KR100572293B1 - Image forming device - Google Patents

Abstract

In the electrophotographic image forming apparatus, productivity can be improved by shortening the time from the completion of the first transfer of the toner image from the photosensitive member to the intermediate transfer member to the start of the second transfer of the toner image from the intermediate transfer member to the sheet. To be. Therefore, when the sheet to which the toner image is secondarily transferred from the intermediate transfer member 205 is a predetermined sheet, after the primary transfer of the toner image from the photosensitive drum 202 to the intermediate transfer member 205, The rotational speed is changed from the first speed to the second speed, and the speed change of the intermediate transfer member 205 is performed within one rotation in which the primary transfer is performed according to the image forming mode, or the primary transfer is performed. It decides whether to perform in 1 rotation following 1 rotation.

Transfer member, photosensitive drum, color image reader, image forming apparatus, control unit

Description

Image forming apparatus {IMAGE FORMING DEVICE}

The present invention relates to an image forming apparatus which firstly transfers an intermediate transfer member formed on a photosensitive member, and then secondarily transfers a toner image on the intermediate transfer member onto a recording sheet.

In recent years, electrophotographic image forming apparatuses which first transfer the toner image formed on the photosensitive member to the intermediate transfer member and then secondarily transfer the toner image on the intermediate transfer member to the recording sheet have been spreading. In such an image forming apparatus, when the distance between the secondary transfer unit and the fixing unit is short, the recording sheet may be caught by the secondary transfer unit and the fixing unit, so that the rotational speed of the intermediate transfer member and the rotational unit of the fixing unit during secondary transfer are limited. In other words, it is necessary to match the fixing speed.

On the other hand, in the case of forming an image on a recording sheet such as thick paper, an envelope, or OHP, the fixing speed for plain paper is insufficient, and therefore, it is necessary to set the fixing speed slower than the fixing speed of plain paper. In this case, as described above, the rotational speed of the intermediate transfer member must also be low in accordance with the fixing speed, so that the productivity is reduced when the image is formed on a recording sheet such as thick paper, an envelope, or an OHP.

Moreover, the image forming apparatus which rotates an intermediate | middle transfer body at a predetermined speed at the time of a primary transfer, decelerates the rotational speed of an intermediate transfer body to a fixing speed immediately after completion | finish of primary transfer, and performs secondary transfer is proposed. (See, for example, Patent Document 1). According to this, the fall at the time of primary transfer can be suppressed.

[Patent Document 1] Japanese Patent Application Laid-Open No. 4-67174

However, in the conventional image forming apparatus as described above, in order to reduce the rotational speed of the intermediate transfer member immediately after the primary transfer is completed, the time from the deceleration of the intermediate transfer body to the start of the secondary transfer is long, thereby improving productivity. It was disturbing.

Further, Japanese Patent Laid-Open No. 9-146434 discloses that the distance between the primary transfer portion and the secondary transfer portion in the intermediate transfer member is longer than the maximum image length, and after completion of the primary transfer, on the intermediate transfer member The image forming apparatus starts to decelerate the rotational speed of the intermediate transfer member when the image leading edge reaches a predetermined distance from the secondary transfer position, and deceleration is completed before the image leading edge on the intermediate transfer member reaches the secondary transfer position. It is.

However, in such an image forming apparatus, it is assumed that the distance between the primary transfer portion and the secondary transfer portion in the intermediate transfer member is equal to or greater than the distance added to the maximum image length for the deceleration of the intermediate transfer member. . Therefore, in order to enable image formation of a longer image, it is proposed to further lengthen the distance between the primary transfer portion and the secondary transfer portion in the intermediate transfer member.

However, there is an image forming apparatus in which the distance between the primary transfer portion and the secondary transfer portion in the intermediate transfer member cannot be lengthened due to the configuration of the image forming apparatus. There is also an image forming apparatus which forms a plurality of images on one circumference of an intermediate transfer member in recent years. In such an image forming apparatus, depending on the size of the image or the number of images formed on one circumference of the intermediate transfer member, the deceleration and the case where deceleration can be completed before the image tip on the intermediate transfer member reaches the secondary transfer position are performed. You may not be able to complete it. Therefore, if secondary image transfer is always performed when the image leading end portion of the intermediate transfer member reaches the secondary transfer portion after completion of the primary transfer, the secondary transfer is started before the deceleration of the intermediate transfer member is completed. There may be a problem that the secondary transfer is performed in a state where the rotation speed is faster than the fixing speed.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of improving productivity by shortening the time from completion of primary transfer to start of secondary transfer. .

1 is a cross-sectional view showing the overall configuration of an outline of a color image forming apparatus according to the present invention.

2 is a block diagram showing the detailed configuration of a digital image processing unit.

3 is a block diagram showing the configuration of image information processing.

4 is a block diagram showing a main configuration of a control unit.

5 is a perspective view showing the configuration of the light-writing optical system.

Fig. 6 is a timing chart showing an image forming operation in which two sheets of plain paper of a comparative example are attached.

7 is a flowchart showing an image forming operation to which two thick sheets of comparative example are attached.

8 is a flowchart showing an operation for calculating the time from the completion of the first transfer to the start of deceleration of the motor speed.

Fig. 9 is a timing chart showing a bottom image forming operation in which two pieces of thick paper are attached.

Fig. 10 is a timing chart showing an image forming operation in which two pieces of thick paper are attached.

Fig. 11 is a timing chart showing an image forming operation in which one piece of thick paper is attached.

Fig. 12 is a timing chart showing an image forming operation in which one piece of thick paper is attached.

