JP2012208386A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a printing time by reducing an influence of a starting time of a scanner motor on the printing time in an image forming apparatus performing calibration.SOLUTION: The image forming apparatus includes a control section 136 for controlling that a rotation speed of a laser scanner motor 204 becomes 40,000 rpm when performing the image formation. The control section 136 executes a simple calibration by rotating the laser scanner motor 204 at 20,000 rpm in which the rotation speed is slower than 40,000 rpm and a rising time is shorter than the rising time till reaching 40,000 rpm.

Description

  The present invention relates to an image forming apparatus using an electrophotographic process, and more particularly to an image forming apparatus that performs calibration such as density and registration.

  An image printed by an image forming apparatus using an electrophotographic process changes under the influence of environmental conditions such as temperature and humidity and deterioration with time of the image forming apparatus. The characteristics of an image that is likely to change include density in a black and white image, density, gradation, color reproducibility, and registration deviation amount (= color deviation amount) in a color image. In order to solve these image quality fluctuation problems, in general image forming apparatuses, before forming an image, the charging potential of the photosensitive drum, the light amount / timing applied to the photosensitive drum, the development bias, the supply of the developing toner amount, etc. The image forming conditions such as the control value are controlled. These correction operations are called calibration. By such image control, it is possible to suppress image quality fluctuation of the image forming apparatus with high accuracy and accuracy.

  However, since calibration usually takes several minutes, the problem is that the user's print waiting time is increased by performing calibration. In order to improve this problem, for example, Patent Document 1 discloses an invention in which density calibration is omitted under specific conditions. The image forming apparatus of Patent Document 1 has a non-volatile memory built in the toner cartridge, and records the time when the image forming apparatus is powered off or when the toner cartridge is last replaced. Keep it. Then, by comparing with the power-on time, the density correction detection process is not performed when the power is shut off for a short time that does not require density correction. As another solution for shortening the printing waiting time of the user by calibration, Patent Document 2 discloses an invention using a simplified calibration. The image forming apparatus disclosed in Patent Document 2 performs two types of calibrations, that is, a detailed gradation calibration with a long inspection time (= detail correction processing) and a simple gradation calibration with a short inspection time (= simple correction processing). Prepare. The number of patches in the inspection image for simple gradation calibration is configured to be smaller than the number of patches in the inspection image for detailed gradation calibration. Simple gradation calibration compares the approximate straight line from the previous calibration with the approximate straight line from the current calibration, and based on the result of this comparison, determines whether to perform detailed gradation calibration. decide. For example, if the approximate straight line at the time of the current calibration has not changed significantly from the approximate straight line at the time of the previous calibration, the gradation correction curve can be corrected appropriately by the simple gradation calibration. Do not perform gradation calibration. In this way, the time required for calibration is shortened.

JP-A-11-218972 JP 2001-309178 A

  In addition to calibration, the following has become a problem in recent years as a factor that increases the user's print waiting time. In order to increase the added value of image forming apparatuses, the printing speed is increasing year by year. In order to increase the printing speed, the rotational speed of the laser scanner motor is increased. FIG. 13 shows the rising characteristics of a laser scanner motor using a DC brushless motor. FIG. 13 is a graph with time [sec] on the horizontal axis and scanner speed (= laser scanner motor rotation speed) [rpm] on the vertical axis. For example, when the target rotational speed indicated by a broken line in FIG. 13 is 20000 rpm, the acceleration is 2.5 seconds at an acceleration of 8000 rpm / sec, and it takes 1 second for the rotation to stabilize, and 3.5 seconds is required in total. When the target rotational speed indicated by the solid line is 40000 rpm, the acceleration is performed at an acceleration of 8000 rpm / sec for 5 seconds, and it takes 1 second for the rotational speed to be stabilized, and it takes 6 seconds in total. The effect of such an increase in the rise time of the laser scanner motor on the print time will be described by taking a color laser printer that performs simple calibration with a calibration time of about 1 second as an example.

FIG. 14A is a time chart showing the operation of main control signals until the color laser printer with the laser scanner rotation speed of 20000 rpm performs simple calibration and printing. In FIG. 14A, the vertical axis represents control signals, and the horizontal axis represents the time axis. The printing time of the color laser printer shown in FIG. 14A (here, the time from receipt of a printing command to printing three sheets) is 11.0 seconds. The breakdown of printing time is as follows.
-Preparation period until the start of simple calibration Ta: 3.5 seconds-Simple calibration period Tb: 1.0 seconds-Video data generation period Tc: 3.0 seconds-Print period of 3 sheets Td: 3 .5 seconds

Next, FIG. 14B is a time chart showing the operation of main control signals until the color laser printer with the laser scanner rotation speed of 40000 rpm performs simple calibration and prints. The printing time of the color laser printer shown in FIG. 14B (here, the time from receipt of a printing command to printing of three sheets) is 13.5 seconds. The breakdown of printing time is as follows.
-Preparation period until the start of simple calibration Ta: 6.0 seconds-Simple calibration period Tb: 1.0 second-Video data generation period Tc: 3.0 seconds-Print period of 3 sheets Td: 3 .5 seconds

  The preparation period Ta until the start of simple calibration with a difference in printing time in the case of 20000 rpm and 40000 rpm will be described in detail. In the preparation period Ta until the start of the simple calibration, the following three preparations are performed.

