hold timing signal 208.

  If the reference voltage 205 is higher than the voltage 202 which is proportional to the amount of laser light, the sample hold unit 206 turns on the transistor 209 and turns off the transistor 210 to raise the voltage 212 applied to the hold capacitor 211. Conversely, if the reference voltage 205 is lower than the voltage 202 which is proportional to the laser light quantity, the transistor 212 is turned off and the transistor 210 is turned on to lower the voltage 212 applied to the hold capacitor 211. The voltage 212 applied to the hold capacitor 211 is buffered by the buffer 213 to control the current of the constant current source 214. As the voltage 212 applied to the hold capacitor 211 increases, the current flowing to the a laser 101 a increases in proportion to the voltage 212. Further, the constant current source 214 turns on / off the current flowing to the a laser 101 a by the light emission control signal 215 output from the decoding unit 207.

  By the above operation, the light quantity of the a laser 101a is adjusted to the light quantity determined by the reference voltage 205 and the resistance value of the resistor 201 that generates the voltage 202 proportional to the light quantity of the a laser 101a. In the hold state, the sample hold unit 206 turns off both the transistor 209 and the transistor 210 to hold the voltage 212 applied to the hold capacitor 211 and keep the amount of light of the a laser 101 a constant. The same operation as the control described above is performed on the b laser 101 b, the c laser 101 c, and the d laser 101 d as well as the b laser APC circuit 200 b, the c laser APC circuit 200 c, and the d laser APC circuit 200 d.

  However, in the present embodiment, because of the configuration in which one photodiode 120 is provided for four laser diodes, APCs of four laser diodes are exclusively executed at independent timings for the respective lasers. Since there is only one photodiode 120 which is a common light receiving means, when light is emitted simultaneously from a plurality of lasers, the output of the photodiode 120 is the sum of the light amounts of the plurality of lasers. In this case, since the appropriate APC can not be performed by each laser, the timing of the APC is controlled so as not to be overlapped by a plurality of lasers.

  Next, control at the time of activation of the scanning device 111 will be described. FIG. 5 is a characteristic diagram showing a change in the number of rotations from the start of the scanner motor 103. The horizontal axis represents time, and the vertical axis represents the number of rotations of the scanner motor 103. Further, the control states of the scanner motor 103 controlled by the CPU 110, the a laser 101a, the b laser 101b, the c laser 101c, and the d laser 101d are also described. FIG. 6 is a timing chart of signals related to start control of the scanning device 111. As shown in FIG. The light emission state of the BD signal 107, the a laser 101a, the b laser 101b, the c laser 101c, and the d laser 101d is shown. The BD signal 107 is a signal which becomes H level when the BD sensor 106 does not receive the laser light, and L level when the laser light is received, and the light emission state of each laser is L level of the unlit state, laser It is a signal that sets the state in which APC is performed by emitting light to the H level.

  When a print start instruction is issued, the CPU 110 starts activation control of the scanner motor 103 according to the scanner motor drive signal 108 at a predetermined timing after the print start instruction is generated. The scanner motor 103 operates according to a target rotation number which is a set predetermined rotation number and a speed control instruction from the CPU 110, and the polygon mirror 102 also starts to rotate with the rotation of the scanner motor 103. At this time, since all the lasers are turned off and the BD signal 107 is not generated, the scanner motor 103 is instructed to accelerate (t301). That is, the period from when the start control is started to when the polygon mirror 102 reaches the target rotation speed can also be called a start-up period of the polygon mirror 102.

