JP2004109621A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately controlling paper carriage at low costs independently of the responsiveness of a sensor by stopping a sheet of paper after moving it by a prescribed distance by using a motor such as a stepping motor whose rotational amount is digitally changed for the drive of a registration against conventional registration drive control in which the drive of the registration is stopped in accordance with a sensor arranged in the vicinity of the registration. <P>SOLUTION: The image forming apparatus is provided with a reference signal generation means for generating a reference signal which is general reference for the control of image formation, an exposure means for forming an electrostatic image on a photoreceptor by exposing and scanning the surface of the photoreceptor and a paper carriage means for carrying a sheet of paper to be used for transferring a toner image formed on a toner image holding means to a sheet of paper. After the lapse of prescribed time from the generation of the reference signal, paper carriage is started and the paper carriage means is stopped in accordance with a prescribed distance from the start of paper carriage. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, for example, used in a color copying machine.
[0002]
[Prior art]
A description will be given of the alignment between a sheet and a toner image when a toner image of a conventional copying machine is transferred to a sheet. A latent image is formed on the photosensitive drum in accordance with a predetermined reference signal, and the latent image is visualized by developing with a toner. This visualized toner image is held by the image carrier. The toner image held on the image carrier is transferred onto a sheet.However, conventionally, the sheet is stopped by a registration roller of a sheet feeding device, and the registration roller is driven according to the predetermined reference signal. The registration roller is driven and controlled so that the toner image on the image carrier is transferred to a predetermined position on the sheet. As for the timing of stopping the registration roller, control is performed to stop the registration roller after a predetermined time has elapsed after detecting the trailing edge of the sheet by a registration sensor disposed near the registration roller.
[0003]
FIG. 1 is a conventional paper feed timing diagram. When an ITOP-A (201) described later is input, the paper feed motor (202) is rotated after a predetermined time. In the figure, reference numeral 207 denotes a motor drive sequence with the vertical axis representing the motor drive frequency and the horizontal axis representing time. After a predetermined time, the paper supply solenoid (204) is turned on for a predetermined time, and one sheet of paper in the paper cassette is fed. The fed paper reaches a registration sensor (210) through a paper feeding conveyance path by a paper feeding motor (202) and is fed to a registration roller. Then, a predetermined registration loop amount is formed, and after a predetermined timing, the sheet feeding motor (202) stops. Further, after a predetermined timing from the above-mentioned ITOP-A (201), the driving of the sheet feeding motor (202) and the registration motor (203) is started so that the toner image on the image carrier can be transferred to a predetermined position on the sheet. The paper is transported. Here, the timing at which the registration motor (203) is stopped is controlled so as to stop the registration motor after a predetermined tm (212) time from the timing when the paper detection signal 211 of the paper feed sensor 205 changes from the presence of paper to the absence of paper. Do. Therefore, since the stop control of the registration motor is performed in accordance with the signal of the registration sensor 210, when the speed is increased, it is necessary to use an expensive sensor that responds at a high speed.
[0004]
[Problems to be solved by the invention]
However, when the above-described registration roller control is performed, when the sheet feeding speed becomes high, the precision of the control time from sensor detection to motor stop must be increased. If this is the case, there is a problem that the response time of the lever is slow and an expensive optical sensor or the like must be used, which increases the cost. Further, the same problem arises in increasing the number of prints per unit time by shortening the distance between the papers as much as possible when performing continuous paper feeding. According to the present invention, the conventional registration drive control stops the registration drive according to a sensor arranged in the vicinity of the registration, whereas the registration drive uses a motor such as a stepping motor for digitally determining the rotation amount. Then, an object of the present invention is to provide an image forming apparatus capable of performing accurate paper transport control at low cost regardless of the response of a sensor by stopping the paper after moving the paper by a predetermined amount.