1) Raise the photosensitive drum to the image forming speed. Thereafter, the phase of each photosensitive drum is adjusted. When the phase adjustment is completed, the photosensitive drum ready signal becomes high level (2.0 seconds in FIGS. 14A and 14B). An arrow A means that the condition is necessary to start charging output.
2) The rotational speed of the laser scanner motor is increased to the speed at the time of image formation. When the image forming speed is reached, the laser scanner ready signal becomes high level (3.5 seconds in FIGS. 14A and 14E). The arrow C means that the condition is necessary for starting the charging output.
3) The amount of transfer voltage is determined (1.5 seconds to 3.0 seconds in FIGS. 14A and 14K).
Comparing the above three, it takes the most time to start up the laser scanner motor. Accordingly, the printing time is delayed (11.0 + 2.5 = 13.5 seconds) by a difference of 2.5 seconds (= 6.0−3.5 seconds) in the startup time of the laser scanner motor.

  As described above, when the startup time of the laser scanner motor exceeds the preparation time of the photosensitive drum and the transfer voltage determination time, the excess time increases the printing time and increases the waiting time of the user. One method for shortening the startup time of the laser scanner motor is to use a multi-beam laser by increasing the number of beams. If a multi-beam laser is used, the rotational speed of the laser scanner motor can be reduced. However, this method increases the cost significantly. As another method for shortening the startup time of the laser scanner motor, there is a method for increasing the drive current of the scanner motor. However, this method can be used when each unit saves power and is used in a current capacity 15A that can be supplied from one outlet of a commercial power source for home use as in a high-speed color image forming apparatus. It becomes difficult in design to allocate a sufficient current capacity.

  An object of the present invention is to solve at least one of such problems and other problems. An object of the present invention is to shorten the printing time by reducing the influence of the startup time of the scanner motor on the printing time in an image forming apparatus that performs calibration.

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

  (1) An execution result of full calibration in which an image forming unit forms an inspection image on a conveyance belt and a detection unit detects the inspection image to correct image density or image color misregistration, or the image formation unit performs the conveyance belt. An execution result of simple calibration that forms a simple inspection image on the top and that detects the simple inspection image by the detection means and corrects image density or image color misregistration; Generation means for generating video data using the full calibration conversion table or the simple calibration conversion table based on the input image data, and a laser beam corresponding to the video data generated by the generation means On the image carrier by a rotating polygon mirror rotated by a scanner motor A latent image forming unit that forms an electrostatic latent image by inspection, and a control unit that controls the rotation speed of the scanner motor to be a first rotation speed when forming an image. The control means includes the scanner at a second rotational speed whose rotational speed is slower than the first rotational speed and whose rise time is shorter than the rise time until the first rotational speed is reached. An image forming apparatus, wherein the simple calibration is executed by rotating a motor.

  According to the present invention, in an image forming apparatus that performs calibration, the printing time can be shortened by reducing the influence of the startup time of the scanner motor on the printing time.

Schematic configuration cross-sectional view of a color laser printer of Examples 1 to 4 Block diagram of color laser printer of Examples 1 to 4 The figure which shows the test | inspection image for the density | concentration test | inspection at the time of full calibration of Examples 1-4. The figure which shows the test | inspection image for the registration test | inspection at the time of full calibration of Examples 1-4. The figure which shows the test | inspection image at the time of the simple calibration of Examples 1-4. The flowchart which shows the process which selects the calibration of Examples 1-3. Timing chart from the start of printing to execution of simple calibration in Example 1 until printing is completed Example 1 Laser Scanner Motor Startup Sequence and Graph Compared with Conventional Example Enlarged view of the inspection image of the density of Examples 1-3 The figure which shows the optical system at the time of the printing of Example 3, and a full calibration The figure which shows the optical system at the time of the simple calibration of Example 3 10 is a flowchart illustrating processing for updating a data conversion table for simple calibration according to the fourth embodiment. The figure which shows the starting time of the laser scanner motor of the conventional example Timing chart when the rotation speed of the conventional laser scanner motor is 2000 rpm and 40000 rpm

  The mode for carrying out the present invention will be described in detail below with reference to examples.

  A color laser printer, for example, which is one of the image forming apparatuses according to the first embodiment, is a 600 dpi two-beam color laser printer having a printing speed of 60 ppm (number of printed A4 sheets per minute).

<Configuration of color laser printer>
FIG. 1 is a cross-sectional view showing a schematic configuration of a color laser printer. The color laser printer 101 includes a paper feed cassette 102 on which paper 137 is placed, and a transfer belt 106 (conveyance belt). The color laser printer 101 includes photosensitive drums 111 to 114 (image carrier), charging rollers 115 to 118, laser scanners 119 to 122 (latent image forming means), and developing rollers 123 to 126. The color laser printer 101 includes a transfer roller 127 to 130, a density / registration sensor 131, a registration sensor 132 (detection unit), a fixing unit 133, a paper discharge sensor 134, a video data generation unit 135 (generation unit), and a control unit 136 (control unit). ) Etc. Further, the developing unit including the photosensitive drum 111, the charging roller 115, and the developing roller 123 is integrated into a single process cartridge 107 that can be replaced by the user. The process cartridge 107 contains yellow (Y) toner. Similarly, the process cartridge 108 contains magenta (M) toner, the process cartridge 109 contains cyan (C) toner, and the process cartridge 110 contains black (B) toner. The host computer 100 is connected to the color laser printer 101.