  At a first timing (t302) at which a predetermined time has elapsed since the start of activation of the scanner motor 103, the CPU 110 emits the a laser 101a, which is the reference laser, of the semiconductor laser 101 over the entire scanning region 116 (first Light emission) (t303). Immediately after the scanner motor 103 is activated, the number of rotations of the scanner motor 103 is small and the scanning speed of the polygon mirror 102 is also slow. Therefore, the energy in the case where the photosensitive drum 1 is irradiated with the laser beam is larger than the energy in the case where the polygon mirror is rotating at a high scanning speed for forming an ordinary image, and the deterioration of the photosensitive drum 1 is promoted. there is a possibility. Therefore, from the start of start of the scanner motor 103 (t301) to the first timing (t302), all the lasers are turned off so that the photosensitive drum 1 is not exposed. Then, after the scanner motor 103 is in a stable acceleration state, the light emission of the a laser 101a is started, thereby suppressing the unnecessary deterioration of the photosensitive drum 1.

  The a laser 101a performs APC by emitting the first light. When the laser light amount of the a laser 101a is increased by the APC, the BD signal 107 corresponding to the laser light periodically received by the BD sensor 106 starts to be generated. As shown in FIG. 6, when the BD signal 107 is generated twice by the first light emission by the a laser 101a, that is, when light is detected twice by the BD sensor 106, the BD cycle P1 is generated from the two BD signals 107. Desired. The determined BD cycle P1 is stored in the memory 117 as a storage unit.

  When the BD cycle P1 is determined, the second timing at which the second BD signal 107 is generated (the CPU 110 controls to cause all the lasers to emit light in the non-image area 115 (hereinafter also referred to as unblanking control)) Unblanking control is started from t304) onward. First, control of the a laser 101a will be described. At the second timing (t304), the CPU 110 calculates a value P1 × Ma [%] obtained by multiplying the BD cycle P1 updated most recently by the setting value Ma preset for the a laser 101a. . Then, light emission (second light emission) of the a laser 101a is performed to obtain the next BD signal 107 at the timing when P1 × Ma [%] has elapsed from the timing when the BD signal is acquired. Since this light emission is unblanking control, it is performed in the non-image area 115, and when the laser light is received by the BD sensor 106, the next BD signal 107 is acquired. When the BD signal is acquired, the a-laser 101a is stopped so as not to emit light in the image area 114 (t305).

  The second light emission is performed while sequentially determining the light emission timing as the stored BD cycles P1, P2, P3,..., Pn are updated. Here, since the speed control of the scanner motor 103 is accelerating toward the target rotation speed, the BD cycle tends to be gradually shortened, but the change rate of adjacent BD cycles is small. Therefore, by determining the light emission timing at the time of the next scan from the BD cycle information stored last time, unblanking control is realized that emits light in the non-image area 115 and acquires the next BD signal 107. That is, the setting value Ma is set based on the timing at which the non-image area 115 and the next BD signal 107 are acquired. As shown in FIG. 6, by emitting the a laser 101a at the light emission timing determined by P1 × Ma, P2 × Ma, P3 × Ma,..., Pn × Ma, light is emitted in the non-image area 115, and It is realized that the next BD signal 107 is acquired. Although the switching to the unblanking control from the timing at which the BD signal is acquired twice is described here as an example, the present invention is not limited to this. Of course, if it is twice or more, it may be switched from the BD signal to the unblanking control at any time, but switching to the unblanking control at the time when it can be acquired twice is good for suppressing deterioration of the photosensitive drum 1 .

  When the scanner motor 103 reaches 1% or less of the target rotational speed (t306), the CPU 110 determines that the rising of the scanner motor 103 is completed. The laser light amount of the a laser 101a is adjusted and stabilized to a desired light amount suitable for image formation by being APC during unblanking control for acquiring the BD signal 107.

  Next, control of the b laser 101 b will be described. At the second timing (t304), the CPU 110 calculates a value P1 × Mbs [%] obtained by multiplying the BD cycle P1 updated most recently by the setting value Mbs preset for the b laser 101b. . Then, the light emission (third light emission) of the b-laser 101b is performed at the timing when P1 × Mbs [%] has elapsed from the timing when the BD signal is acquired. Moreover, similarly to the light emission start timing, the light emission end timing calculates a value P1 × Mbe [%] obtained by multiplying the BD cycle P1 updated most recently by a preset setting value Mbe. Then, the b-laser 101 b is stopped so as not to emit light in the image area 114 at a timing when P1 × Mbe [%] has elapsed since the timing when the BD signal was acquired.