<Explanation of symbols for the main parts of the drawings>

1: color image reader

2: color image printer

50: image forming apparatus

100: control unit

102: automatic document feeder

113: digital image processing unit

116: external interface

201: Laser Scanner

202: photosensitive drum

203: each developer

204: primary transfer roller

205: intermediate transcript

206: secondary transfer roller

207: Pressure Roller

208 to 211: cassette

212 to 215: pickup roller

220: manual feed roller

221 to 224: developer

230: Cleaning Blade

231: Blade

233: first discharge roller

234: second discharge roller

235: Reverse Roller

236: third discharge roller

237: first badge flapper

238: second badge flapper

239: Third Badge Flapper

240: manual sheet tray

261 to 264: Feeding Roller

265 to 268: vertical pass conveying roller

269: registration roller

270: HP Detection Sensor

271: home position seal

301: CPU

302: memory

303: control panel

304: ROM

305: RAM

800: motor

The image forming apparatus of the present invention is configured as follows to achieve the above object.

(1) a photosensitive member carrying a toner image, a rotatable intermediate transfer member onto which the toner image on the photosensitive member is transferred, primary transfer means for primaryly transferring the toner image on the photosensitive member to the intermediate transfer member, and on the intermediate transfer member A secondary transfer means for secondaryly transferring a toner image onto a sheet, and a control means for controlling the intermediate transfer member and the secondary transfer means, wherein the control means is a predetermined sheet, the intermediate after the primary transfer. The rotational speed of the transfer body is changed from the first speed to the second speed, and the control means performs the speed change of the intermediate transfer body within one rotation in which the primary transfer is performed according to the image forming mode. And determining whether the first transfer is performed within one rotation following the one rotation performed.

(2) The image forming apparatus according to (1), wherein the predetermined sheet is any one of a thick paper, an envelope, a postcard, an OHP sheet, a label sheet, a tab sheet, and a second original sheet.

(3) The image forming apparatus according to (1), wherein the image forming mode includes the number of toner images transferred on one circumference of the intermediate transfer member.

(4) The image forming apparatus according to (1), wherein the image forming mode includes a size of a toner image.

(5) The control means determines whether the first distance between the leading end portion of the toner on the intermediate transfer member on the intermediate transfer member and the secondary transfer means is longer than a predetermined distance at the completion point of the primary transfer, The image forming apparatus according to (1), wherein the speed change is performed in one rotation in which the first transfer is performed or in one rotation following the first rotation in which the first transfer is performed.

(6) The image according to (5), wherein the control means performs a speed change of the intermediate transfer member within one rotation in which the first transfer is performed when the first distance is longer than the predetermined distance. Forming device.

(7) The control means, when the first distance is less than or equal to the predetermined distance, changes the speed of the intermediate transfer member within one revolution following the first revolution in which the primary transfer is performed (5) The image forming apparatus described in the above.

(8) further comprising a fixing means for fixing the toner image on the sheet at the fixing speed after the second transfer, wherein the control means controls the speed of the intermediate transfer member to be substantially the same as the fixing speed. The image forming apparatus according to (1).

(9) The image forming apparatus according to (1), wherein the first speed is higher than the second speed.

(10) The image according to (1), wherein the intermediate transfer member has a mark for detecting a leading end portion of the toner on the intermediate transfer member, and further has detection means for detecting a mark of the intermediate transfer member. Forming device.

(11) The image forming apparatus according to (10), wherein the control means changes the speed of the intermediate transfer member immediately before the detection means detects a mark of the intermediate transfer member.

EMBODIMENT OF THE INVENTION Hereinafter, the color image forming apparatus 50 which is one Embodiment of this invention is demonstrated with reference to drawings.

In each figure, the member which attached | subjected the same reference number shall represent the same member, and overlapping description is abbreviate | omitted.

1 is a schematic sectional view of a color image forming apparatus 50.

In the figure, reference numeral 1 denotes a color image reader unit (hereinafter referred to as "leader unit 1"), and 2 denotes a color image printer unit (hereinafter referred to as "printer unit 2").

Reference numeral 100 denotes a control unit, 101 a platen glass (platen), 102 an automatic document feeder (ADF), 103 and 104 a light source for illuminating the original, and 105 and 106 are reflective bevel portions.

Reference numerals 107 to 109 denote mirrors, 110 denotes lenses, and 111 denote CCDs.

Reference numeral 112 denotes a substrate and 113 denotes a digital image processing unit.

Reference numeral 114 denotes a carriage that accommodates the light sources 103 and 104, the reflective bevel portions 105 and 106, and the mirror 107, and 115 denotes a carriage that accommodates the mirrors 108 and 109.

Reference numeral 116 denotes an external interface (I / F) with another device.

Next, the configuration of the printer unit 2 will be described.

Reference numeral 200 denotes a rotating shaft, 201 denotes a laser scanner as a latent image forming means, 202 denotes a photosensitive drum as a photosensitive member, and 203 denotes a color developing device comprising a developing means and a developing switching means.

The laser scanner 201, the photosensitive drum 202, and each color developing unit 203 constitute image forming means.

Reference numeral 204 denotes a primary transfer roller.

Reference numeral 205 denotes an intermediate transfer member, 206 denotes a secondary transfer roller, 207 denotes a pressurized roller, 208, 209, 210, and 211 denotes a cassette, 212, 213, 214, 215 denotes a pickup roller, and 220 denotes a manual feed roller, 221, 222, 223 and 224 are developing units, 230 are cleaning blades, 231 are blades, 232 are waste toner boxes, 233 are first discharge rollers, 234 are second discharge rollers, 235 are reverse rollers, 236 are third discharge rollers, and 237 are made of 1 exit flapper, 238 is the second exit flapper, 239 is the third exit flapper, 240 is the manual sheet tray, 261, 262, 263, 264 is the feed roller, 265, 266, 267, 268 is the vertical pass conveying roller, 269 is A registration roller, 270 is an HP detection sensor, and 271 is a home position (HP) seal.

The image forming apparatus 50 has a reader portion 1 at the top and a printer portion 2 at the bottom.

The structure of the reader part 1 is demonstrated.

The reader section 1 has a platen glass (platen) 101 and an automatic document feeder (ADF) 102. Instead of the automatic document feeder 102, a configuration in which a mirror platen or a white platen (not shown) may be attached.

