JP2019098524A - Image forming apparatus - Google Patents

Abstract

To control a very small amount of light emission in accordance with the speed of a rotary mirror in a startup period of the rotary mirror.SOLUTION: An image forming apparatus includes: control means for controlling light from a light source so as to be radiated to an image carrier in a first amount of light emission for forming a latent image in an image part, or a second amount of light emission being an amount of light emission smaller than the first amount of light emission to control a potential of a non-image part; and acquisition means for acquiring information related to a rotational speed of the rotary mirror and a rotational speed of the image carrier. The control means determines the second amount of light emission emitted from the light source in a startup period of the rotary mirror performed prior to image formation on the basis of a correspondence between the information related to the rotational speed of the rotary mirror and the rotational speed of the image carrier, and the second amount of light emission.SELECTED DRAWING: Figure 9

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic recording method.

Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic recording method, for example, the following electrophotographic process is performed.
First, the surface of the photosensitive drum is uniformly charged by the charging device. Thereafter, laser light is emitted by a laser exposure device to form an electrostatic latent image on the photosensitive drum. Then, a toner image is attached to the electrostatic latent image by the developing device, and the toner image is transferred to the transfer target by the transfer device. Further, toner remaining on the photosensitive drum is removed by the drum cleaning device.
In the electrophotographic image forming apparatus as described above, it is important to control the surface potential of the photosensitive drum in order to form an electrostatic latent image on the surface of the photosensitive drum. In order to control the surface potential of the photosensitive drum, the laser is so small as not to cause toner adhesion to the non-image portion (non-toner image forming portion) of the printable area of the photosensitive drum charged with a predetermined charging potential. There is known a method of controlling the surface potential of the photosensitive drum appropriately (hereinafter, light emission of non-image area) by emitting light (see Patent Document 1). Patent Document 1 proposes a method of changing the light emission amount in non-image area minute light emission for each printing speed.

JP, 2014-13373, A

  However, during the start-up period of the laser exposure apparatus (rotational mirror), the rotational speed of the rotational mirror is in a state of being accelerated to a predetermined speed. In such a state, there is a possibility that the surface potential of the photosensitive drum can not be properly controlled unless the amount of minute emission of the laser is appropriately controlled in accordance with the rotational speed of the rotating mirror.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to control a minute amount of light emission in accordance with the speed of a rotating mirror during a startup period of the rotating mirror.

In the present invention to achieve the above object,
An image carrier which is rotationally driven;
An irradiation unit having a rotary mirror that reflects light emitted from a light source toward the image carrier, and irradiating the light from the light source onto the image carrier to form a latent image;
A first light emission amount for forming the latent image in an image area, or a second light emission amount which is a light emission amount smaller than the first light emission amount and for controlling a potential of a non-image area Control means for causing the image carrier to emit light;
Acquisition means for acquiring information on the rotation speed of the rotating mirror and the rotation speed of the image carrier;
Have
The control means controls the rotational speed of the rotating mirror acquired by the acquiring means and the image carrying amount of the second light emission amount emitted from the light source during a rising period of the rotating mirror performed prior to image formation. It is characterized in that it is determined based on the correspondence relationship between the information on the rotational speed of the body and the second light emission amount.

  According to the present invention, it is possible to control the minute amount of light emission according to the speed of the rotating mirror during the startup period of the rotating mirror.

1 is a schematic cross-sectional view showing an image forming apparatus of Example 1 The figure which shows an example of the EV curve which shows the sensitivity characteristic of the photosensitive drum of Example 1 Diagram for explaining the relationship of the potential when the cumulative rotation time of the photosensitive drum changes The figure which shows the external appearance of the scanner unit of Example 1 Circuit diagram of a circuit for automatically adjusting the light emission level of the laser diode of Example 1 Diagram showing the functional blocks and hardware related to the engine controller Diagram for explaining the relationship of the potential when the rotational speed of the scanner unit changes A diagram showing an example of a pre-processing sequence of an image forming operation Flow chart for determining the second light emission level in the first embodiment FIG. 7 is a diagram showing an example of a pre-processing sequence of an image forming operation of Embodiment 2; Flow chart for determining the second light emission level in the second embodiment Diagram showing the functional blocks and hardware related to the engine controller Flow chart for determining the second light emission level in the third embodiment

DETAILED DESCRIPTION Exemplary embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, etc. of the components described in this embodiment should be changed as appropriate depending on the configuration of the apparatus to which the invention is applied and various conditions, and The scope of the present invention is not intended to be limited to the following embodiments.
Example 1
(Description of the image forming apparatus)
FIG. 1 is a schematic cross-sectional view showing an image forming apparatus 100 of the present embodiment. The configuration and operation of the image forming apparatus 100 of the present embodiment will be described below with reference to FIG.
The image forming apparatus 100 of this embodiment has first, second, third and fourth image forming units (image forming stations) a, b, c and d. The first, second, third and fourth image forming portions a, b, c and d are yellow (hereinafter Y), magenta (hereinafter M), cyan (hereinafter C) and black (hereinafter each). Bk) for forming an image of each color.

In the present embodiment, the configurations of the first to fourth image forming portions a to d are substantially the same except that the color of the toner (developer) to be used is different. Therefore, in the following, suffixes a, b, c and d given to reference numerals in the drawings are omitted to indicate that the elements are provided for any color unless distinction is particularly required. Explain it.
Each of the image forming units a to d is provided with a storage member (not shown) that stores the cumulative rotation time of the photosensitive drums 1 a to 1 d as information related to the life of the photosensitive drum. Each image forming station is replaceable with respect to the image forming apparatus main body. In addition, each image forming portion only needs to include at least the photosensitive drum 1, and it is not particularly limited as to which members are included in the image forming portion and made exchangeable.
In the following description, the unit of exposure (μJ / cm ² ), the unit of emission level (emission), (μJ / sec), the unit of speed (rotational speed, scanning speed) (cm / sec), time A unit (sec) may be abbreviated and described for convenience of explanation.

Hereinafter, the operation of the first image forming unit a will be described as an example.
The first image forming portion a has a photosensitive drum 1a as an image bearing member (photosensitive member). The photosensitive drum 1a is rotationally driven at a predetermined peripheral speed in the direction indicated by the arrow in FIG. 1 and is uniformly charged by the charging potential Vdcc applied to the charging roller 2a. Next, the image area on the surface of the photosensitive drum 1a is exposed with the exposure amount Ep for image formation by scanning of the laser beam 6a emitted from the scanner unit 31a as the irradiation unit based on the image data supplied from the outside. Thus, a latent image (electrostatic latent image) is formed. Further, the scanner unit 31a exposes the non-image area on the surface of the photosensitive drum 1a on which the latent image is not formed by the scanning of the laser beam 6a with the exposure amount Ebg for minute emission. At this time, the relationship between the exposure amount Ep and the exposure amount Ebg is controlled such that Ep> Ebg. Here, a light of an exposure amount Ep (first light emission amount) is irradiated from the scanner unit 31a to the image portion in order to cause the toner to adhere, and a latent image is formed. Further, the light of the exposure amount Ebg (second light emission amount) is irradiated from the scanner unit 31a to the non-image portion in order to prevent the toner from adhering.

  The Y toner adheres to the image portion (latent image) exposed with the exposure amount Ep and is visualized by the development potential Vdc applied to the developing device 4a. The non-image area exposed with the exposure amount Ebg has a potential at which the toner does not easily adhere (a potential at which the positive fog and the reverse fog are not easily generated), so the toner does not adhere. Here, the developing device 4a has a developing roller 3a, and the developing device 4a and the developing roller 3a constitute a developing means. In the present embodiment, the developing device 4a (developing roller 3a) is provided so as to be capable of coming into and coming out of contact with the photosensitive drum 1a. At the time of image formation, the photosensitive drum 1a and the developing device 4a are in contact with each other, the latent image formed on the photosensitive drum 1a is developed, and at the time of non-image formation, the photosensitive drum 1a and the developing device 4a are separated. Is configured to be possible.