  The third light emission is performed while sequentially determining the light emission timing as the stored BD cycles P1, P2, P3,..., Pn are updated. The setting values Mbs and Mbe are set so that the b laser 101 b emits light in the non-image area 115. As shown in FIG. 6, by emitting the b-laser 101b at the light emission timing determined by P1 × Mbs, P1 × Mbe,... Pn × Mbs, Pn × Mbe, light is emitted in the non-image area 115 It is done. As for the c-laser 101c and the d-laser 101d, similarly to the b-laser 101b, the C-laser 101c emits a fourth light and the d-laser 101d emits a fifth light (t305). That is, the setting values Mbs of the b laser 101b, the setting values Mcs and Mce corresponding to Mbe, and the setting values Mds and Mde are set for the c laser 101c and the d laser 101d, respectively.

  When the scanner motor 103 reaches 1% or less of the target rotational speed (t306), the CPU 110 determines that the rising of the scanner motor 103 is completed. The amount of light of the b laser 101 b, c laser 101 c, and d laser 101 d is adjusted and stabilized to a desired amount of laser light suitable for image formation by APC during unblanking control of each laser.

  As described above, the start control of the scanner motor 103 is performed while the unblanking control of emitting light in the non-image area 115 is performed at the second timing (t304) and after, on all the lasers. In the present embodiment, only one photodiode 120 is provided for four laser diodes. Therefore, as shown in FIG. 6, the light emission timings of the respective lasers are exclusively executed at independent timings so as not to overlap with the light emission timings of the other lasers. Furthermore, as shown in FIG. 6, in the present embodiment, all four lasers are controlled to emit light in a non-image area 115 period during one cycle (1 BD cycle) of the BD signal. Here, as an example, the a laser 101a emits light in a period for detecting a BD signal. The b laser 101 b and the c laser 101 c emit light in a period of the non-image area 115 from detection of the BD signal to the image area 114. The d-laser 101d emits light in a period of the non-image area 115 until the next BD signal is detected after the image area 114 passes. By controlling in this way, APC of all lasers can be performed during one BD cycle.

  FIG. 7 is a flowchart showing start control of the scanning device 111. In step S301, the CPU 110 starts activation of the scanner motor 103. In step S302, the CPU 110 determines whether a predetermined time has elapsed since the scanner motor 103 was started. When the predetermined time has elapsed, the CPU 110 causes the a laser 101a to emit light in the entire scanning region 116 in S303.

  In S304, the CPU 110 determines whether the BD signal 107 has been acquired twice. If the BD signal is acquired twice, the CPU 110 sets the a-laser 101a as the second light emission to emit light in the non-image area 115 in S305. Further, the b laser 101 b, the c laser 101 c, and the d laser 101 d are set as the third light emission in the non-image area 115. In step S306, the CPU 110 determines whether the scanner motor 103 has reached the target rotation number. When the target rotation number is reached, the CPU 110 determines that the rising of the scanner motor 103 is completed in S307.

  As described above, when the scanning device 111 is activated, the irradiation of the laser beam to the photosensitive drum 1 can be suppressed to the period in which the first light emission is performed. Therefore, even in the configuration having a plurality of laser diodes, deterioration of the photosensitive drum 1 can be suppressed by not unnecessarily increasing the time for which the photosensitive drum 1 is irradiated with the laser light. Also, after the second timing, all laser diodes are controlled to emit light in the non-image area 115 to perform APC. As a result, the light amount of each semiconductor laser can be adjusted and stabilized using the period until the start-up of the scanner motor 103 is completed. Therefore, since it is not necessary to separately provide a period for APC, it is possible to shorten the first print out time (FPOT) which is the time until the first image is formed.