[0005]
[Means for Solving the Problems]
In an electrophotographic image forming apparatus for developing an electrostatic image on a photosensitive drum into a toner image and transferring the toner image onto copy paper to form an image,
First reference signal generating means serving as all references for control of image formation,
Exposure means for forming an electrostatic image on the photoconductor by exposing and scanning the photoconductor,
A second reference signal generating means which is a horizontal synchronization signal generated from the exposure means,
A toner image holding unit for holding the developed toner image,
Paper transport means for transporting paper for transferring the toner image of the toner image holding means to the paper,
By generating an exposure start timing after a first predetermined time from the first reference signal and generating a sheet conveyance timing after a second predetermined time from the first reference signal, synchronization of the toner image and the sheet conveyance is synchronized. Having image position synchronization means for transferring the toner image to a predetermined position on the paper,
An image forming apparatus according to claim 1, wherein said sheet conveying means is stopped in accordance with a predetermined distance after the start of driving of said sheet conveying means.
[0006]
As described above, the present invention can be summarized into the following configuration by organizing and summarizing the present invention.
[0007]
(1) In an electrophotographic image forming apparatus for developing an electrostatic image on a photosensitive drum into a toner image and transferring the toner image onto copy paper to form an image,
Reference signal generating means serving as all references for controlling image formation;
Exposure means for forming an electrostatic image on the photoconductor by exposing and scanning the photoconductor,
A toner image holding unit for holding the developed toner image,
Paper transport means for transporting paper for transferring the toner image of the toner image holding means to the paper,
The paper conveyance is started after a predetermined time from the reference signal, the toner image is transferred to a predetermined paper area, and the paper conveyance unit is stopped according to a predetermined distance from the start of the paper conveyance. Image forming apparatus.
[0008]
(2) The image forming apparatus according to the above (1), wherein a stepping motor is used as a drive source of the sheet conveying means.
[0009]
(3) The image forming apparatus according to (2), wherein the predetermined distance after the start of the driving of the sheet conveying means is such that a stop pulse or a deceleration timing is generated by counting a driving pulse of a stepping motor.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 is a configuration diagram of a full-color printer which is an example of the image forming apparatus according to the present invention.
[0011]
Reference numeral 100 denotes a copying apparatus main body; and 400, a circulating automatic document feeder (hereinafter referred to as RDF) for automatically feeding a document. When a plurality of documents are stacked upward, the document is at the bottom. They are read in order from the object.
[0012]
Hereinafter, the operation of the image forming apparatus of the present embodiment will be described.
[0013]
In FIG. 2, reference numeral 101 denotes a document table glass serving as a document table, and reference numeral 102 denotes a document illumination lamp which constitutes a scanner together with a scanning mirror 103. The scanner is reciprocally scanned in a predetermined direction by a motor (not shown), and the reflected light of the original is transmitted through the lens 107 via the scanning mirrors 103 to 105 to form an image on the CCD sensor 108.
[0014]
Reference numeral 117 denotes a laser, which irradiates the photosensitive drum 1 with a laser beam converted into an electric signal by the image sensor unit 106 and modulated based on an image signal subjected to predetermined image processing by the image control unit 139.
[0015]
A photoconductor drum (hereinafter, simply referred to as “photoconductor”) 1 as an image carrier is provided so as to be rotatable in the direction of arrow A by a motor (not shown). Around the photoconductor 1, a primary charger 7, an exposure device 117, a color developing unit 13, a black developing unit 14, a transfer charger 10 and a cleaner device 12 are arranged.
[0016]
The color developing unit 13 includes three developing devices 13Y, 13M, and 13C for color development. The developing devices 13Y, 13M, and 13C develop the latent images on the photoconductor 1 with Y, M, and C toners, respectively. When developing the toner of each color, the developing unit 13 is rotated in the direction of arrow R by a motor (not shown), and the developing device of the color is aligned so as to contact the photoconductor 1.
[0017]
In the development of black toner used for full-color and black monochrome images, the latent image is developed with black toner by the black developing device 14.
[0018]
The toner images of each color developed on the photoreceptor 1 are sequentially transferred to a belt 2 as an intermediate transfer body by a transfer device 10, and four color toner images are superimposed. The belt 2 is stretched around rollers 17, 18, 19, 170, 180. Among these, the roller 17 is coupled to a driving source (not shown) to function as a driving roller for driving the belt 2, the roller 18 functions as a tension roller for adjusting the tension of the belt 2, and the roller 19 functions as a secondary transfer device Function as a backup roller for the transfer roller 21 of FIG.