As the light sources 103 and 104 for illuminating the original, a light source of a kind such as a halogen lamp, a fluorescent lamp, a xenon tube lamp, or the like is used.

Light from the light sources 103 and 104 is focused on the original on the platen glass 101 by the reflective bevel portions 105 and 106.

The reflected light or the projection light from the original on the platen glass 101 is condensed on the CCD (charge coupled element) image sensor (hereinafter referred to as CCD) 111 by the lens 110.

The CCD 111 is mounted on the substrate 112. The controller 100 controls the entire image forming apparatus. As shown in Fig. 2, the digital image processing unit 113 includes the clamp & amp & s / h & a / d units 502 to the foundation removing unit 515 except for the CCD 111 and the external I / F 116. ) And a binary conversion unit 401 and a delay unit 402 as shown in FIG.

The carriage 114 houses the light sources 103 and 104, the reflective bevel portions 105 and 106, and the mirror 107. The carriage 115 accommodates mirrors 108 and 109.

In addition, the carriage 114 at the speed V, the carriage 115 at the speed V / 2, and mechanically in the sub-scan direction Y orthogonal to the electrical scanning direction (the main scan direction X) of the CCD 111. By moving, the whole surface of the original on the platen glass 101 is scanned.

The external interface I / F 116 is an interface with another device, for example a personal computer or a network.

2 is a block diagram showing the detailed configuration of the digital image processing unit 113. As shown in FIG.

In the figure, reference numeral 502 denotes a clamp & amp & S / H & A / D section, 503 a shading section, 504 a connection & MTF correction & document detection section, 505 an input masking section, 506 a selector, and 507 a color space compression. & BASE REMOVAL & LOG CONVERTER, 508 DELAY, 509 MOARE REMOVAL, 510 VARIATION PROCESSOR, 511 UCR & MASKING & BLACK CHARACTER REFLECTION, 512 CORRECTION, 513 FILTER, 514 is a base removing unit, and 515 is a black character determination unit.

The light from the light sources 103 and 104 is reflected by the original on the platen glass 101, and the reflected light is guided to the CCD 111 and converted into an electric signal (when the CCD 111 is a color sensor, RGB Although the color filter of the color filter is placed inline on the one-line CCD in inline order, it is also possible to arrange the R filter, the G filter, and the B filter for each CCD by the three-line CCD. It may be different from the configuration.

The electrical signal (analog image signal) is input to the digital image processing unit 113, sample-held (S / H) by the clamp & AMP & S / H & A / D unit 502, and dark of the analog image signal. The level is clamped to the reference potential, amplified to a predetermined amount (the above processing order is not limited to the notation in order), and then A / D converted to, for example, a digital signal of 8 bits each of RGB.

This RGB signal is a shading unit 503, and after shading correction and black correction are performed, the connection & MTF correction & document detection unit 504, for example, when the CCD 111 is a 3-line CCD, Since the processing differs in the read position between the lines, the delay amount is adjusted for each line according to the read speed, and the signal timing is corrected so that the read positions of the three lines are the same.

Since the MTF correction changes the MTF of the reading according to the reading speed or the variation ratio, the change is corrected so that the original detection detects the original size by scanning the original on the platen glass 101.

The digital signal whose read position timing is corrected is corrected by the input masking unit 505 to correct the spectral characteristics of the CCD 111 and the spectral characteristics of the light sources 103 and 104 and the reflective bevel portions 105 and 106.

The output of the input masking unit 505 is input to the selector 506 switchable with the external I / F signal.

The signal output from the selector 506 is input to the color space compression & base removal & LOG converter 507 and the base removal unit 514.

After the base input is removed, the signal input to the base removing unit 514 is input to the black character determination unit 515 that determines whether or not the original in the original is black text, and generates a black text signal from the original.

In the color space compression & base elimination & LOG conversion unit 507 where the output of another selector 506 is input, the color space compression determines whether or not the read image signal is within a range that can be reproduced by the printer. If not, leave it as it is. If not, correct it so that the image signal is within the range that can be reproduced by the printer.

Then, the base removing process is performed, and the LOG converting unit converts the RGB signal from the YMC signal.

The timing of the output signal of the color space compression & base elimination & LCG converter 507 is adjusted by the delay unit 508 to correct the signal and timing generated by the black character determination unit 515.

The two types of signals are removed by the moire removal unit 509 and subjected to the shift processing in the main scanning direction by the displacement processing unit 510.

The signal processed by the shift processing unit 510 is a UCR & masking & black character reflecting unit 511. From the YMC signal, a YMCK signal is generated by UCR processing, and the masking processing unit corrects the signal at the output of the printer. The determination signal generated by the black character determination unit 515 is fed back to the YMCK signal.

The signal processed by the UCR & masking & black character reflecting unit 511 is density-adjusted by the gamma correction unit 512 and then smoothed or edged by the filter unit 513.

The signal thus processed is transmitted to the printer unit 2.

3 is a diagram showing a process of receiving, at the printer unit 2, a signal processed by the digital image processing unit.

The 8-bit multi-valued signal is converted into a binary signal by the binary conversion unit 401.

The conversion method at this time may be any of the dither method, the error diffusion method, and the error diffusion improvement.

The converted binary signal is transmitted to the external I / F 116 and the delay unit 402.

The external I / F 116 transmits the received signal to an external output device such as FAX (not shown) as needed.

Since the delay unit 402 corrects the received signal and the laser emission timing of the laser scanner unit 201, the delay unit 402 adjusts the transmission timing to the laser scanner unit 201.

Then, it transmits to the laser scanner unit 201.

The binary conversion unit 401 and the delay unit 402 may be configured to be included in the digital image processing unit 113.

4 is a block diagram illustrating the configuration of main parts of the control unit 100.