Second Embodiment
In the first embodiment, the method of performing APC of all the lasers in one BD cycle has been described. In the present embodiment, a control method will be described in which a laser performing APC during one BD cycle is different from that of the first embodiment. The detailed description of the same configuration as that of the first embodiment such as the above-described image forming apparatus and scanning device will be omitted here.

  FIG. 8 is a timing chart of signals related to start control of the scanning device 111. As shown in FIG. First, at the second timing, of the b laser 101 b, the c laser 101 c, and the d laser 101 d, only the b laser 101 b emits light in the non-image area 115. At this time, the b-laser 101b calculates a value P1 × Mbs1 [%] obtained by multiplying the BD cycle P1 updated most recently by the preset setting value Mbs1. Then, the light emission (third light emission) of the b laser 101b is performed at the timing when P1 × Mbs1 [%] has elapsed from the timing when the BD signal is acquired. Further, similarly to the light emission start timing, the light emission end timing calculates a value P1 × Mbe1 [%] obtained by multiplying the BD cycle P1 updated most recently by a preset setting value Mbe1. Then, the b-laser 101 b is stopped so as not to emit light in the image area 114 at a timing when P1 × Mbe1 [%] has elapsed from the timing when the BD signal is acquired. Similarly, a set value Mbs 2 and a set value Mbe 2 for performing a third light emission after the image area 114 are also set, and light is emitted also in a period obtained from these set values.

  As described above, in one certain BD cycle, control is performed to cause the a-laser 101a and the b-laser 101b to emit light in the non-image area 115 for detecting a BD signal. Then, each time the BD cycle is updated, APC of the b laser 101b is performed, and when the light quantity of the b laser 101b is adjusted to near the target light quantity, the c laser 101c is not imaged from the next BD cycle (BD cycle P2) It switches to the control made to emit light at 115. That is, similarly to the control of the b laser 101b, light is emitted in the non-image area 115 based on the value calculated according to the BD cycle updated most recently and the setting values Mcs1, Mce1, Mcs2, and Mce2, and APC is performed. Then, when the light amount of the c-laser 101c is adjusted to near the target light amount, control is switched to control to cause the d-laser 101d to emit light in the non-image area 115 from the next BD cycle (BD cycle P3). That is, APC is performed by emitting light in the non-image area 115 based on the BD cycle updated most recently and the values calculated according to the setting values Mds1, Mde1, Mds2, and Mde2.

  As described above, after all the lasers are adjusted close to the target light amount, for example, all the lasers may be switched to perform APC during one BD cycle after the timing when the BD cycle becomes P4. Further, as shown in FIG. 9, when the scanner motor 103 reaches the target rotation speed and the BD cycle becomes shorter than at the time of start-up, it may not be possible to intensively acquire the APC period of each laser. In such a case, control may be periodically switched to execute light emission of each laser in the non-image area 115 once in one BD cycle. That is, when the BD cycle is Pn2, the control of the light emission of the b laser 101b, the light emission of the c laser 101c when the BD cycle is Pn3, and the light emission of the d laser 101d when the BD cycle is Pn4 is repeatedly executed.

  As described above, by appropriately changing the laser that performs the third light emission in the non-image area 115 during the start control of the scanner motor 103, it is possible to efficiently APC all the laser diodes. Each APC circuit of the laser drive circuit 113 is configured to hold the light amount of each laser by holding the voltage 212 applied to the hold capacitor 211. The voltage 212 applied to the hold capacitor 211 may gradually change due to the leak current of the transistors 209 and 210 in the hold state, and a sufficient time is ensured until the target light amount is adjusted and stabilized. And need to do APC. Therefore, by performing the APC for a certain fixed period, a sufficient APC time can be secured, and each laser can be efficiently adjusted to the target light amount and stabilized.

Third Embodiment
In the above first embodiment, the configuration having one photodiode for four laser diodes has been described. In the present embodiment, a configuration having four photodiodes, one for each of the four laser diodes, will be described. The detailed description of the same configuration as that of the first embodiment such as the above-described image forming apparatus and scanning device will be omitted here.