[0019]
A belt cleaner 22 is provided at a position facing the roller 17 with the belt 2 interposed therebetween, and residual toner on the belt 2 is scraped off by a blade.
[0020]
The recording paper pulled out from the recording paper cassette 122 to the transport path by the pickup roller 123 is fed to the nip portion, that is, the contact portion between the secondary transfer device 21 and the belt 2 by the pair of rollers 138 and 126. The toner image formed on the belt 2 is transferred onto the recording paper at the nip portion, is thermally fixed by the fixing device 150, and is discharged out of the device.
[0021]
The fixing device 150 includes three rollers of upper and lower two rollers and an external heating roller. Two heaters of an upper heater 132 are inserted in an upper roller, and a lower heater 133 is inserted in a lower roller. An external heater 141 is inserted into the heating roller 140. The output of the upper thermistor 134 pressed against the surface of the upper roller, the lower thermistor 135 pressed against the surface of the lower roller, and the output of the external thermistor 142 on the surface of the external roller cause a heater (not shown). The control unit controls ON / OFF of the upper heater 132, the lower heater 133, and the external heater 141 to keep the temperature of the roller surface constant. The toner is fixed by pressure and heat in the fixing device 150, and is discharged out of the main body by the discharge roller 131.
[0022]
In the color printer having the above configuration, an image is formed as follows. First, a voltage is applied to the charging device 7 to uniformly negatively charge the surface of the photoconductor 1 at a predetermined charging portion potential. Subsequently, exposure is performed by an exposure device 117 including a laser scanner so that the charged image portion on the photoconductor 1 has a predetermined exposure portion potential, thereby forming a latent image. The exposure device 117 forms a latent image corresponding to an image by turning on and off based on the image signal.
[0023]
A developing bias preset for each color is applied to a developing roller of the developing device 13Y or the like, and the latent image is developed with toner when passing through the position of the developing roller, and is visualized as a toner image. The toner image is transferred to the belt 2 by the transfer device 10, further transferred to recording paper by the secondary transfer device 21, and then sent to the fixing device 150. During full-color printing, four color toners are superimposed on a belt and then transferred to recording paper. The toner remaining on the photoreceptor 1 is charged by a preliminary cleaning device so that the toner is easily cleaned, and is removed and collected by a cleaner device 12. Finally, the photoreceptor 1 is uniformly removed by a static eliminator (not shown). The charge is removed to around 0 volts to prepare for the next image forming cycle.
[0024]
The image forming timing of the color printer is controlled based on a predetermined position on the belt 2. The belt 2 is stretched around rollers including a driving roller 17, a tension roller 18, and a backup roller 19, and a predetermined tension is given by the tension roller 18.
[0025]
Between the driving roller 17 and the roller 19, reflection sensors 160 and 161 for detecting a reference position are arranged. The reflection sensors 160 and 161 detect a marking on a reflection tape or the like provided at the end of the outer peripheral surface of the belt 2 and output an image top signal (hereinafter referred to as an ITOP signal).
[0026]
The outer peripheral length of the photoconductor 1 and the peripheral length of the belt 2 are in an integer ratio represented by 1: n (n is an integer). With this setting, the photoconductor 1 rotates an integer while the belt 2 makes one revolution, and returns to the same state as before the one revolution of the belt, so that when the four colors are superimposed on the intermediate transfer belt 2, In this case (the belt makes four revolutions), it is possible to avoid color shift due to uneven rotation of the photoconductor 1.
[0027]
In the intermediate transfer type image forming apparatus as described above, after detecting the ITOP-A signal (176), the exposure is started by the exposure device 117 including a laser scanner after a predetermined time has elapsed. Further, as described above, while the belt 2 makes one rotation, the photoconductor 1 rotates an integer and returns to the same state as before the one rotation of the belt, so that a toner image is always formed on the belt 2 at the same position. After the four color toner images are transferred to the intermediate transfer member and the images are superimposed on each other, a predetermined sheet of paper in the paper cassette 122 is fed after a predetermined time has elapsed based on the ITOP signal of the final color. By transferring the superimposed toner image, a color image is formed on a sheet. After that, the toner image on the paper is fixed by heat and pressure by the fixing device 150 to form a permanent color image on the paper. ITOP-B (175) is used when two toner images are formed on the intermediate transfer member 2.