Here, the charging and developing high voltage power source 52 will be described.
The charging / developing high-voltage power source 52 is connected to the charging rollers 2 and the developing rollers 3 corresponding to the respective colors. The charging / developing high-voltage power supply 52 supplies the charging voltage Vcdc output from the transformer 53 to each charging roller 2, and the developing voltage Vdc divided by the two resistance elements R3 and R4 is applied to each developing roller 3 (developing device It is supplied to 4). Since the charging / developing high-voltage power supply 52 simplifies the power supply system, the voltages supplied to the respective rollers can be collectively adjusted while maintaining a predetermined relationship. On the other hand, independent adjustment can not be performed for each color. The resistance elements R3 and R4 may be configured by any of fixed resistance, semi-fixed resistance, and variable resistance. Further, in the figure, the power supply voltage itself from the transformer 53 is directly input to each charging roller 2, and a divided voltage obtained by dividing the voltage output from the transformer 53 by a fixed voltage dividing resistor is directly applied to each developing roller 3. It is input. However, this is only an example, and it is not limited to this voltage input form as long as it is common to charging and common to development.

Also, in order to control the charging voltage Vcdc constant, the negative voltage obtained by stepping down the charging voltage Vcdc according to the following equation 1 is offset to the positive voltage by the reference voltage Vrgv to be the monitor voltage Vref, which becomes a constant value I am doing feedback control.
<Formula 1>
R2 / (R1 + R2)

Specifically, the control voltage Vc set in advance is input to the positive terminal of the operational amplifier 54, and the monitor voltage Vref is input to the negative terminal. Then, the output value of the operational amplifier 54 performs feedback control of the control and drive system of the transformer 53 so that the monitor voltage Vref becomes equal to the control voltage Vc. Thus, the charging voltage Vcdc output from the transformer 53 is controlled to be a target value.

The intermediate transfer belt 10 is stretched by stretching members 11, 12, 13 and is in contact with the photosensitive drum 1a. The intermediate transfer belt 10 is rotationally driven at the contact position in the same direction as the photosensitive drum 1 a and at the same peripheral speed. The Y toner image formed on the photosensitive drum 1a is transferred as follows. That is, the primary transfer voltage applied from the primary transfer high-voltage power supply 15a to the primary transfer roller 14a while the Y toner image passes through the contact portion (primary transfer portion) between the photosensitive drum 1a and the intermediate transfer belt 10. Is transferred onto the intermediate transfer belt 10 (primary transfer). The primary transfer residual toner remaining on the surface of the photosensitive drum 1a is cleaned and removed by the drum cleaning device 5a which is a cleaning means. Similarly, the M toner image of the second color, the C toner image of the third color, and the Bk toner image of the fourth color are formed, and sequentially superimposed on the intermediate transfer belt 10 and transferred to obtain a full color image.

  The secondary transfer high-voltage power supply 21 is a secondary transfer roller in the process of passing toner images of four colors on the intermediate transfer belt 10 at the contact portion (secondary transfer portion) between the intermediate transfer belt 10 and the secondary transfer roller 20. A secondary transfer voltage is applied to 20. Thus, the four color toner images on the intermediate transfer belt 10 are collectively transferred onto the surface of the recording material P fed from the feed roller 50. After that, the recording material P carrying the toner images of four colors is conveyed to the fixing device 30, where the toners of four colors are melted and mixed and fixed to the recording material P by being heated and pressed. By the above operation, a full color toner image is formed on the recording medium. Further, secondary transfer residual toner remaining on the surface of the intermediate transfer belt 10 is cleaned and removed by an intermediate transfer belt cleaning device 16.

(Description of sensitivity characteristics of photosensitive drum)
FIG. 2 is a view showing an example of an EV curve showing sensitivity characteristics of the photosensitive drum 1, the horizontal axis represents the exposure amount E (μJ / cm ² ) on the photosensitive drum surface, and the vertical axis represents the potential (V in the photosensitive drum surface). In the case of).
This EV curve shows the potential on the surface of the photosensitive drum 1 when the photosensitive drum 1 is charged with the charging voltage Vcdc and exposed with laser light so that the exposure amount on the surface of the photosensitive drum is E. There is. Also, this EV curve shows that a larger potential attenuation can be obtained by increasing the exposure amount E. Further, the high potential portion is an environment of a strong electric field, and since recombination of charge carriers (electron-hole pairs) generated by exposure is difficult to occur, large potential attenuation is exhibited even at a small exposure amount. On the other hand, in the low potential portion, generated carriers are likely to recombine, so that the phenomenon that the potential attenuation is small even for the exposure with a large exposure amount can be seen. Further, FIG. 2 shows an EV curve of an initial stage of starting to use the photosensitive drum 1 and an EV curve of a stage of continuing to use the photosensitive drum 1. The curve of the broken line is, for example, an EV curve in which the cumulative rotation time of the photosensitive drum 1 is about 100,000 seconds, and the EV curve is different in the cumulative rotation time (durability state) of the photosensitive drum 1. The sensitivity characteristic of the photosensitive drum 1 shown in FIG. 2 is an example, and the application of the photosensitive drum 1 having various EV curves is assumed in this embodiment.

(Relationship between exposure amount and cumulative rotation time of photosensitive drum)
3A to 3C are diagrams for explaining the relationship between the charging potential, the developing potential and the exposure potential when the cumulative rotation time of the photosensitive drum 1 changes.

FIG. 3A is a view showing the potential on the surface of the photosensitive drum 1 when exposed with the exposure amount Ep (μJ / cm ² ) and Ebg (μJ / cm ² ) in the photosensitive drum 1 at the initial stage of starting to use.
The photosensitive drum 1 is charged to a potential Vd by the charging potential Vcdc applied to the charging roller 2. The non-image portion of the surface of the photosensitive drum 1 has a potential of Vd_bg by being finely exposed with the exposure amount Ebg by scanning of the laser beam 6a of the scanner unit 31a. On the other hand, the image portion on the surface of the photosensitive drum 1 is exposed at the exposure amount Ep by the scanning of the laser beam 6a of the scanner unit 31a, so that the potential becomes Vd_p. In the image area where the potential has become Vd_p, toner adheres due to the potential difference (Vcont) between the development potential Vdc applied to the developing device 4 and the potential Vd_p. On the other hand, in the non-image area where the potential has become Vd_bg, toner is less likely to be attached due to the potential difference (Vback) between the development potential Vdc applied to the developing device 4 and the potential Vd_bg. In the present embodiment, the charging voltage Vcdc is approximately -1100 V,
The developing voltage Vdc is about -350V, the potential Vd is about -600 to about -700V, the potential Vd_bg
Is about -400 V, and the potential Vd_p is about -150 V.

FIG. 3B is a view showing the potential of the surface of the photosensitive drum 1 when exposed with the exposure amounts Ep and Ebg in the photosensitive drum 1 at a stage where the cumulative rotation time of the photosensitive drum 1 continues to be used up to about 100,000 seconds.
As compared with the potential of the photosensitive drum 1 at the initial stage of beginning to use described with reference to FIG. 3A, Vd1, Vd_bg1, and Vd_p1 become stronger than Vd, Vd_bg, and Vd_p. As a result, in the image area, the potential difference (Vcont1) between the development potential Vdc applied to the developing device 4 and the potential Vd_p1 becomes small, and the toner hardly adheres (thin). Further, in the non-image area, the potential difference (Vback1) between the development potential Vdc applied to the developing device 4 and the potential Vd_bg1 becomes large, and the toner tends to adhere (reversal fog is easily generated). For example, after continuing to use the first to fourth image forming portions a to d to a certain extent, only the first image forming portion a may be replaced with a new one by the user. In such a case, when exposure is performed with the same exposure amounts Ep and Ebg in the first to fourth image forming portions a to d, thin density and reverse fogging occur in the second to fourth image forming portions b to d. there is a possibility.