Reference numeral 218 denotes a printer control I / F, 301 denotes a type of sheet, a CPU for reducing the rotational speed of the intermediate transfer member 205 and a conveyance speed of the sheet before secondary transfer, and 302 stores the size of the sheet to form an image. Memory 303 is an operation unit (operation panel), 304 is ROM, and 305 is RAM.

The control unit 100 has a CPU 301 having an I / F which exchanges information for performing control with respect to the digital image processing unit 113, the printer control I / F 218 and the external I / F 116, respectively. And an operation unit 303 and a memory 302.

The memory 302 is composed of a RAM 305 that provides a work area for the CPU 301 and a ROM 304 that stores a control program of the CPU 301.

Moreover, the operation part 303 is comprised by the liquid crystal with a touch panel for input of the process execution content by an operator, information about the process with respect to an operator, and notification of a warning.

Next, the configuration of the color printer unit 2 will be described with reference to FIGS. 1 and 5.

The control unit 100 receives the control signal from the CPU 301 of the control unit 100 described above to the printer control I / F 218 and operates the printer unit 2 based on the control signal from the printer control I / F 218. do.

5 is a diagram illustrating a schematic configuration of the laser scanner 201.

Reference numeral 601 denotes a laser driver circuit board, 602 denotes a collimator lens, 603 denotes a cylindrical lens, 604 denotes a polygon mirror, 605 denotes a polygon mirror driving motor, 606 denotes an imaging lens, 607 denotes a reflective mirror, and 608 denotes a BD (beam detector) circuit board. .

The laser light corresponding to the image data signal is emitted by the laser driver circuit board 601 and the laser light converted into parallel light by the collimator lens 602 and the cylindrical lens 603 is transferred to the polygon mirror driving motor 605. This is incident on the polygon mirror 604 rotating at a constant speed.

The laser light reflected from the polygon mirror 604 passes through the imaging lens 606 and the reflection mirror 607 disposed before the polygon mirror 604, and scans in the main scanning direction to irradiate the photosensitive drum 202.

The photosensitive drum 202 rotates in a counterclockwise direction, and an electrostatic latent image is formed on the photosensitive drum 202 by the laser scanner 201.

The rotary color developer 203 is configured by arranging the developer 221, 222, 223, and 224 corresponding to each color of black, yellow, magenta, and cyan in the clockwise direction around the rotation shaft 200. The developing units 221, 222, 223, and 224 develop by attaching toner on an electrostatic latent image formed on the photosensitive drum 202. FIG. The developer is not limited to toner but may be other developer.

In the embodiment, the developing devices 221 to 224 are configured to be easily detachable from the rotating color developing device 203, and the developing devices 221 to 224 of each color are mounted at positions of the designated color.

When forming a toner image on the photosensitive drum 202, only the black developing unit 221 is used to develop an ebony image, and the rotating color of the developing sleeve of the black developing unit 221 is opposed to the photosensitive drum 202. The toner according to the amount of potential formed between the surface of the photosensitive drum 202 on which the electrostatic latent image is exposed and the surface of the developing sleeve to which the developing bias is applied is splashed from the developer 221 to the surface of the photosensitive drum 202 by rotating the developing device 203. An electrostatic latent image on the surface of the drum 202 is developed.

In the case of forming a color image, by rotating the rotating color developing unit 203, a stepping motor (not shown), the predetermined developing units 221 to 224 are alternately rotated according to the respective resolution colors to be developed. After the rotation operation is performed at the developing position close to (or contacting) the photosensitive drum 202 around the center of 200, development is performed.

Toner is supplied from the developing units 221 to 224 in accordance with the charge on the photosensitive drum 202 to develop an electrostatic latent image on the photosensitive drum 202.

The photosensitive drum 202 on which the toner image is formed is rotated in the clockwise direction, and the toner image on the photosensitive drum 202 is primarily transferred by the primary transfer roller 204 to the intermediate transfer member 205 rotating in the counterclockwise direction. Primary transfer is performed by the CPU 301 controlling the bias voltage of the primary transfer roller 204.

In the case of a full color image, since the primary transfer is performed by the intermediate transfer member 205 one by one, the primary transfer for the full color image is completed by performing the first transfer to the intermediate transfer member 205 four times.

When the intermediate transfer member 205 forms an image having a specific sheet size, for example, A4 size or less, an image of two sides (for two pages) can be formed on the intermediate transfer member 205.

On the other hand, from each cassette (first-stage cassette 208, second-stage cassette 209, third-stage cassette 210, fourth-stage cassette 221) to each pickup roller 212, 213, 214, 215 of each cassette, The sheet picked up by and conveyed by the sheet feeding rollers 261, 262, 263, and 264 of each cassette is conveyed to the registration roller 269 by the vertical path conveying rollers 265, 266, 267, and 268.

In the case of manual feeding, the sheet stacked on the manual sheet tray 240 is conveyed to the registration roller 269 by the manual feeding roller 220.

And the sheet | seat is conveyed to the nip part of the intermediate | middle transfer body 205 and the secondary transfer roller 206 at the timing which transfer to the intermediate | middle transfer body 205 is complete | finished.

Thereafter, the sheet is conveyed in the direction of the fixing unit 207 in the form of being fitted to the secondary transfer roller 206 and the intermediate transfer member 205 and simultaneously compressed to the intermediate transfer member 205 and on the intermediate transfer member 205. The toner image is secondarily transferred to the sheet by the secondary transfer roller 206. Secondary transfer is performed by the CPU 301 controlling the bias voltage of the secondary transfer roller 206.

The toner image transferred to the sheet is heated and pressed by the fixing roller and the pressure roller 207 to be fixed to the sheet.

In addition, with regard to the transfer residual toner on the intermediate transfer member 205 remaining without being transferred to the sheet, the cleaning blade 230 capable of contacting and spaced apart on the surface of the intermediate transfer member 205 is rubbed, and the transfer residual toner is intermediate. By scraping off the surface of the transfer member 205, it is cleaned by post-processing control later in the image forming sequence.