<Control block diagram>
FIG. 2 is a control block diagram showing the relationship between the control unit 136 and main units controlled by the control unit 136. In response to a request from the video data generation unit 135, the control unit 136 outputs the density information obtained from the density / registration sensor 131 and the registration sensor 132 and information on the registration deviation amount to the video data generation unit 135. The laser scanners 119 to 122 include a laser diode 201 and a laser driver 202 that controls a current flowing through the laser diode 201. The laser scanners 119 to 122 include a polygon mirror 203 (rotating polygonal mirror) that scans a laser beam and a laser scanner motor 204 that rotates the polygon mirror 203. Further, the laser scanners 119 to 122 include a laser scanner motor driver 205 that controls the rotational speed of a laser scanner motor 204 (scanner motor), a beam detection sensor 206 that detects a laser beam that is reciprocally scanned, and the like.

  Further, the control unit 136 includes a laser beam light quantity setting circuit 211, and the control unit 136 outputs a control signal and a PWM signal that transmits a light emission quantity to the laser driver 202 to turn on the laser diode 201. The control unit 136 outputs a control signal to the laser scanner motor driver 205 to control the rotation speed of the polygon mirror 203. The scanning speed target value switching circuit 212 switches the target value of the rotational speed of the polygon mirror 203 from, for example, 20000 rpm to 40000 rpm. The control unit 136 receives a detection signal from the beam detection sensor 206. As a result, the control unit 136 calculates the rotation speed of the polygon mirror 203 and feeds it back to the rotation control of the laser scanner motor 204. In addition, the control unit 136 detects the laser scanning position and controls the laser light emission start timing corresponding to the video data. The control unit 136 outputs a control signal to the drum motor driver 221 and rotates the drum motor 222 to control the rotational speeds of the photosensitive drums 111 to 114, the charging rollers 115 to 118, the developing rollers 123 to 126, and the transfer rollers 127 to 130. To do. The control unit 136 outputs a control signal to the high voltage generation circuit 223 to control the high voltage bias of the charging rollers 115 to 118, the developing rollers 123 to 126, and the transfer rollers 127 to 130. The control unit 136 outputs a control signal to the conveyance motor driver 224 and rotates the conveyance motor 225 to move the transfer belt 106. The control unit 136 detects a paper presence signal output from the paper discharge sensor 134 and detects that printing has been completed.

<Image formation processing>
The color laser printer 101 that has received a print command and print data (image data) from the host computer 100 forms an image as follows. The video data generation unit 135 generates video data for turning on / off the laser beam based on density information / registration information from the print data. Based on the video data generated by the video data generation unit 135, the laser scanners 119 to 122 for the respective colors expose and scan the surfaces (on the image carrier) of the photosensitive drums 111 to 114 with laser beams. Form. The electrostatic latent images on the photosensitive drums 111 to 114 are visualized as toner images by the developing rollers 123 to 126. These series of image forming operations are controlled in synchronization by the registration sensor 132 so that the image is transferred to a predetermined position of the sheet 137 to be conveyed. In the transfer nip portion, the paper 137 is transferred by superimposing toner images of yellow, magenta, cyan, and black colors. The paper 137 on which the toner image has been transferred is heated at a predetermined temperature by the fixing unit 133 and is pressed to fix the toner image, and is discharged to complete printing.

<Outline of calibration sequence>
Calibration for correcting image density and image color misregistration in the color laser printer 101 will be described. There are two types of calibration executed by the color laser printer 101. One is full calibration and the other is simple calibration. Full calibration is calibration that emphasizes accuracy. In full calibration, an inspection image is formed on the transfer belt 106 under the same conditions as in printing, and the inspection image is read by the density / registration sensor 131 and the registration sensor 132. The density / registration sensor 131 and the registration sensor 132 are configured by a light emitting source LED and a light receiving element photodiode. The density / registration sensor 131 and the registration sensor 132 irradiate the toner image on the transfer belt 106 (on the conveying belt) with light and receive reflected light. The density / registration sensor 131 detects the image density and the image position based on the amount of reflected light. The registration sensor 132 detects the position of the image based on the amount of reflected light.

  Full-calibration inspection images are shown in FIGS. FIG. 3 is an inspection image for correcting the density. In FIG. 3, the inspection image is drawn at a location that can be read by the density and registration sensor 131. In FIG. 3, 151 is a pattern image for inspecting black density and gradation, and 152 is a pattern image for inspecting cyan density and gradation. Reference numeral 153 denotes a pattern image for inspecting the density and gradation of magenta, and reference numeral 154 denotes a pattern image for inspecting the density and gradation of yellow. These pattern images (inspection images) 151 to 154 include eight gradations (for example, 151a to 151h). An arrow G indicates the conveyance direction of the transfer belt 106. In the density calibration, in order to reduce the measurement variation, the inspection image of FIG. 3 is measured three times to obtain an average value. Thereafter, an inspection image is measured for confirmation with the image whose density has been corrected.