FIG. 3C is a view showing the potential of the photosensitive drum surface when exposed with the exposure amounts Ep1 and Ebg1 in the photosensitive drum at a stage where the cumulative rotation time of the photosensitive drum 1 continues to be used up to about 100,000 seconds.
By setting the exposure amounts Ep and Ebg to the exposure amounts Ep1 and Ebg1, it is possible to make the potential equal to the potential of the photosensitive drum 1 at the initial stage of using it.
As described above, by determining the exposure amounts Ep and Ebg according to the cumulative rotation time of the photosensitive drums 1 in each image forming portion, even after the cumulative rotation times of the respective photosensitive drums 1 have a difference, after exposure The potential of the photosensitive drum surface is made equal.
In each image forming unit, the exposure amount can be changed by changing the light emission level of the laser light 6 of the scanner unit 31. The light emission levels corresponding to the exposure amount Ep and the exposure amount Ebg are Wp (μJ / sec) and Wbg (μJ / sec).

(Description of the optical scanning device)
FIG. 4 is a view showing the appearance of the scanner units 31a to 31d.
The laser drive system circuit 130 operates according to the light emission level set by the engine controller 122 (see FIG. 5), whereby a drive current flows through the laser diode 107 which is a light emitting element (light source). Here, the engine controller 122 constitutes control means, acquisition means, and storage means. The engine controller 122 will be described later. The storage unit is not limited to one provided in the image forming apparatus, and may be provided in an external device other than the image forming apparatus.
The laser diode 107 emits the laser beam 6 at an intensity level corresponding to the drive current. The laser beam 6 emitted by the laser diode 107 is shaped into a beam by the collimator lens 134 and formed into a parallel beam, and then reflected by the polygon mirror (rotary mirror) 133 toward the photosensitive drum 1 to be a photosensitive drum. It is scanned in the horizontal direction of 1. Then, the scanned laser beam 6 is imaged by the fθ lens 132 on the surface of the photosensitive drum 1 rotating in the direction of the arrow around the rotation axis and is exposed in the form of dots. On the other hand, a reflection mirror 131 is provided corresponding to the scanning position on one end side of the photosensitive drum 1, and the laser beam projected on the scanning start position is directed to a BD (Beam Detect) synchronous detection sensor (hereinafter BD detection sensor) Is reflected. And based on the output of this BD detection sensor 121, the scanning start timing of a laser beam is determined.

(Description of laser drive system circuit (LD driver))
FIG. 5 is a circuit diagram of a laser drive system circuit 130 for automatically adjusting the light emission level of the laser diode 107. As shown in FIG.
The portion enclosed within the dotted line 130a frame corresponds to the laser drive system circuit 130 shown in FIG. The configuration within the dotted line 130b to 130d is the same as that within the dotted line 130a, and the configuration within the dotted line 130a to 130d corresponds to the laser drive system circuit 130 of each color in the color image forming apparatus. The configuration of the laser drive system circuit 130 of a specific color will be described below, but the laser drive system circuit 130 of other colors is also configured in the same manner, and redundant description will be omitted.
The laser drive system circuit 130 includes PWM smoothing circuits 140 and 150, comparator circuits 101 and 111, sample / hold circuits 102 and 112, and hold capacitors 103 and 113. The laser drive system circuit 130 further includes current amplification circuits 104 and 114, reference current sources (constant current circuits) 105 and 115, switching circuits 106 and 116, and a current-voltage conversion circuit 109. Further, although the details will be described later, portions 101 to 106 correspond to the first light intensity adjustment portion (first current adjustment portion), and portions 111 to 116 are the second light intensity adjustment portion (second current adjustment Section). And each of the light emission level for image formation (hereinafter, first light emission level) for light emission and light emission level for slight light emission (hereinafter, second light emission level) to be described later is a control means (first light intensity) for adjusting each light emission amount The adjustment unit and the second light intensity adjustment unit can control independently.

  The engine controller 122 outputs the PWM signal PWM1 to the PWM smoothing circuit 140. The PWM smoothing circuit 140 includes an inverter circuit 141, resistors 142 and 144, and a capacitor 143. The inverter circuit 141 inverts the PWM signal PWM1. The output of the inverter circuit 141 charges the capacitor 143 via the resistor 142 and is smoothed by the capacitor 143 to become a voltage signal. Then, the smoothed voltage signal is input to the terminal of the comparator circuit 101 as the reference voltage Vref11. Thus, the reference voltage Vref11 is determined by the pulse width of the PWM signal PWM1 and is controlled by the engine controller 122.

  Further, the engine controller 122 outputs the PWM signal PWM2 to the PWM smoothing circuit 150. The PWM smoothing circuit 150 includes an inverter circuit 151, resistors 152 and 154, and a capacitor 153. The inverter circuit 151 inverts the PWM signal PWM2. The output of the inverter circuit 151 charges the capacitor 153 via the resistor 152 and is smoothed by the capacitor 153 to be a voltage signal. Then, the smoothed voltage signal is input to the terminal of the comparator circuit 111 as the reference voltage Vref21. Thus, the reference voltage Vref21 is determined by the pulse width of the PWM signal PWM2 and is controlled by the engine controller 122. Note that the PWM signal may be directly output from the engine controller 122 without specifying it in both of the reference voltages Vref11 and Vref21.

In the OR circuit 124, the Ldrv signal of the engine controller 122 and the VIDEO signal from the video controller 123 are input to the input terminal, and the Data signal is output to the switching circuit 106 described later. The VIDEO signal is a signal based on image data sent from an external device such as a reader scanner connected externally and a host computer. Here, the VIDEO signal will be described in detail. The VIDEO signal is driven by image data of a multi-value signal (0 to 255) of 8 bits (= 256 gradations), for example, and is a signal for determining a laser emission time. Assuming that the pulse width when the image data is 0 is PWmin and the pulse width when the image data is 255 is PWmax, the pulse width PWn when the image data is n is a tone value between PWmin and PWmax. A proportional pulse width is generated, which is represented by Equation 2 below.
<Formula 2>
PWn = (n × (PWmax−PWmin) / 255) + PWmin

The case where the image data for controlling the laser diode 107 is 8 bits (= 256 gradations) is an example, and for example, 4 bits (= 16 gradations) or 2 bits (half gradation) after the halftone processing of the image data. It may be a multilevel signal of 4 gradations. The image data after halftone processing may be a binarized signal.

  The VIDEO signal output from the video controller 123 is input to the buffer 125 with an enable terminal (ENB), and the output of the buffer 125 is input to the OR circuit 124. At this time, the enable terminal is connected to a signal line to which the Venb signal from the engine controller 122 is output. The engine controller 122 also outputs an SH1 signal, an SH2 signal, a Base signal Ldrv signal, and a Venb signal, which will be described later. The Venb signal is used to mask the Data signal based on the VIDEO signal, and the timing (image mask period) of the image mask area can be created by setting the Venb signal to the disable state (off state).

  The first reference voltage Vref11 and the second reference voltage Vref21 are input to the positive terminals of the comparator circuits 101 and 111, respectively, and the outputs of the comparator circuits 101 and 111 are input to the sample / hold circuits 102 and 112, respectively. ing. The reference voltage Vref11 is set as a target voltage for causing the laser diode 107 to emit light at the first emission level. Further, the reference voltage Vref21 is set as a target voltage of the second light emission level. Hold capacitors 103 and 113 are connected to the sample / hold circuits 102 and 112, respectively. The outputs of the sample / hold circuits 102 and 112 are input to the positive terminals of the current amplification circuits 104 and 114, respectively.

  Reference current sources 105 and 115 are connected to the current amplification circuits 104 and 114, respectively, and the outputs thereof are input to the switching circuits 106 and 116. The third reference voltage Vref12 and the fourth reference voltage Vref22 are input to the negative terminals of the current amplification circuits 104 and 114, respectively. Here, the current Io1 (first drive current) is determined according to the difference between the output voltage of the sample / hold circuit 102 described above and the reference voltage Vref12. Further, Io2 (second drive current) is determined according to the difference between the output voltage of the sample / hold circuit 112 and the reference voltage Vref22. That is, Vref12 and Vref22 are voltage settings for determining the current.