  FIG. 10 is a block diagram of the laser drive circuit 113 in the present embodiment. Similar to FIG. 3, each APC circuit is connected to the laser diode (a laser 101a, b laser 101b, c laser 101c, d laser 101d) constituting the semiconductor laser 101, and the laser drive signal 109 sent from the CPU 110 It is done. In the laser drive circuit 113 of the present embodiment, one photodiode (120a, 120b, 120c, 120d) is provided for each of the laser diodes (a laser 101a, b laser 101b, c laser 101c, d laser 101d). Is equipped.

  FIG. 11 is a timing chart of signals related to start control of the scanning device 111 in the present embodiment. With the configuration of the laser drive circuit 113 in the present embodiment, the third light emission can be simultaneously performed by the b laser 101 b, the c laser 101 c, and the d laser 101 d. That is, at the second timing, the b laser 101b, the c laser 101c, and the d laser 101d have a value P1 × Ms1 [% obtained by multiplying the BD cycle P1 updated most recently by the preset value Ms1. Calculate]. Then, light emission (third light emission) of the b-laser 101b, the c-laser 101c, and the d-laser 101d is performed at a timing when P1 × Ms1 [%] has elapsed from the timing when the BD signal is acquired. Further, similarly to the light emission start timing, the light emission end timing calculates a value P1 × Me1 [%] obtained by multiplying the BD cycle P1 updated most recently by a preset setting value Me1. Then, the light emission of the b laser 101 b, the c laser 101 c, and the d laser 101 d is stopped at the timing when P1 × Me1 [%] has elapsed from the timing when the BD signal is acquired. Similarly, the setting value Ms2 and the setting value Me2 for performing the third light emission after the image area 114 are also set, and the light emission is performed also in the period obtained from these setting values. Light is emitted in such a non-image area 115, and APC is performed for each of the b laser 101b, the laser 101c, and the d laser 101d.

  Although FIG. 11 shows control for causing all of the b laser 101b, the laser 101c, and the d laser 101d to emit light at the same timing, the emission timings of the non-image areas 115 may be different. Further, in FIG. 11, in a period in which the a laser 101a which is the reference laser emits light to acquire the BD signal 107, control is performed such that the lasers other than the a laser 101a do not emit light. This is to prevent the occurrence of an error in the timing of acquiring the BD signal 107 when the lasers other than the a laser 101 a emit light. The generation timing of the BD signal 107 is used as a writing start position in the main scanning direction. In order to enhance the quality of image formation, it is desirable to emit only the reference laser a 101 a responsible for emitting the BD signal 107 at the generation timing of the BD signal 107. However, if the configuration of the scanning device 111 is such that the laser light does not enter the BD sensor 106 even if the laser other than the a laser 101 a emits light in any region of the entire scanning region 116, the a laser 101 a and other lasers The light emission timing may be superimposed.

  As described above, by controlling the periods of the third light emission of the plurality of laser diodes so as to overlap, the light emission period of the non-image area 115 of each laser diode can be extended. As a result, APC of each laser can be efficiently performed, and the target light amount can be adjusted and stabilized.

Fourth Embodiment
In the first embodiment, the control for starting from the state where the scanner motor 103 is stopped has been described. In the present embodiment, a case where the scanner motor 103 is restarted before being stopped will be described. The detailed description of the same configuration as that of the first embodiment such as the above-described image forming apparatus and scanning device will be omitted here.

  FIG. 12 is a characteristic diagram showing a change in rotational speed when a restart instruction is received after the scanner motor 103 is instructed to stop. The horizontal axis represents time, and the vertical axis represents the rotational speed of the scanner motor 103. Further, the control states of the scanner motor 103 controlled by the CPU 110, the a laser 101a, the b laser 101b, the c laser 101c, and the d laser 101d are also described.

