JPH09311590A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To follow up the monocolor reproduction by returning a driving mechanism to a neutral position, whenever the formation of a toner image for one color is completed, and then, driving a stepping motor in an opposite direction, so as to switch the operation of supplying toner to plural developing units, at the time of executing the monocolor reproduction. SOLUTION: This image forming device is provided with an electrifier, a writing device 230, the plural developing units 14, the driving mechanism for switching an operation state for supplying the toner and a press-contact/unpress-contact mechanism for bringing a transfer roller 216 and a cleaning blade 22A into press-contact with a photoreceptor drum 10 and releasing the press-contact, on the periphery of the drum 10. Further, a single stepping motor for driving the driving mechanism and the press- contact/unpress-contact mechanism is provided. When a monocolor mode is detected, the driving mechanism is returned to the neutral position, after the formation of a preimage is completed and the stepping motor is driven in a fixed direction, to bring the transfer roller 216 and the cleaning blade 22A into press-contact with the photoreceptor drum 10 and release the press-contact. Then, the stepping motor is driven in the opposite direction, to switch the supplying operation to the plural developing units 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a drive mechanism for performing a pressure release of a transfer device / cleaning blade and a toner replenishing operation for replenishing toner with a single drive source.

[0002]

2. Description of the Related Art An image forming apparatus has been proposed in which a driving mechanism for releasing a pressure of a transfer device and a cleaning blade by a single driving source and a driving mechanism for selecting a color for replenishing toner are driven by separate driving sources. . The image forming apparatus having such a mechanism can be driven by simple control. However, cost reduction cannot be achieved because the number of parts increases. To reduce the cost of the image forming apparatus, reduce the total number of parts of the drive mechanism,
And it is necessary to operate various loads efficiently. The applicant of the present invention has proposed that the transfer device
A drive mechanism is proposed in which a single step motor drives the cleaning blade pressure release and toner replenishment operations. Such a drive mechanism selects the replenishment of yellow toner by rotating the motor in the reverse direction to rotate for 80 pulses from the neutral position in order to select a color for toner replenishment, and further rotates for 43 pulses. The replenishment of magenta toner is selected by, and the replenishment of cyan toner is selected by further rotating by 43 pulses, and the replenishment of black toner is selected by further rotating by 43 pulses. Therefore, when reproducing multi-color, there is no problem because they are performed in the order described above.

[0003]

However, if the above-mentioned drive mechanism tries to follow the reproduction of a mono color, the operation of returning to the neutral position after selecting the toner of a specific color is performed, and the neutral position is changed from the neutral position. The next selection color will be selected. This causes a problem that the operation timing of returning to the neutral position causes a phase shift from the operation timing of the transfer unit and the cleaning blade. Such a phase shift cannot quickly respond to a toner replenishment request. Problems occur in controlling the image forming process.

[0004] In view of the above technical problems, an object of the present invention is to provide
An object of the present invention is to provide an image forming apparatus provided with a drive mechanism that can follow the monochrome reproduction and transfer operation of the transfer device / cleaning blade and the toner replenishing operation by a single step motor.

[0005]

The above object can be achieved by the following constitutions.

(1) A driving mechanism, a transfer means, and a cleaning means for switching the operating states of a charging device, an image exposing means, a plurality of developing devices, and a toner replenishing means for replenishing toner to the plurality of developing devices around the periphery of the image carrier. An image forming apparatus provided with a pressure release mechanism for releasing pressure from the image carrier and a single step motor for driving the drive mechanism and the pressure release mechanism, and color mode detection means for detecting a color mode. If the color mode detection means detects a mono color mode, the driving mechanism is returned to the neutral position after the completion of the previous image formation, and the stepping motor is driven in one direction to cause the transfer means and the cleaning means to operate as described above. Switching the replenishment operation to multiple developing units by releasing pressure from the image carrier and driving the step motor in the opposite direction. An image forming apparatus comprising a control unit for controlling the image forming apparatus.

With the above arrangement, not only in multi-color reproduction but also in mono-color reproduction, the driving mechanism is returned to the neutral position every time a toner image of one color is formed, and then the step motor is moved in the opposite direction. By driving, the supplying operation to a plurality of developing devices is switched, so that it is possible to follow mono color reproduction.

[0008]

1 is a sectional view showing a schematic structure of an image forming apparatus according to this embodiment, and FIG. 2 is a sectional view showing each cartridge according to this embodiment.

The image forming apparatus according to the present embodiment has a main body 2 in which a cartridge containing various process members is loaded.
00, a double-sided paper feeding device 400 and a recording paper feeding device 600 are optionally provided. Prior to describing each component configuration, an image forming process of the image forming apparatus according to the present embodiment will be described.