The switching circuit 106 is turned on / off by the Data signal which is a pulse modulation data signal. The switching circuit 116 is turned on / off by the input signal Base. The output terminals of the switching circuits 106 and 116 are connected to the cathode of the laser diode 107 and supply drive currents Idrv and Ibg. The anode of the laser diode 107 is connected to the power supply Vcc. The cathode of a photodiode 108 (hereinafter referred to as PD 108) for monitoring the light quantity of the laser diode 107 is connected to the power supply Vcc, and the anode of the PD 108 is connected to a current voltage conversion circuit 109 to monitor current Im. Let flow. Thereby, the current voltage conversion circuit 109 converts the monitor current Im into the monitor voltage Vm. The monitor voltage Vm is non-feedback input to the negative terminals of the comparator circuits 101 and 111.
Although FIG. 5 separately shows the engine controller 122 and the video controller 123, the present invention is not limited to that form. For example, part or all of the engine controller 122 and the video controller 123 may be configured by the same controller. Also, with regard to the laser drive system circuit 130 surrounded by a dotted line frame in the drawing, for example, part or all of the laser drive system circuit 130 may be built in the engine controller 122.

  As described above, the engine controller 122 can control the drive current I (the light emission level W of the laser diode 107) flowing through the laser diode 107 by setting PWM1 and PWM2 to the laser drive system circuit 130. The light emission level W mentioned here is the amount of light emitted per unit time of the laser diode 107 for exposing the surface of the photosensitive drum 1 with the exposure amount E. Hereinafter, the light emission level when the drive current In flows through the laser diode 107 is set to Wn.

(Description of automatic adjustment of the light emission level W)
Next, automatic adjustment of the light emission level W of the laser diode 107 (drive current I in the laser drive system circuit 130) will be described. First, automatic adjustment of the light emission level Wdrv will be described. The engine controller 122 sets the sample / hold circuit 112 in the hold state (during the non-sampling period) and instructs the switching circuit 116 in the OFF operation state by the input signal Base in accordance with the instruction of the SH2 signal. Further, the engine controller 122 sets the sample / hold circuit 102 in the sampling state according to the instruction of the SH1 signal, and turns on the switching circuit 106 with the data signal. More specifically, at this time, the engine controller 122 controls the Ldrv signal, and sets the Data signal to be in a light emitting state of the laser diode 107.

In this state, when the laser diode 107 is in the full emission state (lighting maintenance state), the PD 108 monitors the emission intensity of the laser diode 107, and a monitor current Im1 proportional to the emission intensity flows. Then, by flowing the monitor current Im1 to the current voltage conversion circuit 109, the current voltage conversion circuit 109 converts the monitor current Im1 into the monitor voltage Vm1. Further, the current amplification circuit 104 controls the drive current Idrv based on Io1 flowing to the reference current source 105 so that the monitor voltage Vm1 matches the first reference voltage Vref11 which is the target value.
When an image is formed, the sample / hold circuit 102 is in a hold period (during a non-sampling period), and the switching circuit 106 is turned on / off according to the Data signal to apply pulse width modulation to the drive current Idrv.

  Next, automatic adjustment of the light emission level Wbg of the laser diode 107 (drive current Ibg in the laser drive system circuit 130) will be described. The engine controller 122 sets the sample / hold circuit 102 to the hold state (during the non-sampling period) according to the instruction of the SH1 signal, and turns the switching circuit 106 to the OFF operation state by the Data signal. With regard to this Data signal, the engine controller 122 disables the Venb signal connected to the enable terminal of the buffer 125 with the enable terminal, controls the Ldrv signal, and turns the Data signal off. Further, the engine controller 122 sets the sample / hold circuit 112 in the sampling state according to the instruction of the SH2 signal, turns on the switching circuit 116 by the input signal Base, and sets the laser diode 107 in the light emission state.

In this state, when the laser diode 107 is in the full emission state (lighting maintenance state), the PD 108 monitors the emission intensity of the laser diode 107, and a monitor current Im2 (Im1> Im2) proportional to the emission intensity flows. Then, by flowing the monitor current Im2 to the current voltage conversion circuit 109, the current voltage conversion circuit 109 converts the monitor current Im1 into the monitor voltage Vm2. Further, the current amplification circuit 114 controls the drive current Ibg based on Io2 flowing through the reference current source 115 so that the monitor voltage Vm2 matches the second reference voltage Vref21 which is the target value.
When an image is formed, the sample / hold circuit 112 is in the hold period (during the non-sampling period), and the entire light emission state is maintained.

(Description of the second light emission level)
The second light emission level (the second light emission amount) is such that a developer such as toner is not substantially charged (not developed) on the photosensitive drum 1 and the level of light emission intensity for improving the toner fogging state is set. I mean. The second light emission level is the light emission level Wbg when the drive current Ibg flows through the laser diode 107. That is, the second light emission level Wbg is a light emission amount of the laser diode 107 for exposing the non-image portion of the surface of the photosensitive drum 1 with the exposure amount Ebg to set the charging potential to Vd_bg. The second light emission level Wbg is the light emission intensity at which the laser diode 107 emits a laser. If the second light emission level Wbg is a light emission intensity which does not satisfy the laser light emission, the wavelength distribution of the spectrum is widely spread, and the wavelength distribution becomes wide with respect to the rated wavelength of the laser. As a result, the sensitivity of the photosensitive drum is disturbed and the surface potential becomes unstable. Therefore, the second light emission level Wbg needs to be the light emission intensity at which the laser diode 107 emits the laser light.

(Description of the first light emission level)
On the other hand, the first light emission level (the first light emission amount) means the level of the light emission intensity at which the charge adhesion of the developer to the photosensitive drum 1 is saturated. The first light emission level is the light emission level Wp when the drive current Ibg + Idrv flows through the laser diode 107. That is, the first light emission level Wp is obtained by exposing the image portion of the surface of the photosensitive drum 1 with the exposure amount Ep and setting the charging potential to Vd_p
Emission amount of the laser diode 107 for

  When the laser diode 107 is made to emit light at the first emission level Wp, the circuit of FIG. 5 is operated as follows. The engine controller 122 sets the sample / hold circuit 112 in the hold period, turns on the switching circuit 116, sets the sample / hold circuit 102 in the hold period, and turns on the switching circuit 106. Thus, the drive current Idrv + Ibg is supplied. Further, the drive current Ibg can be supplied (a second light emission level Wbg can be provided) in the OFF state of the switching circuit 106.

  The first light emission level Wp is a light emission intensity obtained by superimposing the PWM light emission level Wdrv by pulse width modulation on the second light emission level Wbg. A more specific description will be given below. The ON / OFF operation of the switching circuit 106 by the Data signal (VIDEO signal) when the SH2 and SH1 signals are set to the hold period and the Base signal is set to the ON state, and the engine controller 122 sets the Venb signal to the enabled state. Is done. This enables two levels of light emission between Ibg and Idrv + Ibg by the drive current, that is, Wbg to Wp (Wdrv + Wbg) by the light emission intensity.

  Thus, by operating the circuit of FIG. 5, the engine controller 122 can emit light as follows by the Data signal by the VIDEO signal sent from the video controller 123, and has two levels of light emission levels. Is possible. That is, the emission of the first emission level Wp and the emission of the second emission level Wbg in the laser emission region.

(Description of functional block diagram)
FIG. 6 is a diagram showing functional blocks and hardware 600 related to the engine controller 122. As shown in FIG.
The scanner motor control unit 610, the laser light amount switching unit 611, the laser light amount calculation unit 612, the BD detection unit 613, the scanner motor speed detection unit 614, and the drum motor control unit 615 respectively indicate functional blocks. Further, each of the drum motor cumulative rotation time measuring unit 616, the drum motor speed detecting unit 617, the charging / developing high voltage control unit 618, the system timer 619, and the development contact / separation control unit 620 also shows a functional block. The scanner motor 630, the laser drive system circuit 130, the laser diode 107, the BD detection sensor 121, the drum motor 632, the photosensitive drum 1, the charging roller 2, and the developing roller 3 each represent hardware. Further, each of the drum motor rotation period detection sensor 631, the charging / developing high voltage power source 52, the development contact / separation motor 633, and the development contact / separation cam mechanism 634 also indicates hardware. Each of these will be specifically described below.