  FIG. 4 is an inspection image for correcting registration deviation. In FIG. 4, the inspection image is drawn at a location that can be read by the density / registration sensor 131 and the registration sensor 132. In FIG. 4, reference numerals 161 and 162 denote images (hereinafter referred to as sub-scanning registration inspection images) for inspecting registration in the sub-scanning direction (conveyance direction of the transfer belt 106). In the sub-scanning registration inspection image 161, 161a, 161c, 161e, and 161g are black and are treated as a reference when compared with other colors. 161b is yellow, 161d is magenta, and 161f is cyan. Reference numerals 163 to 168 denote images (hereinafter referred to as main scanning registration inspection images) for inspecting registration in the main scanning direction (direction orthogonal to the sub-scanning direction). In the main scanning registration inspection image 163, 163a, 163c, 163e, 163g, 163h, 163k, 163n, and 163q are black and are treated as a reference when compared with other colors. 163b and 163j are yellow, 163d and 163m are magenta, and 163f and 163p are cyan. An example of a registration deviation derivation method in the main scanning direction will be described. As for the comparison between yellow and black, the distance in the sub-scanning direction between 163b and 163j for yellow and the distance in the sub-scanning direction for black 163a and 163h are compared to determine the amount of deviation in the main scanning direction. However, the influence of the shift in the sub-scanning direction is subtracted when calculating the shift in the main scanning direction. This full calibration takes 90 seconds.

  Next, simple calibration will be described. Simple calibration is a calibration intended to ensure a certain level of image quality in a short time. The time required for the simple calibration of this embodiment is 1 second. FIG. 5 shows an inspection image of simple calibration. Reference numerals 171 and 172 denote images for inspecting the magnification in the sub-scanning direction. The same applies to 173a and 175. Reference numeral 173 denotes an image for inspecting registration in the sub-scanning direction. Reference numeral 174 denotes an image for inspecting registration in the main scanning direction. Reference numeral 176 denotes an image for inspecting the density and gradation of black. Reference numeral 177 denotes an image for inspecting the density and gradation of cyan, 178 for magenta, and 179 for yellow.

<Execution sequence of full calibration and simple calibration>
The execution sequence of full calibration and simple calibration will be described with reference to the flowchart of FIG. The control unit 136 monitors whether the process cartridges 107 to 110 and the transfer belt 106 have been replaced during the power-off period or during printing standby (step (hereinafter referred to as S) 01). If the control unit 136 determines in S01 that the process cartridges 107 to 110 or the transfer belt 106 have been replaced, full calibration is executed in S03. When the control unit 136 determines that neither the process cartridge 107 to 110 nor the transfer belt 106 has been replaced in S01, the control unit 136 determines whether or not the user has instructed execution of full calibration in S02. If the control unit 136 determines in S02 that the user has instructed execution of full calibration, the control unit 136 executes full calibration in S03. The user inputs, for example, whether or not to perform full calibration using an input unit (not shown) or the host computer 100. If the control unit 136 determines in S02 that the execution of full calibration has not been instructed by the user, the control unit 136 determines whether or not a print command from the host computer 100 has been input (a print command has been generated) in S04. If the control unit 136 determines in S04 that a print command has been input from the host computer 100, it performs simple calibration in S05. In S06, the video data generation unit 135 is based on the data obtained by the simple calibration executed by the control unit 136 in S05 (hereinafter referred to as simple calibration data) (execution result) and the image data input from the host computer 100. Generate video data. In step S07, the control unit 136 forms an image based on the video data generated by the video data generation unit 135 in step S06.

  The above is the condition for executing full calibration or simple calibration in the present embodiment. However, in order to improve the accuracy of color misregistration and density misregistration, full calibration may be executed when the power is turned on. However, in this case, since the warm-up time after power-on becomes longer, the convenience for the user may be impaired.

<Simple calibration sequence>
The operation of the color laser printer 101 from the start of printing to the completion of printing after performing simple calibration will be described in detail, and the printing time of the color laser printer 101 as an effect of the present embodiment will be described. Note that the printing time is the time from the start of printing to the completion of printing after the calibration is executed.

  FIG. 7 is a timing chart from the start of printing to simple calibration until printing is completed. Hereinafter, a description will be given along the timing chart of FIG. The control unit 136 that has received the print command immediately starts the next four sequences simultaneously. The first is the startup of the photosensitive drums 111 to 114 (FIG. 7A), the second is the startup of the transfer belt 106 (FIG. 7J), and the third is the startup of the fixing unit 133 (FIG. 7). 7 (q)) and the fourth is the startup of the laser scanner motor 204 (not shown) (FIG. 7D). In the present embodiment, the above four sequences are immediately started at the same time. However, the present invention is not limited to this.

  The first drum motor 222 accelerates the photosensitive drums 111 to 114 toward the target speed, and the photosensitive drums 111 to 114 reach the target speed 1.5 seconds after the rotation starts. After each of the photosensitive drums 111 to 114 reaches the target speed, the control unit 136 executes control for adjusting the phases of the photosensitive drums 111 to 114. When the photosensitive drums 111 to 114 and the transfer belt 106 reach the target speed, the control unit 136 executes control for determining transfer voltages to be applied to the transfer rollers 127 to 130. The control for determining the transfer voltage is to determine the transfer voltage by adjusting the transfer voltage so that a predetermined transfer current flows. The transfer voltage is determined at 3 seconds (FIG. 7 (k)). Arrow B means that the determination of the transfer voltage is a necessary condition for starting the charging output. Returning to the description of the sequence of the photosensitive drums 111 to 114, the phase alignment of the photosensitive drums 111 to 114 is completed at the time of 2 seconds. After the phase alignment is completed, as shown in FIG. To high level. An arrow A means that the photosensitive drum ready signal is a condition necessary for starting charging output. The fixing unit 133 feeds power to the fixing heater and heats it to the target temperature while rotating the fixing roller (FIG. 7 (q)).