The CPU 510 (see FIG. 9) grounds the photoconductor drum 10 having the OPC photoconductor applied on the drum and drives and rotates the photoconductor drum 10 in the clockwise direction. The CPU 510 applies a uniform charge of VH to the peripheral surface of the photosensitive drum 10 by corona discharge using a grid maintained at VG potential and a corona discharge wire by the scorotron charger 12. Prior to the charging by the scorotron charger 12, in order to eliminate the history of the photoconductor up to the previous print, exposure is performed by the PCL 11 using a light emitting diode or the like to eliminate the charge on the peripheral surface of the photoconductor.

Writing device 2 after uniformly charging the photosensitive member
Image exposure is performed by 30 based on the image signal. The writing device 230 is a device in which an optical path is bent by a reflection mirror through a polygon mirror, a fθ lens, etc., which rotates using a laser diode (not shown) as a light emitting source, and scanning is performed.
A latent image is formed by rotation (sub-scanning) of the photosensitive drum 10. In the present embodiment, a character portion is exposed to form a reversal latent image such that the character portion has a lower potential VL.

At the periphery of the photosensitive drum 10, there are provided developing units 14 each containing a developer containing toner such as yellow (Y), magenta (M), cyan (C), black (K) and a carrier. First, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer consists of a carrier in which ferrite is used as a core and is coated with an insulating resin around it, and a toner whose main component is polyester and pigments according to the color and charge control agents, silica, titanium oxide, etc. are added. The agent is regulated by the layer forming means to have a layer thickness (developer) of 100 to 600 μm on the developing sleeve 141 and is conveyed to the developing area.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is set to 0.2 to 1.0 mm, which is larger than the layer thickness (developer), and the AC bias of VAC and the DC bias of VDC are superposed between them. Applied. V
Since DC, VH, and toner charge have the same polarity, VAC
The toner that has been triggered to separate from the carrier does not adhere to the VH portion having a higher potential than VDC,
The toner adheres to the VL portion having a lower potential than VDC and visualization (reversal development) is performed.

After the visualization of the first color is completed, the process proceeds to the image forming process of the second color, the uniform charging is performed again by the scorotron charger 12, and the latent image based on the image data of the second color is formed by the writing device 230. It At this time, the charge elimination by the PCL 11 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the sudden decrease in the potential around the image.

Again, a latent image similar to that of the first color is formed and developed on the portion of the photoconductor having the potential of VH all over the peripheral surface of the photoconductor drum 10 without the image of the first color. However, in the portion where the portion where the image of the first color is present is developed again, the latent image of VM ′ is formed by the light shielded by the toner attached to the first color and the electric charge of the toner itself.
Development is performed according to the potential difference between DC and VM '.

An image forming process similar to that for the second color is performed for the third and fourth colors, and four steps are performed on the peripheral surface of the photosensitive drum 10.
A visible color image is formed.

On the other hand, the paper feed roller 2 from the paper feed cassette 203
The recording paper conveyed through the sheet No. 02 is temporarily stopped, and is fed to the transfer area by the rotation operation of the registration roller 209 when the transfer timing is adjusted.

In the transfer area, a transfer roller 216 is pressed against the peripheral surface of the photosensitive drum 10 in synchronism with the transfer timing, and the supplied recording paper is nipped and a multicolor image is transferred at once. .

Then, the recording paper is discharged at almost the same time by the pointed electrodes 217 which are brought into pressure contact with each other, separated by the peripheral surface of the photosensitive drum 10 and conveyed to the fixing device 220, where the heat roller 221 and the pressure roller 222 are heated and heated. After the toner is welded by the pressure, it is ejected to the outside of the apparatus through the paper ejection roller 223.

On the other hand, the photosensitive drum 10 from which the recording paper is separated
Removes and cleans the residual toner by pressing the blade 22A of the cleaning device 22. The charge is removed by the PCL 11 and charged by the charger 12, and the next image forming process starts. The blade 22A moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 10.

The structure of each cartridge will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the drum mount 30 includes a photosensitive drum 10 and a PCL 1 arranged on the peripheral surface thereof.
1. The charger 12, the developing devices 14, and the cleaning device 22 are housed and integrated. As shown in FIG. 2, the components housed in the drum base 30 are the photosensitive drums 10.
It is divided into a drum cartridge 40 that incorporates others, a developing cartridge 50 that incorporates each developing device 14 that contains Y, M, and C developers, and a developing cartridge 50A that incorporates only the developing device 14A that also contains K developer. Be accommodated.