The charging / developing high voltage control unit 618 controls the charging / developing high voltage power source 52 to apply a charging voltage to the charging roller 2 and a developing voltage to the developing roller 3.
The development contact and separation control unit 620 controls the development contact and separation motor 633 to drive the development contact and separation cam mechanism 634 to separate or contact the contact between the photosensitive drum 1a and the developing device 4a. Implement the development contact and separation operation to shift to the next.
The drum motor control unit 615 controls the drum motor 632 based on the information from the drum motor rotation period detection sensor 631. Specifically, first, the drum motor speed detection means 617 detects the rotation speed of the drum motor 632 based on the information acquired from the drum motor rotation period detection sensor 631. The drum motor control unit 615 controls the rotation speed of the drum motor 632 at the target speed (target rotation speed, rotation speed at the time of image formation) based on the rotation speed of the drum motor 632 detected by the drum motor speed detection unit 617. Control to be stable. The drum motor accumulated rotation time measuring unit 616 measures the accumulated rotation time of the drum motor 632 using the system timer 619 by the drum motor control unit 615. As the drum motor 632 rotates, the connected photosensitive drum 1, charging roller 2, and developing roller 3 are also rotated.

The scanner motor control unit 610 controls the scanner motor 630 that rotationally drives the polygon mirror 133 based on the information from the BD detection sensor 121. Specifically, the BD detection unit 613 detects the BD based on the information acquired from the BD detection sensor 121, and the scanner motor speed detection unit 614 detects the rotational speed of the scanner motor 630 based on the BD detected by the BD detection unit 613. To detect The scanner motor control means 610 stabilizes the rotational speed of the scanner motor 630 at the target speed (target rotational speed, rotational speed at the time of image formation) based on the rotational speed of the scanner motor 630 detected by the scanner motor speed detection means 614. To do control.
Next, the laser light amount calculation means 612 calculates the laser light amount from the cumulative rotation time of the drum motor 632, the rotation speed of the scanner motor 630, and the rotation speed of the drum motor 632. Here, the cumulative rotation time of the drum motor 632 is measured by the drum motor cumulative rotation time measuring means 616. The rotational speed of the scanner motor 630 is detected by a scanner motor speed detection unit 614. Further, the rotational speed of the drum motor 632 is detected by the drum motor speed detection means 617. Then, the laser light amount switching unit 611 sets the laser light amount calculated by the laser light amount calculation unit 612 in the laser drive system circuit 130, and the laser diode 107 emits light. Here, the rotation speed of the scanner motor 630 corresponds to the rotation speed of the polygon mirror 133, and the rotation speed of the drum motor 632 corresponds to the rotation speed of the photosensitive drum 1.

(Relationship between exposure dose and scanning speed of scanner unit)
7A to 7C are diagrams for explaining the relationship between the charging potential, the developing potential and the exposure potential when the rotational speed of the scanner unit 31 changes.
In FIG. 7A, the scanner unit 31 during start-up scans at the speed Vx in the horizontal direction of the photosensitive drum 1 with respect to the surface of a new photosensitive drum 1 rotating at the speed Vy and emits light at the second light emission level Wbg. It is a figure which shows the electric potential of the photosensitive drum 1 surface in the case. In the following description, the velocity Vx may be referred to as a scanning velocity of the scanner unit 31. Here, the speed Vx corresponds to information on the rotational speed of the polygon mirror 133 (scanner motor 630). Further, the speed Vy corresponds to information on the rotational speed of the photosensitive drum 1 (drum motor 632).
FIG. 7B is a diagram showing the potential on the surface of the photosensitive drum 1 when the scanning speed of the scanner unit 31 is Vx / 2. From FIGS. 7A and 7B, when the scanning speed of the scanner unit 31 is halved, the exposure amount Ebg per unit area of the surface of the photosensitive drum 1 is doubled, and the values of Vback and Vback2 are different (the fog is different) It becomes clear that it becomes easy to occur.
FIG. 7C is a diagram showing the potential on the surface of the photosensitive drum 1 when the scanning speed of the scanner unit 31 is Vx / 2 and the second light emission level is Wbg / 2. As described above, by changing the second light emission level according to the scanning speed of the scanner unit 31, it is possible to set the potential at which fogging is unlikely to occur.

The correspondence between the exposure amount Ebg, the scanning speed of the scanner unit 31, and the second light emission level Wbg / 2 described with reference to FIGS. 7A to 7C will be described using equations.
Equation 3 is a unit area of the surface of the photosensitive drum 1 when the surface of the photosensitive drum 1 rotating at the velocity Vy is scanned at the scanning velocity Vx of the scanner unit 31 and exposed for the time T at the second light emission level Wbg. It is a formula for calculating the per-exposure amount Ebg.
<Formula 3>
Ebg = (T × Wbg) / ((T × Vx) × (T × Vy))

The surface of the photosensitive drum 1 per unit area when the surface of the photosensitive drum 1 rotating at the velocity Vy is scanned at the scanning velocity Vx / 2 of the scanner unit 31 and exposed for the time T at the second light emission level Wbg. The exposure amount Ebg2 can be calculated as shown in Formula 4. From equation 4, it can be seen that the exposure dose is twice that of Ebg.
<Formula 4>
Ebg2 = (T × Wbg) / ((T × Vx / 2) × (T × Vy))
= 2 x (T x Wbg) / ((T x Vx) x (T x Vy))
= 2 x Ebg

The unit area of the surface of the photosensitive drum 1 when the surface of the photosensitive drum 1 rotating at the velocity Vy is scanned at the scanning velocity Vx / 2 of the scanner unit 31 and exposed for the time T at the second light emission level Wbg / 2. The per-exposure dose Ebg3 can be calculated as shown in equation 5. From equation 5, it can be seen that the exposure dose is equal to Ebg.
<Formula 5>
Ebg3 = (T × Wbg / 2) / ((T × Vx / 2) × (T × Vy))
= (T x Wbg) / ((T x Vx) x (T x Vy))
= Ebg

That is, when the scanner motor 630 is at the target speed and the scanning speed of the scanner unit 31 is stable, the light emission can be made Ebg by emitting light at the second light emission level Wbg. However, in a state where the scanning speed of the scanner unit 31 is not stable as when the scanner motor 630 is rising, it is difficult to maintain a constant exposure amount when light is emitted at the second light emission level Wbg. Therefore, when the scanning speed of the scanner unit 31 is not stable, it is necessary to emit light at the second light emission level corresponding to the scanning speed of the scanner unit 31.

(Pre-processing sequence of image forming operation)
Hereinafter, an example of processing (hereinafter, pre-processing sequence of the image forming operation) performed prior to the image forming operation will be described with reference to FIGS. 8A and 8B.
In the pre-processing sequence of the image forming operation, the engine controller 122 acquires information relating to the velocity Vy of the surface of the photosensitive drum 1. The engine controller 122 detects the rotation speed of the drum motor 632 by the drum motor speed detection unit 617 as information related to the speed Vy. In addition, the engine controller 122 acquires information related to the scanning speed Vx of the scanner unit 31. The engine controller 122 detects the rotational speed of the scanner motor 630 by the scanner motor speed detection unit 614 as information related to the scanning speed Vx.
The engine controller 122 uses such information to perform a pre-processing sequence of the image forming operation. This will be described in more detail below.

8A and 8B are diagrams showing an example of the pre-processing sequence of the image forming operation, and FIG. 8A shows a comparative example and FIG. 8B shows the present embodiment. In addition, for convenience of explanation, also in a comparative example, it demonstrates using the structure similar to a present Example.
First, a pre-processing sequence of the image forming operation in the comparative example shown in FIG. 8A will be described. The engine controller 122 starts and starts up the drum motor 632 and the scanner motor 630 prior to the start of the image forming operation. When the rotational speed of the scanner motor 630 reaches a predetermined range with respect to the target speed (800), laser light emission is started at the second light emission level Wbg, and the contact relationship between the photosensitive drum 1 and the developing device 4 The development contact operation to shift to the contact state is started. When the developing contact operation is completed and the photosensitive drum 1 and the developing device 4 come into contact (801), image formation is started.

  In the comparative example, since it is difficult to keep the exposure amount on the surface of the photosensitive drum constant during startup of the scanner motor 630, the rotational speed of the scanner motor 630 falls within a certain range with respect to the target speed. You need to wait until you reach. Therefore, the start timing of the image formation is also delayed, and there is a concern that the first print time may become long.