  The operation of the laser scanner motor 204 will be described with reference to FIG. FIG. 8A is a graph in which the vertical axis represents the rotational speed [rpm] of the laser scanner motor 204 and the horizontal axis represents time [sec]. The laser scanner motor 204 continues to increase the rotation speed at a constant acceleration from the start 0 seconds to 2.5 seconds toward the target speed 20000 rpm (second rotation speed) as the first stage. Thereafter, it takes 1 second to rotate at a constant speed of 20000 rpm (convergence time) and when it reaches 3.5 seconds, the scanner low-speed ready signal becomes high level as shown in FIG. Arrow C means that the scanner low-speed ready signal is a necessary condition for starting charging output. When the low-speed scanner ready signal and the photosensitive drum ready signal are at a high level and the transfer voltage is determined and these three conditions are satisfied, simple calibration is started. As described above, it is a feature of this embodiment that simple calibration is performed at 20000 rpm, which is half of the scanner motor speed of 40000 rpm (first rotation speed) during printing. The rise time until the scanner motor speed reaches 20000 rpm when performing simple calibration is shorter than the rise time until the scanner motor speed reaches 40000 rpm when performing image formation (see FIG. 8).

  The continuation of the simple calibration sequence will be described according to the time chart. First, charging of the photosensitive drums 111 to 114 is started (3.5 seconds in FIG. 7C). Subsequently, an electrostatic latent image of the inspection image of the simple calibration shown in FIG. 5 is formed on the photosensitive drums 111 to 114 by the scanner unit rotating at a constant speed of 20000 rpm (FIG. 7G). The electrostatic latent image of the inspection image of the simple calibration on the photosensitive drums 111 to 114 is developed by the developing roller 123 as shown in FIG. 7H to form a toner image. The developed toner image is transferred onto the transfer belt 106 (3.8 to 4.4 seconds in FIG. 7 (k)). The simple calibration toner images transferred onto the transfer belt 106 are sequentially read from the downstream side by the density / registration sensor 131 and the registration sensor 132 (FIG. 7M). The density and registration information read by the density / registration sensor 131 and the registration sensor 132 is output to the video data generation unit 135.

  The time required for the simple calibration is 1 second from the start of charging of the photosensitive drums 111 to 114 (3.5 seconds) to the output of information such as density and registration to the video data generation unit 135 (4.5 seconds). is there. The simple calibration toner image is cleaned and collected by a cleaning blade (not shown) and a cleaning roller (not shown). An arrow D indicates that the video data generation unit 135 starts generating video data after the simple calibration is completed. The video data generation unit 135 converts the image data input from the host computer 100 into video data based on the simple calibration data (FIG. 7 (n) and FIG. 6 S06). The simple calibration toner image (particularly density) formed in this embodiment is different from the full calibration toner image (particularly density). For this reason, image data is converted into video data using a different data conversion table depending on whether it is based on simple calibration data or based on full calibration data. Further, immediately after the completion of the simple calibration, the laser scanner motor, as shown in 4.2 seconds of FIG. 8A, sets the target rotational speed by the scanning speed target value switching circuit 212 to the rotational speed at the time of printing 40000 rpm. Set to to perform speed change.

  The generation time of video data by the video data generation unit 135 differs depending on the type and amount of image data from the host computer 100 and the data processing capability of the video data generation unit 135. In this embodiment, the generation time of the video data is 3 seconds, and the generation of the video data is completed at the time point of 7.5 seconds in FIG. Arrow E means that the generation of video data is a necessary condition for starting charging output. At this time, the rotation speed of the laser scanner motor is still being adjusted (see FIG. 8A).

  In FIG. 7F, the scanner full speed ready signal becomes high level at 7.7 seconds. In this embodiment, the waiting time for the rise of the scanner from the completion of the generation of the video data (7.5 seconds) until the scanner full speed ready signal becomes high level (7.7 seconds) is 0.2 seconds. The arrow F means that the scanner full speed ready signal is a necessary condition for starting the charging output. The electrostatic latent image can be formed on the photosensitive drums 111 to 114 by the laser scanner, and as soon as video data of the electrostatic latent image is ready, the control unit 136 starts image formation of the video data. First, the photosensitive drums 111 to 114 are charged (7.7 to 10.7 seconds in FIG. 7C), and electrostatic latent images are formed on the charged photosensitive drums 111 to 114 with a laser beam (FIG. 7 (p) )). Thereafter, the electrostatic latent image is developed as a toner image on the photosensitive drums 111 to 114 by the developing rollers 123 to 126 (7.9 to 10.9 seconds in FIG. 7H). Then, the toner images are sequentially transferred and superimposed on the paper 137 conveyed by the transfer belt 106 (8.0 to 11.0 seconds in FIG. 7K).