  When the printing operation is completed, the CPU 110 turns off all the lasers, instructs the scanner motor 103 to stop, and starts measuring the elapsed stop time Ts (t400). As time passes, the number of rotations of the scanner motor 103 gradually decreases toward the stop state.

  Next, before the scanner motor 103 is stopped, when the print start is instructed (t 401), the CPU 110 instructs the scanner motor 103 to restart. As in the first embodiment, all the lasers are turned off until the first timing, and the BD signal 107 is not generated. Thus, the scanner motor 103 is forced to accelerate. If the predetermined time until the first timing is determined to be fixed, if the time from the stop instruction of the scanner motor 103 to the restart instruction is extremely short, the target rotation speed is exceeded and overshooting occurs. There is a possibility of As a result, it takes extra time to adjust the overshoot, which may delay the time to reach the target rotation speed.

  Therefore, in the present embodiment, when the scanner motor 103 is instructed to restart, the measurement of the elapsed stop time Ts of the scanner motor 103 is ended. Then, based on the obtained value of the stop elapsed time Ts, the light emission start time T1 until the start of the first timing is determined (t401). FIG. 13 is a diagram showing the relationship between the elapsed stop time Ts and the light emission start time T1. The CPU 110 calculates the light emission start time T1, which is a value proportional to the value of the stop elapsed time Ts, and determines the first light emission timing (t402). If the value of the stop elapsed time Ts is equal to or larger than the sufficiently large value Tsmax, the CPU 110 determines that the restart instruction is from the state where the scanner motor 103 is stopped, and the light emission start time T1 is a predetermined maximum value T1max. Only secure. On the other hand, if the value of the stop elapsed time Ts is equal to or less than the predetermined elapsed time Ts0, the CPU 110 determines that the scanner motor 103 is a restart instruction at a relatively early timing from the stop instruction, and secures the light emission start time T1. do not do.

  The CPU 110 causes the a laser 101a, which is the reference laser, of the semiconductor laser 101 to emit light (first light emission) over the entire scanning region 116 at the timing based on the determined light emission start time T1 (t403). The subsequent control method is the same as that of the first embodiment described above. The CPU 110 starts unblanking control after the second timing (t 404) at which the BD signal 107 is generated twice so as to perform unblanking control of causing all lasers to emit light in the non-image area 115. That is, the a laser 101a starts the second light emission, the b laser 101b starts the third light emission, the c laser 101 c starts the fourth light emission, and the d laser 101 d starts the fifth light emission (t405).

  Then, when the scanner motor 103 reaches 1% or less of the target rotation speed (t406), the CPU 110 determines that the rising of the scanner motor 103 is completed. The amount of light of all the lasers is adjusted and stabilized to a desired amount of light suitable for image formation by being APC during unblanking control.

  FIG. 14 is a flowchart showing activation control of the scanning device 111. In S400, the CPU 110 turns off the laser diode and stops the scanner motor 103. Further, the stop elapsed time Ts, which is the elapsed time after the scanner motor 103 is stopped, is measured. In step S401, the CPU 110 starts to restart the scanner motor 103. Then, the measurement of the elapsed stop time Ts is ended. In step S402, the CPU 110 obtains a predetermined time based on the stop elapsed time Ts, and determines whether the predetermined time has elapsed since the start of the scanner motor 103. When the predetermined time has elapsed, the CPU 110 causes the a laser 101a to emit light in the entire scanning region 116 in S403.

  In S404, the CPU 110 determines whether the BD signal 107 has been acquired twice. If the BD signal is acquired twice, the CPU 110 sets the a-laser 101a as the second light emission to emit light in the non-image area 115 in S405. Further, the b laser 101 b, the c laser 101 c, and the d laser 101 d are set as the third light emission in the non-image area 115. In S406, the CPU 110 determines whether the scanner motor 103 has reached the target rotation number. When the target rotational speed is reached, the CPU 110 determines in S <b> 407 that the rising of the scanner motor 103 is completed.