In the photosensitive drum unit, the residual toner is scraped off from the drum surface by the blade 231, and is conveyed to the waste toner box 232 integrated in the photosensitive drum unit.

Further, the secondary transfer positive bias and the secondary transfer reverse bias are alternately applied to the residual toner of each positive polarity on the surface of the secondary transfer roller which is likely to be adsorbed unexpectedly, and onto the intermediate transfer member 205. The residual toner is completely cleaned by adsorbing the residual toner of each polarity on the surface, and scraping the residual toner by the intermediate transfer cleaning blade 230, thereby completing the post-processing control.

When the sheet on which the image is fixed is the first discharge medium, the first discharge flapper 237 is switched in the direction of the first discharge roller 233, and discharged toward the first discharge roller 233.

In the case of the second discharge medium, the first discharge flapper 237 and the second discharge flapper 238 are switched in the second discharge roller direction 234 and discharged with the target of the second discharge roller 234.

In the case of the third discharge medium, the first discharge flapper 237 and the second discharge flapper 238 are switched in the direction of the reverse roller 235 in order to perform the reverse operation by the reverse roller 235. Invert to).

After reversing with the reversing roller 235, the third discharge flapper 239 is switched in the direction of the third discharge roller 236 and discharged with the aim of the third discharge roller 236.

In the case of the double-sided discharge, similarly to the case of the third discharge, the reversal operation is performed by the reverse roller section 235, the third discharge flapper 239 is switched in the direction of the double-sided unit, and conveyed to the double-sided unit.

After the sheet is detected by the double-sided sensor, the sheet is stopped once after a predetermined time, fed again as soon as the image is ready, and the second surface is formed.

Next, image formation control in consideration of productivity, which is a feature of the present embodiment, will be described with reference to FIGS. 6 to 12 together with a comparative example.

First, the image forming control of the comparative example will be described.

(Image Forming Control in First Comparative Example)

Fig. 6 is a diagram showing a timing chart of image formation with two plain papers of the comparative example attached.

Reference numeral 701 denotes a speed change timing of the DC brushless motor 800 that drives the photosensitive drum 202 and the intermediate transfer member 205. When printing plain paper, rotate it at the speed (V1) for producing plain paper.

Reference numeral 702 denotes an HP signal for determining the image tip timing, which is output whenever the home position (LIP) seal 271 mounted inside the intermediate transfer member 205 is detected by the HP detection sensor 270.

Reference numeral 703 denotes a timing at which the laser emits light based on the image data, and light emission starts after a predetermined time elapses from the HP signal 702. This is done for each color to form a color image with little color shift. Here, two images corresponding to A4 size are simultaneously formed, and the first image, Y-B, M-B, C-B, and K-B, in which two sheets of Y-A, M-A, C-A, and K-A are attached, shows the second image. Note that the attachment of two pieces means the transfer of two pages of images onto one circumference of the intermediate transfer member 205.

Reference numeral 704 denotes a timing at which the toner image formed on the photosensitive drum 202 is first transferred to the intermediate transfer member 205.

Reference numeral 705 denotes a timing for rotating the rotary color developer (hereinafter referred to as rotary rotary) 203 so as to bring the other developer closer to the photosensitive drum 202.

Reference numeral 706 denotes a timing at which the toner image transferred on the intermediate transfer member 205 is secondarily transferred onto the sheet, and the timing can be determined based on the HP signal 702.

Reference numeral 707 denotes a period from latent image formation to secondary transfer.

When the number of image formation sheets is one, only the laser and primary transfer of YA, MA, CA, and KA, and the secondary transfer of A are controlled out of the timing 706 of the secondary transfer, and the number of image formation is three or more. In this case, the control of the period 707 is repeated.

Reference numerals 710, 711, 712, and 713 denote time from each of the HP signals 730, 731, 732, and 733 to the laser emission start timing.

Reference numeral 714 is a time from the HP signal to the start of the second transfer.

Reference numerals 720, 721, 722, and 723 denote the time from the HP signals 730, 731, 732, and 733 to the laser emission start timing of the second image with two sheets attached thereto.

Reference numeral 724 denotes the time from the HP signal to the start of the second transfer of the second image with two sheets attached.

Reference numerals 730 to 734 denote respective HP signals.

(Image Forming Control in Second Comparative Example)

Next, Fig. 7 shows a timing chart of a full color image when the type of sheet is thick paper, an envelope, or the like.

Fig. 7 is a diagram showing a timing chart of planar formation with two thick papers of the comparative example, showing an example in which the motor speed is reduced to V2 (<V1) immediately after completion of the first transfer.

Reference numerals 735 and 736 denote respective HP signals.

Up to the first transfer end timing is the same as the control timing of the plain paper.

When the type of the sheet is thick paper, an envelope, or the like, the CPU 301 takes the transfer speed of the sheet and the speed of the intermediate transfer member 205 in constant velocity in consideration of the transfer efficiency at the time of secondary transfer and the fixability at the time of fixing. The control is lowered to 1/2 of V1.

In the case of Fig. 7, immediately after the end of the primary transfer K-B, the speed of the motor is reduced to the speed V2 = V1 / 2 for the production of thick paper.

After the motor speed is stabilized at the speed V2, after a predetermined time 714 from the timing at which the HP signal is detected again, the toner image on the intermediate transfer member 205 is secondarily transferred to the sheet to be conveyed. In the example shown in Fig. 7, the rotational speed of the intermediate transfer member 205 up to secondary transfer changes as a result depending on the image size and the number of images on the circumference of the intermediate transfer member 205. However, although the CPU 301 controls the timing of the secondary transfer in response to the HP signal 735, the rotation speed of the intermediate transfer member 205 until the secondary transfer is not determined.

When the number of image formation is three or more, after transferring the image of B at the second transfer timing 706, the motor speed is accelerated again to V1 and the timing 705 for rotating the developing rotary 203 is obtained. Rotate to the yellow development position.