  The sheet 137 with the transferred toner image is conveyed to the fixing unit 133 and fixed to the sheet 137 by heat and pressure. Thereafter, the paper 137 passes through the paper discharge sensor 134 and is discharged to the paper discharge tray at the top of the color laser printer 101. Printing is thus completed (8.3 to 11.2 seconds in FIG. 7 (r)). Therefore, the printing time of this embodiment (the time from the start of printing until calibration is completed after printing is started) is 11.2 seconds. Compared with the conventional example shown in FIG. 14A, the printing time of this embodiment is shortened by 2.3 seconds (= 13.5-11.2 seconds).

<Printing time reduction mechanism>
The mechanism by which the printing time of this embodiment can be shortened by 2.3 seconds compared to the conventional example will be described in detail. In the present embodiment, as the first period Ta, the preparation time until the simple calibration is started requires 3.5 seconds. As the second period Tb, one second is required for the simple calibration. As the third period Tc, it takes 3 seconds to generate video data. As the fourth period Td, it takes 0.2 seconds to wait for the laser scanner full speed ready signal. As the fifth period Te, it takes 3.5 seconds to print three sheets. The total is 11.2 seconds (= 3.5 + 1.0 + 3.0 + 0.2 + 3.5 seconds). The simple calibration time is 1 second in FIGS. 14A and 7 and does not contribute to time reduction. Further, since the image formation time is 3.5 seconds in both FIG. 14A and FIG. 7, it does not contribute to time reduction. The reason for shortening the printing time in this embodiment is that, as shown in FIG. 8A, the simple calibration and the start-up time of the laser scanner motor can be executed simultaneously for 0.3 seconds. Even during the execution of the simple calibration, if the formation of the electrostatic latent image of the inspection image is completed as shown in FIG. 7G, the rotation speed of the laser scanner motor 204 may be accelerated from 20000 rpm to 40000 rpm. .

Similarly, the video data generation time and the start-up time of the laser scanner motor can be executed simultaneously for 3 seconds. Further, as an extension factor, as shown in FIG. 8B, in the two-stage start-up of the laser scanner motor 204 executed in this embodiment, the waiting time (= convergence time) until the laser scanner motor 204 is stabilized is laser. One more time than when the scanner motor 204 is started at once. For this reason, the total startup time of the laser scanner motor 204 is increased (increased by 1 second). Summing up the above shortening factors and extension factors,
0.3 (shortening) +3.0 (shortening) -1.0 (extending) = 2.3 seconds (shortening)
It becomes. Therefore, this embodiment is established under the following conditions.
(Time when the second laser scanner motor start-up time and simple calibration are executed in parallel) + (Time when the second laser scanner motor start-up time and video data generation time are executed in parallel)> ( (Laser scanner motor convergence time)

  As described above, in this embodiment, the simple calibration is executed by driving the laser scanner motor at a low-speed rotation with a fast startup time of the laser scanner motor 204. Thereafter, the printing time can be shortened by performing in parallel the start-up step of causing the laser scanner motor to reach the rotation speed at the time of printing and the step of starting the image formation of the print image such as video data generation.

  In this embodiment, the video data generation is started after the simple calibration is completed. However, in the effect of the present embodiment, the period in which the second laser scanner motor startup time and the video data generation time are executed in parallel is important. Therefore, part of the video data generation is performed before the end of the simple calibration. You may have started. In this embodiment, the rotation speed of the laser scanner motor 204 during the simple calibration is 50% of the full speed. However, the rotation speed of the laser scanner motor 204 at the time of the simple calibration can be carried out even if it is other than 50%. In this embodiment, the simple calibration time is 1 second. However, as already described, the simple calibration time is not essentially related to the effect of this embodiment. Even if the simple calibration time is 3 minutes, the printing time can be shortened by 2.3 seconds compared to the conventional case by adopting this embodiment. Therefore, this embodiment can be applied to all image forming apparatuses that execute calibration at a rotational speed lower than the rotational speed of the laser scanner motor at the time of printing.

  The transfer method of the color laser printer 101 of this embodiment is a method of transferring from the photosensitive drums 111 to 114 to the paper 137. However, an image forming apparatus that performs calibration can also be realized in an image forming apparatus that performs secondary transfer onto a sheet via an intermediate transfer member as a conveyance belt or an intermediate transfer belt.

  As described above, according to the present embodiment, in the image forming apparatus that performs calibration, it is possible to reduce the influence of the startup time of the scanner motor on the printing time and to shorten the printing time.

  The second embodiment shows an example in which the amount of laser light at the time of the simple calibration described in the first embodiment is increased. When the density patch 151h at the time of full calibration in Example 1 is enlarged, black toner is formed over the entire area as shown in FIG. 9A (= 256 gradation FFs (= 256)). Further, when the density patch 176c at the time of the simple calibration is enlarged, it is as shown in FIG. 9B. It is a halftone image with two horizontal lines and two spaces.

  As a method for expanding a density patch density range by writing a blank (= space) portion during simple calibration with a laser beam, there is a method of increasing the laser light amount and increasing the beam diameter of the laser beam. When the laser beam diameter is increased 1.5 times from FIG. 9B, it can be as shown in FIG. 9C. Increasing the amount of laser light is achieved by increasing the amount of current flowing through the laser diode. As shown in FIG. 9C, when the laser light amount is constantly increased, the light amount of the overlapping portion of the two beams increases. In order to alleviate this, there is a method of periodically increasing the laser light quantity as shown in FIG. In FIG. 9D, the phase for increasing the light amount of the first laser beam is shifted from the phase for increasing the light amount of the second laser beam. That is, the light amounts of the first laser beam and the second laser beam are periodically changed, and the phases of the periodic changes of the first laser beam and the second laser beam are made different. As described above, the feature of this embodiment is that the amount of laser light is increased during the simple calibration. Since the laser light quantity other than the laser light quantity at the time of simple calibration is the same as that of the first embodiment, description of the simple calibration sequence of this embodiment will be omitted.