On the other hand, in the present embodiment, during startup of the scanner motor 630, laser light is emitted at the second light emission level Wbg adjusted according to the rotational speed of the scanner motor 630 to make the exposure amount Ebg of the photosensitive drum surface constant. It is characterized by keeping. The method will be described below.
The exposure amount per unit area of the surface of the photosensitive drum 1 when the scanner unit 31 is rotated at the scanning speed Vx_c and exposed for the time T at the second light emission level Wbg_c with respect to the surface of the photosensitive drum 1 rotating at the speed Vy. Ebg_c can be calculated as Expression 6.
<Formula 6>
Ebg_c = (T × Wbg_c) / ((T × Vx_c) × (T × Vy))

The second light emission level Wbg for keeping the exposure amount Ebg on the surface of the photosensitive drum constant even during startup of the scanner motor 630 can be calculated as shown in Expression 7. Therefore, it is understood from the relationship defined by Equation 7 that the exposure amount can be made equal by determining the second light emission level in accordance with the speed ratio of the target speed of the scanner motor 630 and the rotational speed during start-up. . At this time, the photosensitive drum 1 is rotating at the speed Vy. In this state, the drum motor 632 reaches the target speed and the rotational speed of the drum motor 632 is stable.
The engine controller 122 stores the correspondence between the rotation speed of the drum motor 632 and the scanning speed of the scanner unit 31 obtained from Expression 7 or Expression 7 and the second light emission level. Thus, the engine controller 122 can determine the optimal second light emission level according to the scanning speed of the scanner unit 31 in the startup period of the scanner motor 630 in the state where the rotational speed of the drum motor 632 is stable. . In Equation 7, the second light emission level is determined according to the speed ratio between the target speed of the scanner motor 630 and the rotational speed, but the second light emission level is also considered in consideration of the cumulative rotation time of the photosensitive drum 1 Should be determined.
<Formula 7>
Ebg_c = Ebg
(T × Wbg_c) / ((T × Vx_c) × (T × Vy)) = (T × Wbg) / ((T × Vx) × (T × Vy))
Wbg_c = Wbg × Vx_c / Vx

An example of the pre-processing sequence of the image forming operation in this embodiment will be described below with reference to FIG. 8B.
The engine controller 122 activates the drum motor 632 and the scanner motor 630 prior to the start of the image forming operation. The light is not emitted from the scanner unit 31a until the rotational speed of the drum motor 632 is stabilized. When the drum motor 632 reaches the target speed and the rotational speed of the drum motor 632 is stabilized (810), the second light emission level is determined from the rotational speed of the scanner motor 630 based on the relationship of Equation 7. Then, the laser light emission to the photosensitive drum surface is started at the determined second light emission level, and the development contact operation is started. If the relationship between the start timing of the laser light emission and the start timing of the development contact operation is such that the surface of the photosensitive drum 1 is irradiated by the laser light so that no fog toner is generated when the development contact operation is started. Good.
The engine controller 122 switches to the second light emission level according to the rotational speed of the scanner motor 630 based on the relationship of Equation 7 in the startup period (section 813) of the scanner motor 630. During startup of the scanner motor 630 of the present embodiment, as shown in FIG. 8B, the higher the rotational speed of the scanner motor 630, the larger the second light emission level. When the rotational speed of the scanner motor 630 reaches a predetermined range with respect to the target speed (811), the second light emission level becomes Wbg. The engine controller 122 starts image formation when the developing contact operation is completed and the photosensitive drum 1 and the developing device 4 come into contact with each other (812).

As a result, even during the startup of the scanner motor 630, the potential on the surface of the photosensitive drum can be in a state where toner fog does not occur.
Further, in the present embodiment shown in FIG. 8B, the start timing of the developing contact operation can be set earlier by the amount shown in 814, as compared with the comparative example shown in FIG. 8A. As a result, the timing to start image formation can be set more quickly, and the first print time can also be shortened.

(Description of the flowchart)
FIG. 9 is a flowchart in the case of determining the second light emission level in accordance with the rotational speed of the scanner motor 630 in the present embodiment.
Prior to the image forming operation, the engine controller 122 activates the scanner motor 630 and the drum motor 632 by the scanner motor control unit 610 and the drum motor control unit 615 (S901, S902). The engine controller 122 detects the rotational speed of the drum motor 632 by the drum motor speed detection means 617 (S903), and waits for the rotational speed of the drum motor 632 to be stabilized (the drum motor 632 reaches the target speed) (S904) . At this time, the engine controller 122 sets the second light emission level Wbg_c to 0 and does not perform laser light emission until the rotational speed of the drum motor 632 is stabilized.
When the rotational speed of the drum motor 632 is stabilized (Yes in S904), the rotational speed of the scanner motor 630 is detected by the scanner motor speed detection unit 614 (S905). Then, the second light emission level Wbg_c is calculated and determined based on the detected rotational speed of the scanner motor 630 and the target speed of the scanner motor 630 (S9).
06). The engine controller 122 starts laser light emission to the surface of the photosensitive drum at the determined second light emission level Wbg_c (S 907), and starts a development contact operation (S 908). Further, the engine controller 122 detects the rotational speed of the scanner motor 630 by the scanner motor speed detection unit 614 (S909). Then, according to the detected rotational speed of the scanner motor 630, the second light emission level Wbg_c is calculated and determined by the laser light amount calculation means 612 (S910). Then, the engine controller 122 switches to the determined second light emission level Wbg_c and continues laser light emission (S911). Engine controller 12
2 repeats the series of control in S909 to S911 until it is determined that the developing contact operation is completed (S912), and when the scanner motor 630 is started and the developing contact operation is completed (Yes in S912), image formation It starts (S913).

As described above, in the present embodiment, when the rotational speed of the drum motor 632 is stabilized, the second light emission level is determined according to the speed ratio between the target speed of the scanner motor 630 and the rotational speed. As a result, even during the startup of the scanner motor 630, the potential on the surface of the photosensitive drum can be in a state where toner fog does not occur.
Further, in the configuration in which the photosensitive drum 1 and the developing device 4 can be brought into contact with or separated from each other as in this embodiment, the start timing of the development contact operation can be set earlier. The first print time can also be shortened.

  Here, in the present embodiment, although the embodiment has been described in which the photosensitive drum 1 and the developing device 4 have the contact / separation mechanism capable of coming into and out of contact, the present invention is not limited thereto. The present invention can be suitably applied even in a mode in which the developing device 1 and the developing device 4 are always in contact with each other. In the conventional mode in which the photosensitive drum 1 and the developing device 4 are always in contact with each other, it is necessary to set the second light emission level to Wbg from the start of motor startup and until the drum motor and scanner motor start up. There is a concern that fog toner may be generated. On the other hand, when the present invention is applied to a configuration in which the photosensitive drum 1 and the developing device 4 are always in contact with each other, the second light emission level needs to be Wbg at the start of motor startup as in the conventional embodiment. is there. However, after the drum motor rises, as shown in FIG. 8B, light can be emitted at the second light emission level corresponding to the rotational speed of the scanner motor. Therefore, even in the embodiment in which the present invention is applied to the configuration in which the photosensitive drum 1 and the developing device 4 are always in the abutting state, compared with the conventional embodiment in which the second light emission level is changed to Wbg from the start of motor startup. It is possible to suppress the generation of toner.

Example 2
The second embodiment will be described below.
In the first embodiment, the case where the rotational speed of the scanner motor 630 during the startup of the scanner motor 630 is considered is described. However, in the first embodiment, since the rotational speed of the drum motor 632 during startup of the drum motor 632 is not taken into consideration, it may be necessary to wait until the rotational speed of the drum motor 632 stabilizes at the target speed.
Therefore, in the present embodiment, an operation of determining the second light emission level Wbg in accordance with the rotational speed of the scanner motor 630 during startup of the scanner motor 630 and the rotational speed of the drum motor 632 during startup of the drum motor 632 will be described. . In the present embodiment, configurations and processes different from the first embodiment will be described, and descriptions of configurations and processes similar to the first embodiment will be omitted.