  As described above, even when the scanner motor 103 is restarted before the scanner motor 103 stops, control is performed to cause the scanner motor 103 to reach the target rotation number without causing overshoot that deviates from the target rotation number. be able to. Also, after the second timing, all laser diodes are controlled to emit light in the non-image area 115 to perform APC. As a result, the light amount of each semiconductor laser can be adjusted and stabilized using the period until the start-up of the scanner motor 103 is completed.

102 polygon mirror 106 BD sensor 110 CPU
111 Scanner

Claims (16)

An irradiation unit having a first light emitting unit and a second light emitting unit;
A rotating polygon mirror capable of reflecting the light emitted from the irradiating means and scanning the image area and the non-image area on the photosensitive member;
Detection means for detecting the light reflected by the rotating polygon mirror;
A control unit configured to control light emission of the first light emitting unit and the second light emitting unit;
The control means is configured to control the image area and the non-image area by light emitted from the first light emitting unit during a start-up period in which the rotational speed is controlled such that the rotary polygon mirror rotates at a predetermined rotational speed. When the first light emitting unit is controlled to be the first light emission to be scanned, and light is detected at least twice by the detection unit while the first light emitting unit is performing the first light emission, The first light emitting unit is controlled to be a second light emission for scanning the non-image area by the light emitted from the first light emitting unit, and the light emitted from the second light emitting unit The second light emitting unit is controlled to be a third light emission for scanning a non-image area. A common light receiving unit that receives light from the first light emitting unit or receives light from the second light emitting unit;
The control unit adjusts the amount of light emitted from the first light emitting unit according to the amount of light received by the common light receiving unit during the period in which the first light emitting unit is performing the second light emission. 2. The light amount emitted from the second light emitting unit is adjusted according to the light amount received by the common light receiving unit in a period in which the second light emitting unit is performing the third light emission. Scanning device. First light receiving means for receiving light from the first light emitting unit;
And second light receiving means for receiving light from the second light emitting unit,
The control unit adjusts the amount of light emitted from the first light emitting unit in accordance with the amount of light received by the first light receiving unit during a period in which the first light emitting unit performs the second light emission. The light amount emitted from the second light emitting unit is adjusted according to the light amount received by the second light receiving unit during the period in which the second light emitting unit is performing the third light emission. The scanning device according to.   The said detection means outputs a horizontal synchronizing signal to the said control means according to detecting the light reflected by the said rotating polygon mirror, The said control means is described in any one of the Claims 1 thru | or 3 characterized by the above-mentioned. Scanning device.   The second light emission from the first light emitting unit and the second light emission from the first light emitting unit during a period from when the first horizontal synchronization signal is output by the detection unit to when the second horizontal synchronization signal is output next The scanning device according to claim 4, wherein the second light emission is performed by two light emitting units.   The first light emitting unit performs the second light emission at a timing at which light is detected by the detection unit, and the second light emitting unit performs the image area after the second light emission by the first light emitting unit. The scanning device according to any one of claims 1 to 5, wherein the third light emission is performed in a period until the scanning of. The irradiation unit further includes a third light emitting unit and a fourth light emitting unit,
When the light is detected at least twice by the detection unit while the first light emitting unit is performing the first light emission, the control unit causes the non-lighting by the light emitted from the third light emitting unit. The third light emitting unit is controlled to be the fourth light emission for scanning the image area, and the fifth light emission for scanning the non-image area by the light emitted from the fourth light emitting unit The scanning device according to claim 1, wherein the fourth light emitting unit is controlled. Light from the first light emitting unit is received, light from the second light emitting unit is received, light from the third light emitting unit is received, or light from the fourth light emitting unit is received Equipped with common light receiving means,