In the case of an ebony image, only the secondary transfer of A is controlled among the laser and the primary transfer of the KA at the timing 703 of the laser emission and the timing of the primary transfer 704 and the timing of the second transfer 706. Becomes

In forming a full color image, when only one sheet can be formed on one circumference of the intermediate transfer member 205, such as a sheet whose length is longer than A4 or a short side of letter size, the laser is emitted. At the timing 703 and the timing 704 to be primary transferred, only the secondary transfer of A is controlled from the laser and primary transfer of YA, MA, CA, and KA, and the timing 706 of secondary transfer.

In the timing chart shown in Fig. 7, productivity is the inverse of the cycle 707 from the detection of the yellow image formation timing HP to the detection of the third yellow image formation timing HP.

In the case of improving the productivity, the shortening is difficult because it depends on the size of the sheet and the method of attachment during the first and second transfers in the cycle 707.

On the other hand, the time from the completion of the primary transfer to the detection of the secondary transfer HP is irrelevant to the sheet size, and can be shortened as soon as the rotation speed of the intermediate transfer member 205 is controlled.

(Image Formation Control in the Embodiment)

Next, the image forming control of this embodiment will be described.

In the image forming control of the present embodiment, in the case of forming an image on plain paper, the control of the first comparative example described using Fig. 6 described above is performed to form an image on a thick paper, a seal, or an OHP sheet (transparent sheet for overhead projector). In the case of decelerating the rotational speed of the intermediate transfer member 205 during image formation, a predetermined time t_intvl has elapsed in accordance with the sheet size in consideration of the motor deceleration time t_v rather than immediately after the completion of the first transfer. Thereafter, the rotation speed of the intermediate transfer member 205 is decelerated.

Fig. 8 is a diagram showing a flowchart for calculating the time t_intvl from the first transfer completion timing to the start of deceleration of the motor speed to V2. The time t_intvl based on this flowchart is calculated before the first transfer.

First, the time t_1 from the HP detection timing of the intermediate transfer member 205 to the start of the first transfer in step 1001, the time t_v required to decelerate the intermediate transfer member 205 from the speed V1 to the speed V2, and the intermediate transfer. The time t_itb required for the carcass 205 to travel at the speed V1, the time t_itb 'required for the intermediate transfer body circumference including the transition from the speed V1 to the speed V2, and the sheet were returned at the speed V1. The time t_pap from the sheet front end to the rear end at the time and the time t_x of the two image intervals when two sheets are attached are calculated or stored in advance.

Since the time t_itb 'includes the transition from the speed V1 to the speed V2 compared to the time t_itb, the time becomes slightly longer.

Next, the number of images to be formed simultaneously on the intermediate transfer member 205 is determined (step 1002). When the two sheets are attached, the process proceeds to step 1003. Otherwise, the procedure goes to step 1004.

That is, the CPU 301 determines the number of rotations of the intermediate transfer member 205 up to the secondary transfer in accordance with the number of toner images formed on one circumference of the intermediate transfer member 205, and determines the timing of the secondary transfer. In accordance with this, the deceleration start timing of the intermediate transfer member 205 after the primary transfer is controlled. In other words, the CPU 301 performs the speed change of the intermediate transfer member 205 within one rotation in which the first transfer is performed or in one rotation following the first rotation in accordance with the image forming mode. Control is performed by determining.

In step 1003, the time t_1 + t_pap x 2 + t_x between the detection of the HP of the intermediate transfer member 205 and the completion of the first transfer is completed, and the speed of the motor is reduced from V1 to V2. The time t_img which totaled the time t_v is computed, and it compares with the time t_itb which the intermediate | middle transfer body 205 rounds at speed V1 (step 1005).

If t_img < t_itb ', that is, the time t_img is shorter than the time t_itb', the process proceeds to step 1007. If t_img &gt; t_itb ', that is, the time t_img is equal to or longer than the time t_itb', the process proceeds to step 1008.

Fig. 9 shows a timing chart of image formation of &quot; two sheets attached &quot; and &quot; t_img &lt; t_itb '&quot;, and Fig. 10 shows a timing chart of image formation of &quot; two sheets attached &quot; and &quot; t_img &gt; t_itb' &quot; It is a figure.

In step 1007, if the motor speed is reduced to V2 immediately after completion of the first transfer, it is suitable for the HP 734. As shown in Fig. 9, the HP 734 is used as the reference signal for the second transfer start timing.

Then, t_intvl = t_itb '-t_img, and the intermediate transfer member 205 for the time t_intvl corresponding to the sheet size and the number of images formed on one circumference of the intermediate transfer member 205 from the first transfer completion timing. It rotates to V1 and decelerates the intermediate transfer body 205 to V2 after t_intvl passes. That is, the CPU 301 determines that the primary transfer of the final color (black) and the deceleration of the intermediate transfer member 205 are performed while the intermediate transfer member 205 is rotated one time, and accordingly the intermediate after the primary transfer is finished. The deceleration start timing of the transfer member 205 is controlled so that secondary transfer is possible immediately after completion of the deceleration. As a result, the deceleration to V2 of the intermediate transfer member 205 is completed until the detection of the HP 734. In other words, the CPU 301 sets the timing of deceleration immediately before the start of the second transfer within the time from the end of the first transfer to the start of the second transfer. In accordance with the detection of the HP 734, the CPU 301 starts the driving of the registration roller 269 to feed the recording sheet to the unit portion of the secondary transfer roller 204 and the intermediate transfer member 205. Then, the CPU 301 controls the bias voltage of the secondary transfer roller 206 so as to start secondary transfer at the timing at which the image leading end on the intermediate transfer member 205 passes the secondary transfer position. As a result, the time until the detection of the HP 734 is shortened, which results in shortening the cycle 707 and improving productivity.