  As described above, in this embodiment, when the laser scanner motor 204 is driven at a low speed, the amount of laser light is increased to reduce the decrease in the inspection image density. In addition, in this embodiment, after the latent image of the inspection image for simple calibration is written, the start-up process in which the laser scanner motor 204 reaches the rotation speed at the time of printing and the start of image formation of the print image such as video data generation are started. The processes performed until then are performed in parallel. Thereby, the printing time can be shortened. In this embodiment, a color laser printer using a two-beam laser has been described as an example. However, the configuration of this embodiment is effective regardless of the number of laser beams.

  As described above, according to the present embodiment, in the image forming apparatus that performs calibration, it is possible to reduce the influence of the startup time of the scanner motor on the printing time and to shorten the printing time.

  The third embodiment shows an example in which the scanner unit is characterized to extend the laser beam width during the simple calibration in the sub-scanning direction. In the second embodiment, in order to form toner in the entire area at the time of simple calibration, a laser beam having a double beam diameter must be emitted with a one-beam laser, and a laser beam with a triple beam diameter must be emitted with a two-beam laser. Could not be realized. The present embodiment relates to an image forming apparatus capable of forming an inspection image in which toner is attached to the entire area during simple calibration.

<Configuration of laser scanner unit>
FIG. 10 is a diagram showing the laser scanner 119 (or 120, 121, 122) and the photosensitive drum 111 (or 112, 113, 114) of this embodiment. FIG. 10A is a three-dimensional image diagram, and FIG. 10B is a simplified diagram viewed from the side. The two-beam laser diode 391 in FIG. 10 emits a laser beam. The cylindrical lens 392 is a lens that makes the laser beam horizontal. The expansion lens 393 is a lens used for simple calibration. The extended lens 393 in FIG. 10 is out of the laser beam path. The polygon mirror 203 has six surfaces. The laser scanner motor 204 rotates the polygon mirror 203. The f-θ lens 396 is for making the laser scanning speed constant on the photosensitive drums 111 to 114. The folding mirror 397 reflects the laser beam and irradiates the photosensitive drum 111.

  The laser beam at the time of full calibration and printing is irradiated radially from the two-beam laser diode 391 as shown in FIG. 10B and becomes parallel light by the cylindrical lens 392. The parallel laser beam is reflected so as to be scanned by the polygon mirror 203, passes through the f-θ lens 396, is reflected by the folding mirror 397, and is applied to the photosensitive drum 111. On the other hand, in the laser scanner 119 during the simple calibration, the support member that holds the expansion lens 393 is pushed up by a solenoid (not shown). The extended lens 393 pushed up is inserted into the laser optical path between the cylindrical lens 392 and the polygon mirror 203. This state is shown in FIG. This is a feature of this embodiment.

<Extended lens>
The operation of the expansion lens 393 will be described. The expansion lens 393 of the present embodiment spreads the laser beam twice in the sub scanning direction. The expansion rate of the laser beam is determined by the reciprocal of the ratio of the rotational speed of the laser scanner motor 204 during simple calibration to the rotational speed during printing. The rotation speed of the laser scanner motor 204 at the time of printing and simple calibration in this embodiment is the same as that of the first embodiment (rotation speed at printing 40000 rpm, rotation speed at simple calibration 20000 rpm). Accordingly, 20000/40000 = 0.5, and the reciprocal of 0.5 is 2. As shown in FIG. 11B, the laser beam at the time of simple calibration is irradiated radially from a two-beam laser diode 391 and becomes parallel light by a cylindrical lens 392. The parallel laser beam is expanded in the sub-scanning direction by the extension lens 393, reflected so as to be scanned by the polygon mirror 203, passes through the f-θ lens 396, is reflected by the folding mirror 397, and is reflected by the photosensitive drum. 111 is irradiated.

<Density patch>
The density patch of this embodiment will be described. In the enlarged view of the density patch 351h at the time of full calibration, as shown in FIG. 9E, black toner is formed over the entire region (= 256 gradation FF (= 256)). In the enlarged view of the density patch 376c of the simple calibration, as shown in FIG. 9 (f), the entire area is formed with a low density toner. Therefore, the variation of the measurement result of the density measurement is smaller in the simple calibration of the present embodiment than in the simple calibration of the first embodiment. Except for the expansion of the laser beam at the time of simple calibration, the present embodiment is the same as the first embodiment, and therefore the description of the simple calibration sequence is omitted.

  As described above, in this embodiment, when the laser scanner motor 204 is driven at a low speed, the laser beam is spread by the expansion lens 393 so that toner can be formed in the entire region. In addition, in this embodiment, after the electrostatic latent image of the inspection image for simple calibration is written, the start-up process for reaching the rotation speed of the laser scanner motor 204 at the time of printing and the print image generation such as video data generation are performed. The steps performed until the start of image formation are performed in parallel. Thereby, the printing time can be shortened. In this embodiment, the laser light amount at the time of simple calibration is the same as the laser light amount at the time of printing. However, the laser light quantity may be increased in combination with the configuration of the second embodiment. When the amount of laser light is increased, the measurement result of simple calibration can be brought close to the measurement result of full calibration. In this embodiment, the extension lens 393 is arranged in the laser beam path between the cylindrical lens 392 and the polygon mirror 203. For example, an extension lens having the same function and a different shape is arranged in another laser beam path. Also good.