[0028]
Output of a black (BK) image as an example of the image output in FIG. 2 is performed as follows. First, a voltage is applied to the charging device 7 to uniformly negatively charge the surface of the photoconductor 1 at a predetermined charging portion potential. Subsequently, exposure is performed by an exposure device 117 including a laser scanner so that the charged image portion on the photoconductor 1 has a predetermined exposure portion potential, thereby forming a latent image. The exposure device 117 forms a latent image corresponding to an image by turning on and off based on the image signal.
[0029]
A developing bias preset for each color is applied to a developing roller of the BK developing device 14 or the like, and the latent image is developed with toner when passing through the position of the developing roller, and is visualized as a toner image. The toner image is transferred to the belt 2 by the transfer device 10, further transferred to recording paper by the secondary transfer device 21, and then sent to the fixing device 150. During full-color printing, four colors of toner are superimposed on a belt and then transferred to recording paper. The toner remaining on the photoreceptor 1 is charged by a preliminary cleaning device so that the toner is easily cleaned, and is removed and collected by a cleaner device 12. Finally, the photoreceptor 1 is uniformly removed by a static eliminator (not shown). The charge is removed to around 0 volts to prepare for the next image forming cycle.
[0030]
The image forming timing of the color printer is controlled based on ITOP-A (176).
[0031]
Next, the control timing of the color printer having the above configuration is shown in FIG. First, when a start signal is input to the CPU (174) (501), a rotation signal (MOTOR-ON) 173 of the drum motor is output and rotated at a predetermined rotation speed (502). When the rotation of the drum motor is stabilized, the drum motor outputs a DRUM-LOK signal (172) indicating the operating state at the target rotation speed to the CPU (503). When the DRUM-LOK signal is input to the CPU, the ITOP input is enabled, and the input of the ITOP-A (176) is waited (504). Thereafter, when ITOP-A is input to the CPU (505), the image forming operation is started, the pre-exposure is turned on (507), the grid high voltage is turned on (508), and a latent image can be written on the photoconductor. State. After a predetermined time, the BK developing high voltage is output (509). Then, after a predetermined time, the rotation of the sleeve of the BK in the developing zone is started (510). In this state, the latent image on the photosensitive drum can be developed into a toner image. Therefore, a predetermined latent image is formed on the photosensitive member by the laser, developed, and a visible image is formed by the toner. Thereafter, before the visible image on the photoconductor reaches the primary transfer position after a predetermined time, the primary transfer is output (512). When the primary transfer is output, the toner image on the photosensitive drum is transferred to the intermediate transfer member. Further, the toner image on the intermediate transfer member is transferred to the paper in the paper cassette. At this point, the paper in the paper cassette is fed and transported to the registration position. This is performed by controlling the operation of the paper feed motor (514) and the paper feed solenoid (516). Then, the secondary transfer high voltage is output before the image on the intermediate transfer body reaches the secondary transfer position (513). Thereafter, the sheet at the registration position is transported to the secondary transfer position so that the toner image on the intermediate transfer body can be transferred to the sheet. This is performed by controlling the registration motor (515) and the paper feed motor (514). Further, the rotation speed of the intermediate transfer member and the paper conveyance speed are controlled to be the same at the time of transfer of the toner image. The toner image thus transferred onto the paper is subjected to heat and pressure through a fixing device to become a permanent image. FIG. 4 is a paper feed timing diagram of the present invention. When ITOP-A (301) is input, the paper feed motor (302) is rotated after a predetermined time. In the figure, reference numeral 307 denotes a motor drive sequence with the vertical axis representing the motor drive frequency and the horizontal axis representing time. After a predetermined time, the paper feed solenoid (304) is turned on for a predetermined time, and one sheet of paper in the paper cassette is fed. Then, the fed paper reaches a paper feed sensor (310) through a paper feed path by a paper feed motor (302) and is fed to a registration roller. Then, a predetermined registration loop amount is formed, and after a predetermined timing, the sheet feeding motor (302) stops. Further, after a predetermined timing from the above-mentioned ITOP-A (301), the driving of the sheet feeding motor (302) and the registration motor (303) is started so that the toner image on the image carrier can be transferred to a predetermined position on the sheet. The paper is transported. Here, as the timing for stopping the registration motor (303), the number of drive pulses of the registration motor is counted, and control is performed so as to output a predetermined paper transportable pulse. The registration motor drive control for the Pm (311) pulse in FIG. 4 is performed.