On the other hand, in step 1008, even if the motor speed is reduced to V2 immediately after completion of the first transfer, it is not suitable until the detection of the HP 734. As shown in Fig. 10, the HP 735 is used as the reference signal for the second transfer start timing. In this case, the image tip on the intermediate transfer member 205 passes through the secondary transfer position from the completion of the primary transfer until the detection of the HP 735, but at this timing, the CPU ( 301 controls the bias voltage of the secondary transfer roller 206.

Then, t_intvl = t_itb + t_itb '-t_img, and during the time t_intvl corresponding to the sheet size or the like from the first transfer completion timing, the intermediate transfer member 205 is rotated to V1, and then reduced to V2 to decelerate. . That is, the CPU 301 determines that the primary transfer of the final color (black) and the deceleration of the intermediate transfer member 205 are performed while the intermediate transfer member 205 is rotated two times, and accordingly the intermediate after the completion of the primary transfer is completed. The deceleration start timing of the transfer member 205 is controlled so that secondary transfer is possible immediately after completion of the deceleration. In other words, when the CPU 301 determines that the speed of the intermediate transfer member 205 cannot be changed within one rotation in which primary transfer of the final color (black) is performed, the speed change of the intermediate transfer member 205 is changed. Is controlled to be performed in one rotation following the one rotation in which the primary transfer is performed. As a result, the deceleration to V2 of the intermediate transfer member 205 is completed until the detection of the HP 735. In accordance with the detection of the HP 735, the CPU 301 starts the driving of the registration roller 269, thereby feeding the recording sheet to the nip of the secondary transfer roller 204 and the intermediate transfer member 205. Then, the CPU 301 controls the bias voltage of the secondary transfer roller 206 so that the image leading end on the intermediate transfer member 205 starts secondary transfer at a timing passing through the secondary transfer position. As a result, the time until the detection of the HP 735 is shortened, which results in shortening the cycle 707 and improving productivity.

That is, the CPU 301 causes the first transfer to be performed while rotating the intermediate transfer member 205 at the first speed, and if the distance between the image leading end and the second transfer position at the time when the first transfer is completed is greater than or equal to the predetermined distance. The second speed is reduced to a second speed at a predetermined timing, and if the distance is less than the predetermined distance, the intermediate transfer member 205 is rotated at the first speed without causing the second transfer even if the image leading end reaches the second transfer position. Then, at a predetermined timing thereafter, the speed is reduced to the second speed so as to perform secondary transfer.

In this way, even in all the cases of steps 1007 and 1008, the CPU 301 determines the timing of deceleration based on the sheet size stored in the memory 302, and during the time t_intvl from the first transfer completion timing, Since the carcass 205 is rotated to V1, the time required for detecting the HP 735 is shorter than in the conventional case of decelerating to V2 immediately after the first transfer completion timing, thereby shortening the cycle 707 and improving productivity. can do.

Next, with reference to Figs. 11 and 12, an example of &quot; single sheet attachment &quot; will be described.

Fig. 11 shows a timing chart of image formation of &quot; 1 sheet attachment &quot; and &quot; t_img &lt; t_itb &quot;, and Fig. 12 shows a timing chart of image formation of &quot; 1 sheet attachment &quot; and &quot; t_img &gt; t_itb &quot; to be.

In Figs. 11 and 12, t_itb and t_v have different settings from those in Figs.

In the case where it is judged that one sheet is attached in step 1002 of FIG. 8, the time t_1 from the detection of the HP of the intermediate transfer member 205 to the first transfer start of one image, and the first transfer from the first transfer start are determined. T_img = t_1 + t_pap + t_v is computed by making t_img the sum total of the time t_pap until transfer completion, and the time t_v required to decelerate a motor speed from V1 to V2 (step 1004).

Then, the intermediate transfer member 205 is compared with the time t_itb 'required for circumference including the transition from the speed V1 to the speed V2 (step 1006).

If t_img < t_itb ', that is, the time t_img is shorter than the time t_itb', the process proceeds to step 1007. If t_img &gt; t_itb ', that is, the time t_img is equal to or longer than the time t_itb', the process proceeds to step 1008.

In step 1007, if the motor speed is reduced to V2 immediately after completion of the first transfer, it is suitable for the HP 734. As shown in Fig. 11, the HP 734 is used as the reference signal for the second transfer start timing.

Then, t_intvl = t_itb '-t_img, the intermediate transfer member 205 is rotated to V1 for a time t_intvl that corresponds to the sheet size from the first transfer completion timing, and then the speed is reduced to V2. That is, the CPU 301 sets the timing of deceleration immediately before the start of the secondary transfer within the time from the end of the primary transfer to the start of the secondary transfer. In accordance with the detection of the HP 734, the CPU 301 starts the driving of the registration roller 269 to feed the recording sheet to the nip of the secondary transfer roller 204 and the intermediate transfer member 205. Then, the CPU 301 controls the bias voltage of the secondary transfer roller 206 so as to start secondary transfer at the timing at which the image leading end on the intermediate transfer member 205 passes the secondary transfer position. As a result, the time until the detection of the HP 734 is shortened, which results in shortening the cycle 707 and improving productivity.

On the other hand, in step 1008, even if the motor speed is reduced to V2 immediately after completion of the first transfer, it is not suitable until the detection of the HP 734. As shown in Fig. 12, the HP 735 is used as the reference signal for the second transfer start timing. In this case, the image tip on the intermediate transfer member 205 passes through the secondary transfer position from the completion of the primary transfer until the detection of the HP 735, but at this timing, the CPU ( 301 controls the bias voltage of the secondary transfer roller 206.

Then, t_intvl = t_itb + t_itb '-t_img. During the time t_intvl corresponding to the sheet size from the first transfer completion timing, the intermediate transfer member 205 is rotated to V1 and then decelerated to V2. In other words, the CPU 301 sets the timing of deceleration immediately before the start of the second transfer within the time from the end of the first transfer to the start of the second transfer. In accordance with the detection of the HP 735, the CPU 301 starts the driving of the registration roller 269, thereby feeding the recording sheet to the nip of the secondary transfer roller 204 and the intermediate transfer member 205. Then, the CPU 301 controls the bias voltage of the secondary transfer roller 206 so as to start secondary transfer at the timing where the image leading end on the intermediate transfer member 205 passes through the secondary transfer position. As a result, the time until the detection of the HP 735 is shortened, which results in shortening the cycle 707 and improving productivity.