(Description of how to determine the second emission level)
The exposure amount per unit area of the surface of the photosensitive drum 1 when the photosensitive drum 1 rotating at the speed Vy_c rotates at the scanning speed Vx_c of the scanner unit 31 and is exposed for the time T at the second light emission level Wbg_c. Ebg_c can be calculated as Equation 8.
<Equation 8>
Ebg_c = (T × Wbg_c) / ((T × Vx_c) × (T × Vy_c))

Even during startup of the scanner motor 630 and the drum motor 632, the second light emission level Wbg for keeping the exposure amount Ebg on the surface of the photosensitive drum constant can be calculated as Expression 9. Therefore, the second light emission level is determined according to the speed ratio of the target speed of the scanner motor 630 to the rotational speed during start-up and the speed ratio of the target speed of the drum motor 632 to the rotational speed during start-up from Eq. It can be seen that the exposure amount can be made equal. Here, the engine controller 122 stores the correspondence between the rotational speed of the drum motor 632 and the scanning speed of the scanner unit 31 obtained from Expression 9 or Expression 9 and the second light emission level.
<Expression 9>
Ebg_c = Ebg
(T × Wbg_c) / ((T × Vx_c) × (T × Vy_c)) = (T × Wbg) / ((T
X Vx) x (T x Vy))
Wbg_c = Wbg × (Vx_c / Vx) × (Vy_c / Vy)

(Description of the timing chart)
FIG. 10 is a diagram showing an example of the pre-processing sequence of the image forming operation according to the present embodiment.
A solid line 1000 represents the rotational speed of the scanner motor 630, and a broken line 1001 represents the rotational speed of the drum motor 632. Prior to the start of the image forming operation, the engine controller 122 activates the drum motor 632 and the scanner motor 630 and determines the second light emission level from the rotational speed of the scanner motor 630 and the rotational speed of the drum motor 632. Then, laser light emission is started at the determined second light emission level and the development contact operation is started (1002). The engine controller 122 switches to the second light emission level according to the rotational speed of the scanner motor 630 and the drum motor 632 based on the equation 9 in the rising period (section 1005) of the scanner motor 630 and the drum motor 632. While the rotational speed of the drum motor 632 reaches the target speed and is in a stable state and the scanner motor 630 is in a rising period (section 1006), the second light emission level according to the rotational speed of the scanner motor 630 (Example Switch to the second light emission level described in 1.). When the rotational speed of the scanner motor 630 reaches a predetermined range with respect to the target speed (1003), the second light emission level becomes Wbg. The engine controller 122 starts image formation when the developing contact operation is completed and the photosensitive drum 1 and the developing device 4 come into contact with each other (1004).

  As described above, in the present embodiment, the second light emission level is determined according to the rotational speed of the scanner motor 630 and the rotational speed of the drum motor 632. As a result, it is not necessary to wait until the drum motor 632 reaches the target speed, and compared with the method described in the first embodiment, the start timing of the development contact operation can be made earlier by the amount shown in FIG. As a result, the timing to start the image formation can be made earlier, and the first print time can also be shortened.

(Description of the flowchart)
FIG. 11 is a flowchart in the case of determining the second light emission level in accordance with the rotational speed of the scanner motor 630 and the rotational speed of the drum motor 632 in the present embodiment.
Prior to the image forming operation, the engine controller 122 activates the scanner motor 630 and the drum motor 632 by the scanner motor control unit 610 and the drum motor control unit 615 (S1101 and S1102). The engine controller 122 detects the rotational speed of the drum motor 632 by the drum motor speed detection unit 617 (S1103), and detects the rotational speed of the scanner motor 630 by the scanner motor speed detection unit 614 (S1104). Next, the second light emission level Wbg_c is calculated and determined based on the detected rotational speed of the drum motor 632 and the rotational speed of the scanner motor 630 (S1105). The engine controller 122 starts laser light emission at the determined second light emission level Wbg_c (S1106), and starts the development contact operation (S1107).
Further, the engine controller 122 detects the rotational speed of the drum motor 632 by the drum motor speed detection means 617 (S1108), and the scanner motor speed detection means 61
The rotational speed of the scanner motor 630 is detected at 4 (S1109).
Next, the second light emission level Wbg_c is determined according to the rotational speed of the drum motor and the rotational speed of the scanner motor 630 detected by the drum motor speed detection unit 617 (S1110), and the determined second light emission level Wbg_c is switched (S1111). ). Engine controller 1
22 repeats the control of S1108 to S1111 until the development contact operation is completed (S1112), and when the development contact operation is completed (Yes in S1112), image formation is started (S1113).

As described above, in the present embodiment, the second light emission level is determined according to the speed ratio of the target speed to the rotational speed of the scanner motor 630 and the speed ratio of the target speed to the rotational speed of the drum motor 632. As a result, even while the scanner motor 630 and the drum motor 632 are activated, the potential on the surface of the photosensitive drum can be in a state where toner fog does not occur.
Furthermore, in the configuration in which the photosensitive drum 1 and the developing device 4 can be brought into contact and separated as in this embodiment, the developing contact operation can be started from the start of startup of the motor. It can be set quickly and the first print time can be further shortened.
Also in the present embodiment, although the embodiment has been described in which the photosensitive drum 1 and the developing device 4 have a contact / separation mechanism capable of coming into and out of contact, the present invention is not limited to this. The present invention can be suitably applied even in a mode in which the developing device 1 and the developing device 4 are always in contact with each other. Also in this embodiment, it is possible to realize laser light emission at the optimum second light emission level from the start of startup of the motor. Therefore, when the photosensitive drum 1 and the developing device 4 are always in contact with each other, the embodiment of the present embodiment is more effective than the embodiment of the embodiment 1 in that the potential of the photosensitive drum surface is increased during startup of the motor. It is possible to prevent toner fogging.

Here, when the scanner motor 630 and the drum motor 632 are activated prior to the image forming operation, the startup periods of the scanner motor 630 and the drum motor 632 differ depending on the state of the image forming apparatus, the specifications of the image forming apparatus, etc. .
In the present embodiment, the drum motor 632 starts first and then the scanner motor 630 starts. However, the present invention is not limited thereto. The drum motor 632 may start up after the scanner motor 630 starts up. Even in such a case, it is possible to determine the second light emission level according to the rotational speed of the scanner motor 630 and the rotational speed of the drum motor 632 by following the flowchart shown in FIG. In such a case, the second light emission level may be determined according to the rotational speed of the drum motor 632 during the period until the drum motor 632 starts up after the scanner motor 630 rises.
In addition, the image forming operation may be performed immediately after stopping the previous image forming operation. In such a case, when the scanner motor 630 and the drum motor 632 are activated prior to the image forming operation, one of the scanner motor 630 and the drum motor 632 may immediately start up. As described above, when the rotational speed of one of the motors is at the target speed immediately after the two motors are started, the second light emission level described in the first embodiment corresponds to the rotational speed of the other motor. The second light emission level may be determined.

[Example 3]
The third embodiment will be described below.
In the first and second embodiments, the method of determining the second light emission level in accordance with the rotational speed of the scanner motor 630 has been described. However, in these embodiments, since the time constant of the PWM smoothing circuit 150 is not taken into consideration, when the time constant is large, the amount of light emission of the laser diode 107 is actually switched after switching the second light emission level. Time difference becomes longer. In that case, when the light emission amount of the laser diode 107 is switched, the rotational speed of the scanner motor 630 during start-up also changes, so the exposure amount on the surface of the photosensitive drum 1 decreases and toner fog easily occurs. there is a possibility.
Therefore, the present embodiment is characterized in that prediction means for predicting the speed of the scanner motor 630 is provided, and the light emission level Wbg is determined according to the speed prediction result of the scanner motor 630 and the rotational speed of the drum motor 632. Here, the prediction means assumes that the light emitted at the second light emission level determined using the rotational speed of the scanner motor 630 detected by the scanner motor speed detection means 614 is irradiated on the surface of the photosensitive drum 1. , The rotational speed of the scanner motor 630 is predicted. Then, using the rotational speed of the scanner motor 630 predicted by the prediction means instead of the rotational speed of the scanner motor 630 detected by the scanner motor speed detection means 614, the second light emission amount is calculated in the same manner as the above embodiment. decide. In the present embodiment, configurations and processes that are different from the first and second embodiments will be described, and descriptions of configurations and processes similar to the first and second embodiments will be omitted.