The control unit adjusts the amount of light emitted from the first light emitting unit according to the amount of light received by the common light receiving unit during the period in which the first light emitting unit is performing the second light emission. (2) adjusting the amount of light emitted from the second light emitting portion according to the amount of light received by the common light receiving unit during the period in which the second light emitting portion is performing the third light emission, and the third light emitting portion controls the fourth light emitting portion; Adjusting the amount of light emitted from the third light emitting unit according to the amount of light received by the common light receiving unit during the period of light emission, and the period during which the fourth light emitting unit is performing the fifth light emission 8. The scanning device according to claim 7, wherein the amount of light emitted from the fourth light emitting unit is adjusted in accordance with the amount of light received by the common light receiving unit. First light receiving means for receiving light from the first light emitting unit;
A second light receiving unit that receives light from the second light emitting unit;
Third light receiving means for receiving light from the third light emitting unit;
And fourth light receiving means for receiving the light from the fourth light emitting unit;
The control unit adjusts the amount of light emitted from the first light emitting unit in accordance with the amount of light received by the first light receiving unit during a period in which the first light emitting unit performs the second light emission. The amount of light emitted from the second light emitting unit is adjusted according to the amount of light received by the second light receiving unit during the period in which the second light emitting unit is performing the third light emission, and the third light emitting unit The amount of light emitted from the third light emitting unit is adjusted in accordance with the amount of light received by the third light receiving unit during the fourth light emission period, and the fourth light emitting unit performs the fifth light emission. 8. The scanning device according to claim 7, wherein the amount of light emitted from the fourth light emitting unit is adjusted in accordance with the amount of light received by the fourth light receiving unit during the period.   10. The detection method according to any one of claims 7 to 9, wherein the detection means outputs a horizontal synchronization signal to the control means in response to detection of the light reflected by the rotary polygon mirror. Scanning device.   The second light emission from the first light emitting unit and the second light emission from the first light emitting unit during a period from when the first horizontal synchronization signal is output by the detection unit to when the second horizontal synchronization signal is output next 11. The scanning device according to claim 10, wherein the third light emission by the second light emitting unit, the fourth light emission by the third light emitting unit, and the fifth light emission by the fourth light emitting unit are performed.   The second light emission is performed by the first light emitting unit during one cycle after the first horizontal synchronization signal is output by the detection unit and the second horizontal synchronization signal is output next; Furthermore, any one of the third light emission by the second light emitting unit, the fourth light emission by the third light emitting unit, and the fifth light emission by the fourth light emitting unit is performed. The scanning device according to 10.   The controller according to any one of claims 1 to 12, wherein the control unit causes the first light emitting unit to perform the first light emission after a predetermined time has elapsed since the rotation of the rotary polygon mirror is started. The scanning device according to claim 1.   13. The apparatus according to claim 1, wherein the control means controls the timing at which the first light emitting unit performs the first light emission according to an elapsed time from an instruction to stop the rotary polygon mirror. The scanning device according to any one of the preceding claims. A scanning device according to any one of the preceding claims,
Developing means for developing the electrostatic latent image formed by the scanning device;
A transfer unit for transferring an image developed by the developing unit to a recording material;
Fixing means for fixing the recording material to which the image has been transferred by the transfer means;
An image forming apparatus comprising: An irradiation unit having a first light emitting unit and a second light emitting unit;
A rotating polygon mirror capable of reflecting the light emitted from the irradiating means and scanning the image area and the non-image area on the photosensitive member;
Detection means for detecting the light reflected by the rotating polygon mirror;
An image forming apparatus including control means for controlling light emission of the first light emitting unit and the second light emitting unit;
The control means is configured to control the image area and the non-image area by light emitted from the first light emitting unit during a start-up period in which the rotational speed is controlled such that the rotary polygon mirror rotates at a predetermined rotational speed. When the first light emitting unit is controlled to be the first light emission to be scanned, and light is detected at least twice by the detection unit while the first light emitting unit is performing the first light emission, The first light emitting unit is controlled to be a second light emission for scanning the non-image area by the light emitted from the first light emitting unit, and the light emitted from the second light emitting unit An image forming apparatus, wherein the second light emitting unit is controlled to be a third light emission for scanning a non-image area.

Images