That is, the CPU 301 performs the first transfer while rotating the intermediate transfer member 205 at the first speed, and if the distance between the image leading end and the second transfer position at the time when the first transfer is completed is more than the predetermined distance, the predetermined transfer is predetermined. Secondary transfer is performed by decelerating to the second speed at the timing, and if it is less than a predetermined distance, the secondary transfer is continued even when the image leading end reaches the secondary transfer position without rotating the intermediate transfer member 205 at the first speed. Then, at a predetermined timing thereafter, the speed is reduced to the second speed so that secondary transfer is performed.

In this way, in all the cases of steps 1007 and 1008, the CPU 301 determines the timing of deceleration based on the sheet size stored in the memory 302, and the intermediate transfer for the time t_intvl from the first transfer completion timing. Since the carcass 205 is rotated to V1, the time required for detecting the HP 735 is shortened, compared to the conventional method of decelerating to V2 immediately after the first transfer completion timing, which shortens the cycle 707 and improves productivity. We can plan.

As described above, the apparatus for outputting a good image by changing the rotational speed of the intermediate transfer member 205 during image formation and transferring the toner image onto the paper at a suitable toner transfer speed for various sheets after the first transfer is finished. When the speed of the intermediate transfer member 205 is decelerated to V2 before the second transfer, the timing for decelerating the intermediate transfer member 205 is made as slow as possible, and the time until HP detection at V2 is shortened. Can be suppressed.

In addition, t_itb 'shown in Figs. 8 to 12 may use t_itb instead of t_itb' when t_v is so small that the influence of the deceleration can be ignored or to simplify the calculation.

In this case, t_img and t_itb are compared in steps 1005 and 1006 of FIG. 8, t_intvl = t_itb-t_img in step 1007, and t_intv = 2 x t_itb-t_img in step 1008.

(Other Embodiments)

In the present embodiment, a system for decelerating the motor speed to V2 when the type of sheet is thick paper, an envelope, or OHP has been described. However, the relationship between the type of the sheet and the motor speed is not limited to the above. The system which prepared each motor speed corresponding to the kind of the branch sheet may be sufficient.

In addition, in this embodiment, although the system which decelerated to V2 after rotating a motor speed to V1 for predetermined time after completion | finish of primary transfer was demonstrated, it is not limited to V1 about motor speed, but rotates faster than V1. It may be a system that performs control to redetect the HP 271 of the intermediate transfer member 205 more quickly by rotating the motor to a speed of V2 after rotating the motor.

In this case, in determining t_intvl, the CPU 301 uses the time t_itb '' (not shown) for one week of the intermediate transfer body including transition of acceleration and transition of deceleration instead of t_itb 'of FIG. After completion of the first transfer, the intermediate transfer member 205 is accelerated by a predetermined time t_intvl and then decelerated.

As explained above, according to this embodiment, it becomes possible to provide the image forming apparatus which can aim at the improvement of productivity by shortening the time from completion of primary transfer to start of secondary transfer.

According to the present invention, it is possible to provide an image forming apparatus capable of improving the productivity by shortening the time from completion of the first transfer to the start of the second transfer.

Claims (11)

A photosensitive member carrying a toner image, A rotatable intermediate transfer member to which the toner image on the photosensitive member is transferred; Primary transfer means for primaryly transferring the toner image on the photosensitive member to the intermediate transfer member; Secondary transfer means for secondary transferring the toner image on the intermediate transfer member to a sheet; Having control means for controlling the intermediate transfer member and the secondary transfer means, When the control means is a predetermined sheet, the rotational speed of the intermediate transfer member after the first transfer is changed from the first speed to the second speed, Further, the control means determines, according to the image forming mode, whether to change the speed of the intermediate transfer member within one rotation in which the first transfer is performed or in one rotation following the one rotation in which the first transfer is performed. An image forming apparatus, characterized in that. The method of claim 1, wherein the predetermined sheet is any one of a thick paper, an envelope, a postcard, an OHP sheet, a label paper, a tab paper, and a second draft of an original drawing. An image forming apparatus. An image forming apparatus according to claim 1, wherein said image forming mode includes the number of toner images transferred on one circumference of said intermediate transfer member. An image forming apparatus according to claim 1, wherein said image forming mode includes a size of a toner image. The medium according to claim 1, wherein the control means determines whether the first distance between the leading end portion of the toner on the intermediate transfer member on the intermediate transfer member and the second transfer means is longer than a predetermined distance by the control means. And determining whether the speed of the transfer member is changed within one rotation in which the first transfer is performed or in one rotation following the first rotation in which the first transfer is performed. 6. The image forming apparatus according to claim 5, wherein the control means performs a speed change of the intermediate transfer member within one rotation in which the primary transfer is performed when the first distance is longer than the predetermined distance. 6. An image according to claim 5, wherein said control means performs the speed change of said intermediate transfer member within one rotation following the first rotation in which said primary transfer is performed when said first distance is equal to or less than said predetermined distance. Forming device. A fixing apparatus according to claim 1, further comprising fixing means for fixing the toner image on a sheet at a fixing speed after said second transfer, And said control means controls the speed of said intermediate transfer member substantially equal to said fixing speed. The image forming apparatus according to claim 1, wherein the first speed is higher than the second speed. 2. The intermediate transfer member according to claim 1, wherein the intermediate transfer member has a mark for detecting a leading end portion of the toner on the intermediate transfer member, And an detecting means for detecting a mark of the intermediate transfer member. The image forming apparatus according to claim 10, wherein the control means changes the speed of the intermediate transfer member immediately before the detection means detects a mark of the intermediate transfer member.

Images