[0032]
FIG. 5 shows a control flow of the registration motor. First, when the registration motor is turned on (step 601), the registration motor is started up to speed 1 and constant speed driving is performed at speed 1 (step 602). At this point, pulse counting is started simultaneously with driving of the registration motor, and integration of motor drive pulses is performed (step 603). Then, it is determined whether or not a predetermined timing before the sheet is brought into contact with the image carrier from the start of the motor drive (step 604). When a predetermined speed switching timing comes, the speed is decreased from speed 1 to speed 2 and constant speed driving is performed at speed 2. Thereafter, the sheet is conveyed at a speed 2 to transfer the toner image on the image carrier onto the sheet. Then, it is determined whether a motor drive pulse corresponding to the transport amount of the sheet at which the predetermined transfer is completed has been reached (step 606). When the registration motor is driven by a predetermined number of pulses, the registration motor is stopped (step 607). When the registration motor is conveyed by a predetermined sheet conveyance amount and stopped in this way, it is not necessary to perform the registration motor control in accordance with the sensor in the conveyance path, so that the speed can be easily increased.
[0033]
【The invention's effect】
According to the present invention, the conventional registration drive control stops the registration drive according to a sensor arranged in the vicinity of the registration, whereas the registration drive uses a motor such as a stepping motor for digitally determining the rotation amount. Then, when the paper is moved by a predetermined amount and stopped, accurate paper conveyance control can be performed at low cost regardless of the response of the sensor.
[0034]
[Brief description of the drawings]
FIG. 1 is a conventional paper feed timing diagram. FIG. 2 is a configuration diagram of a full-color printer which is an example of an image forming apparatus according to the present invention. FIG. 3 is a control timing diagram of a color printer. FIG. FIG. 5: Control flow of the register motor [Explanation of reference numerals]
1 photoreceptor drum 2 belt (intermediate transfer member)
7 Primary charger 10 Transfer charger (transfer device)
REFERENCE SIGNS LIST 12 Cleaner device 13 Color developing unit 14 Black developing units 17, 18, 19, 170, 180 Roller 21 Secondary transfer device (transfer roller)
22 Belt Cleaner 100 Copying Machine Main Body 101 Document Placement Table 102 Document Illumination Lamps 103 to 105 Scanning Mirror 106 Image Sensor 107 Lens 108 CCD Sensor 117 Laser (Exposure Device)
122 Recording paper cassette 123 Pick-up roller 126, 138 Roller pair 131 Ejection roller 132 Upper heater 133 Lower heater 134 Upper thermistor 135 Lower thermistor 140 External heating roller 141 External heater 142 External thermistor 150 Fixing device 160, 161 Reflective sensor 175 ITOP-B Signal 176 ITOP-A signal 201 ITOP-A
202 feed motor 203 registration motor 204 feed solenoid 205 feed sensor 207 motor drive sequence 210 registration sensor 211 paper detection signal 212 tm
400 Recirculating Automatic Document Feeder (RDF)

Claims (3)

In an electrophotographic image forming apparatus for developing an electrostatic image on a photosensitive drum into a toner image and transferring the toner image onto copy paper to form an image,
Reference signal generating means serving as all references for controlling image formation;
Exposure means for forming an electrostatic image on the photoconductor by exposing and scanning the photoconductor,
A toner image holding unit for holding the developed toner image,
Paper transport means for transporting paper for transferring the toner image of the toner image holding means to the paper,
The paper conveyance is started after a predetermined time from the reference signal, the toner image is transferred to a predetermined paper area, and the paper conveyance unit is stopped according to a predetermined distance from the start of the paper conveyance. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein a stepping motor is used as a driving source of the sheet conveying unit. 3. The image forming apparatus according to claim 2, wherein the predetermined distance after the start of the driving of the sheet conveying means is such that a stop pulse or a deceleration timing is generated by counting a driving pulse of a stepping motor.

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