(Description of functional block diagram)
FIG. 12 is a diagram showing functional blocks related to the engine controller 122 and hardware 600.
The engine controller 122 does not have the laser light amount calculating means 612 in the first and second embodiments, but has a laser light amount calculating means 1200 and also has a scanner motor speed predicting means 1201 anew. The scanner motor speed prediction unit 1201 calculates the predicted speed of the scanner motor 630 from the rotational speed of the scanner motor 630 detected by the scanner motor speed detection unit 614. The laser light amount calculating means 1200 calculates the laser light amount from the predicted speed of the scanner motor 630 calculated by the scanner motor speed predicting means 1201, the cumulative rotation time of the drum motor 632 and the rotational speed of the drum motor 632. Here, the cumulative rotation time of the drum motor 632 is measured by the drum motor cumulative rotation time measuring means 616. Further, the rotational speed of the drum motor 632 is detected by the drum motor speed detection means 617.

(Description of the flowchart)
FIG. 13 is a flow chart in the case of determining the second light emission level in accordance with the predicted speed of the scanner motor 630 and the rotational speed of the drum motor 632 in the present embodiment.
The engine controller 122 activates the scanner motor 630 and the drum motor 632 by the scanner motor control means 610 and the drum motor control means 615 prior to the image forming operation (S1301, S1302). The engine controller 122 detects the rotational speed of the drum motor 632 by the drum motor speed detection unit 617 (S1303), and calculates the predicted speed of the scanner motor 630 by the scanner motor speed prediction unit 1201 (S1304). Next, the laser light quantity calculating means 1200 calculates the second light emission level according to the rotational speed of the drum motor 632 detected by the drum motor speed detecting means 617 and the predicted speed of the scanner motor 630 calculated by the scanner motor speed predicting means 1201 Is determined (S1305). At this time, as in the first embodiment, the second light emission level may be determined in consideration of the cumulative rotation time of the photosensitive drum 1. The engine controller 122 starts laser light emission at the determined second light emission level Wbg_c (S1306), and starts the development contact operation (S1307).
).

Further, the engine controller 122 detects the rotational speed of the drum motor 632 by the drum motor speed detection unit 617 (S1308), and calculates the predicted speed of the scanner motor 630 by the scanner motor speed prediction unit 1201 (S1309). Next, the laser light quantity calculating means 1200 calculates the second light emission level according to the rotational speed of the drum motor 632 detected by the drum motor speed detecting means 617 and the predicted speed of the scanner motor 630 calculated by the scanner motor speed predicting means 1201. It is calculated and decided (S1310). The engine controller 122 switches to the determined second light emission level Wbg_c (S1311). The engine controller 122 repeats the control of S1308 to S1311 until the developing contact operation is completed (S1312), and when the developing contact operation is completed (Yes in S1312), starts image formation (S1313).

As described above, in the present embodiment, the second light emission level is determined according to not the detection result of the rotational speed of the scanner motor 630 but the speed prediction result. As a result, even when the time constant of the PWM smoothing circuit 150 is large, the potential on the surface of the photosensitive drum can be in a state in which toner fog does not occur.
Here, in the present embodiment, although the operation using only the speed prediction result of the scanner motor 630 has been described, the present invention is not limited to this, and a prediction result in which the rotational speed of the drum motor 632 is predicted may be used. That is, it is sufficient to use the predicted result obtained by predicting the rotational speed of the scanner motor 630 and / or the rotational speed of the drum motor 632 when determining the second light amount.

  Reference Signs List 1 photosensitive drum 31 scanner unit 107 laser diode 122 engine controller 133 polygon mirror

Claims (12)

An image carrier which is rotationally driven;
An irradiation unit having a rotary mirror that reflects light emitted from a light source toward the image carrier, and irradiating the light from the light source onto the image carrier to form a latent image;
A first light emission amount for forming the latent image in an image area, or a second light emission amount which is a light emission amount smaller than the first light emission amount and for controlling a potential of a non-image area Control means for causing the image carrier to emit light;
Acquisition means for acquiring information on the rotation speed of the rotating mirror and the rotation speed of the image carrier;
Have
The control means controls the rotational speed of the rotating mirror acquired by the acquiring means and the image carrying amount of the second light emission amount emitted from the light source during a rising period of the rotating mirror performed prior to image formation. An image forming apparatus characterized by determining based on the correspondence between information on the rotational speed of the body and the second light emission amount. The control means
In the period until the rotational speed of the image carrier reaches the target rotational speed, based on the correspondence between the information on the rotational speed of the rotary mirror and the rotational speed of the image carrier and the second light emission amount, Determine the second light emission amount;
During a period in which the rotational speed of the image carrier reaches the target rotational speed, the relationship between the rotational speed of the rotating mirror and the target rotational speed of the image carrier and the second light emission amount is used. The image forming apparatus according to claim 1, wherein the second light emission amount is determined. The control means
In the period until the rotational speed of the image carrier reaches a target rotational speed, the second light emission amount is set to 0,
During a period in which the rotational speed of the image carrier reaches the target rotational speed, the relationship between the rotational speed of the rotating mirror and the target rotational speed of the image carrier and the second light emission amount is used. The image forming apparatus according to claim 1, wherein the second light emission amount is determined. The image forming apparatus according to any one of claims 1 to 3, wherein the second light emission amount is larger as the rotation speed of the rotating mirror or the rotation speed of the image carrier is higher. Information on the rotational speed of the rotating mirror and the rotational speed of the image carrier so that the exposure amount of the surface of the image carrier when irradiated with the light emitted with the second light emission amount becomes constant; The image forming apparatus according to any one of claims 1 to 4, wherein a correspondence relationship with the second light emission amount is defined. The correspondence relationship is defined using a ratio of a rotational speed of the rotating mirror to a target rotational speed of the rotating mirror and a ratio of a rotational speed of the image carrier to a target rotational speed of the image carrier. The image forming apparatus according to claim 5, The image carrier is provided so as to be capable of coming into and coming out of contact with the image carrier, and has a developing unit for developing a latent image formed on the surface of the image carrier in a state of being in contact with the image carrier.
The control means shifts the contact relationship between the image carrier and the developing means from the separated state to the abutting state when light emission from the light source is started with the second light emission amount in the rising period. The image forming apparatus according to any one of claims 1 to 6, wherein the operation is started. After light emission from the light source is started with the second light emission amount in the start-up period, the control means acquires information on the rotational speed of the rotating mirror and the rotational speed of the image carrier by the acquisition means The second light emission amount is determined from the obtained information, switched to the determined second light emission amount to continue light emission from the light source, and it is determined whether the contact relationship is in the contact state The image forming apparatus according to claim 7, wherein the series of operations are repeated until it is determined that the contact relationship is in the contact state. 9. The image formation according to claim 8, wherein the control means starts image formation when it is determined that the rotating mirror and the image carrier stand up and the contact relationship is in the contact state. apparatus. When the image carrier is irradiated with light emitted at the second light emission amount determined using the information on the rotation speed of the rotating mirror and the rotation speed of the image carrier acquired by the acquisition unit And prediction means for predicting the rotational speed of the rotating mirror and the rotational speed of the image carrier,
The control unit determines the second light emission amount using the rotation speed of the rotating mirror and the rotation speed of the image carrier predicted by the prediction unit instead of the information acquired by the acquisition unit. The image forming apparatus according to any one of claims 1 to 9, wherein: 11. The recording apparatus according to any one of claims 1 to 10, further comprising storage means for storing a correspondence between information on the rotational speed of the rotating mirror and the rotational speed of the image carrier and the second light emission amount. The image forming apparatus according to claim 1. In the image portion, the light source is irradiated with light of the first light emission amount from the light source to adhere the developer, thereby forming the latent image.
The image forming apparatus according to any one of claims 1 to 11, wherein the light source emits light of the second light emission amount so as to prevent the developer from adhering to the non-image portion.

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