  As described above, according to the present embodiment, in the image forming apparatus that performs calibration, it is possible to reduce the influence of the startup time of the scanner motor on the printing time and to shorten the printing time.

  Embodiment 4 describes an image forming apparatus in which a data conversion table for converting image data into video data can be updated based on simple calibration data. Since the schematic configuration of the present embodiment is the same as that of the first embodiment, description thereof is omitted.

<Data conversion table update sequence>
The present embodiment will be described with reference to the flowchart of the update sequence of the data conversion table for simple calibration shown in FIG. The processing from S11 to S13 is the same as the processing from S01 to S03 in FIG. The control unit 136 executes the simple calibration of S14 following the full calibration of S13. Here, in order to improve measurement accuracy, the simple calibration may be executed a plurality of times to calculate the average value. In S15, the control unit 136 compares the execution result of the full calibration and the execution result of the simple calibration to obtain a difference. Then, the control unit 136 updates the data conversion table by adding the difference obtained from the comparison result to the data conversion table for simple calibration. Thus, the update of the data conversion table for simple calibration is completed. That is, the data conversion table for simple calibration is updated in accordance with the execution of full calibration. Since the process of S16-S19 is the same as the process of S04-S07 of Example 1, description is abbreviate | omitted.

  Thus, in an image forming apparatus capable of performing full calibration and simple calibration, it is possible to update the data conversion table for simple calibration by taking correlation data. Except for the update of the data conversion table for simple calibration, the present embodiment is the same as the first embodiment, and therefore the description of the simple calibration sequence is omitted. In addition, the simple calibration can be configured as in the second and third embodiments.

  As described above, in this embodiment, simple calibration is performed using a data conversion table that is updated as appropriate. Then, the printing time can be shortened by performing in parallel the start-up step of causing the laser scanner motor to reach the rotation speed at the time of printing and the step of starting the image formation of the print image such as video data generation. .

  As described above, according to the present embodiment, in the image forming apparatus that performs calibration, it is possible to reduce the influence of the startup time of the scanner motor on the printing time and to shorten the printing time.

106 Transfer belts 111 to 114 Photosensitive drums 119 to 122 Laser scanner 135 Video data generation unit 136 Control unit 203 Polygon mirror 204 Laser scanner motor

Claims (9)

An execution result of full calibration for forming an inspection image on the conveyance belt by the image forming unit and detecting the inspection image by the detection unit and correcting the image density or image color deviation, or the image forming unit on the conveyance belt by the image forming unit An execution result of a simple calibration that forms a simple inspection image compared to a full calibration inspection image, detects the simple inspection image by the detection means, and corrects image density or image color deviation, and an input Generating means for generating video data using the full calibration conversion table or the simple calibration conversion table based on image data;
A latent image forming means for forming an electrostatic latent image by scanning a laser beam corresponding to the video data generated by the generating means on the image carrier with a rotating polygon mirror rotated by a scanner motor;
An image forming apparatus comprising:
A control means for controlling the rotation speed of the scanner motor to be the first rotation speed when performing image formation;
The control means rotates the scanner motor at a second rotation speed that is lower than the first rotation speed and shorter than the rising time until the rising time reaches the first rotation speed. And performing the simple calibration.   The controller switches the rotation speed of the scanner motor from the second rotation speed to the first rotation speed when the latent image forming means finishes forming the simple electrostatic latent image of the inspection image. The image forming apparatus according to claim 1.   The generation means generates video data while the control means is controlled so that the rotation speed of the scanner motor is changed from the second rotation speed to the first rotation speed. The image forming apparatus according to claim 1.   The control means includes: a time until the scanner motor reaches the first rotation speed from the second rotation speed and a time during which the simple calibration is executed in parallel; and The sum of the time until the first rotation speed is reached from the second rotation speed and the time when the generation of the video data by the generation means is executed in parallel is determined by the convergence time of the scanner motor. 2. The image forming apparatus according to claim 1, wherein the simple calibration is executed by rotating the scanner motor at the second rotation speed when the value is larger. 3.   The image forming apparatus according to claim 1, wherein the control unit increases a light amount of laser light when the simple calibration is executed. The laser beam has a first laser beam and a second laser beam,
The control means periodically changes the light amounts of the first laser beam and the second laser beam and makes the phase change phase of the first laser beam and the second laser beam different from each other. The image forming apparatus according to claim 5. Expanding means for expanding the laser beam in the sub-scanning direction;
The image forming apparatus according to claim 1, wherein the control unit moves the expansion unit onto an optical path of the laser beam when the simple calibration is executed. The extension means is an extension lens;
The image forming apparatus according to claim 7, wherein the expansion lens has a magnification that is a reciprocal of a ratio of the second rotation speed to the first rotation speed.   The control means executes the simple calibration following the execution of the full calibration, and updates the conversion table of the simple calibration based on the execution result of the full calibration and the execution result of the simple calibration. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed.

Images