The drum cartridge 40 is the photosensitive drum 1.
In addition to 0, a PCL 11, a charger 12, and a cleaning device 22 are incorporated, and the openings 40A, 40B, and 40 corresponding to the areas of exposure, development, and transfer on the surface of the photoconductor are provided.
It covers all photoreceptor surfaces except C. In the drum cartridge 40, the bearing 41 of the photosensitive drum 10 is brought into contact with the vertical groove 30 </ b> A of the drum base 30, and the bottom part is brought into contact with a pair of position regulating pins P <b> 1 provided on both inner side surfaces of the drum base 30. In this way, after the rotation is prevented, the horizontal and vertical positions are regulated and each device to be accommodated is set to a predetermined image forming position.

The opening 40A, which is the exposure area of the drum cartridge 40, is provided with a sliding type shield plate 42 in a narrow slit hole having a width sufficient for the writing beam to pass therethrough, so that the surface of the photosensitive member cannot be touched. It has become.

On the other hand, the developing cartridges 50 and 50A
Are biased by the compression springs 52 in a state where the position regulating pins P2 of the respective developing devices projectingly engage with the elongated holes on both side surfaces. The developing cartridges 50 and 50A are pressed to the left by the pressing pin P3 or P4 provided on the side door 34 forming the right side surface of the drum base 30, and the abutting rollers (not shown) coaxial with the developing sleeves 141 are provided. The gap between the peripheral surface of each developing sleeve 141 and the peripheral surface of the photoconductor drum 10 is set by pressing the peripheral surface of the photoconductor drum 10 under pressure.

The drum base 30 is a pedestal 30 installed above.
A plurality of toner replenishing means 300 for replenishing toner to each developing unit are provided integrally on the upper surface of B.

Each toner replenishing means 300 comprises a toner hopper 310 connected to each developing device by a toner carrying pipe (not shown) and a loading section 330 for mounting the toner cartridge 320 in a horizontal position. The toner replenishing means 300 are arranged adjacent to each other on the same plane in the axial direction of the developing sleeve 141 of the developing device 14. The developing sleeve 141 has a power source (not shown) for applying a DC bias and an AC bias set for each color, and the DC bias and the AC bias can be turned on / off individually under the control of the CPU 510.

The connection portion between the toner transport pipe (not shown) and each developing device is released and connected in accordance with the withdrawal and insertion of each developing device. In other words, when the drum cradle 30 is pulled out for jam processing, replacement of the drum cartridge, or the like, the connecting portion between the toner conveying pipe and the developing device does not separate, and the connecting portion separates only when each developing device is taken out. Reductions have been made. Further drum stand 3
When taking out 0, the toner replenishing means 300
The fact that there is no need to separate the device simplifies the configuration of these devices and simplifies the handling operation.

Further, by disposing the toner cartridge 320 and the toner hopper 310 on the same plane, the height of the space occupied by the toner replenishing means 300 can be reduced and the apparatus can be made compact.

As shown in FIG. 1, the image forming apparatus is provided with a recording paper passage detection sensor 70 for detecting the recording paper between the transfer roller 216 and the cleaning device 22.

The transfer roller 216 has a power supply (not shown) to which a positive or negative transfer bias can be applied.
Switching is performed under the control of the PU 510. When the recording paper exists at the transfer portion, the polarity of the bias voltage to the transfer roller 216 is set to the opposite polarity to the polarity of the toner. The recording paper passes through the transfer roller, and the photosensitive drum 10
When the transfer roller 216 comes into direct contact with the transfer roller 216, the polarity of the bias voltage applied to the transfer roller 216 is set to be the same as the charge polarity of the toner. When the recording paper is not present at the transfer portion, the polarity of the bias voltage to the transfer roller 216 is set to be the same as the polarity of the toner. By determining the operation of the transfer roller in this manner, when performing continuous image formation, the transfer roller 216 can be quickly cleaned during a period between adjacent recording sheets. Such a control method is also effective when the size of the transfer material in the traveling direction is not known in advance, for example, for manual feeding.

As shown in FIG. 1, the main body 200 is provided with a manual paper feed mechanism 270. The manual paper feed mechanism 270 has an insertion hole 271 for inserting a recording sheet and a recording paper inserted in the insertion hole 271. A detection member for detecting the paper is provided. The leading end of the inserted recording paper hits the built-in paper feed roller 272 and stops. The recording paper is conveyed by the rotation of the paper feed roller 272, and is conveyed toward the registration rollers 209 via the conveyance path 273. The manual feed mechanism 270 is the main body 2
The shaft is fixed to the shaft at 00 and is slightly movable outward.
Further, a part of the outer member is supported by the shaft, and the insertion hole can be opened.

As shown in FIG. 1, a paper feed cassette 203 containing a plurality of recording papers is provided in the main body 200 in a detachable manner. A half-moon-shaped paper feed roller 202 for feeding recording paper is provided on the paper feed cassette 203, and the paper feed cassette 2
A push-up plate 204 for pressing the uppermost recording sheet against the separation claw 205 is provided in the inside of the sheet. The recording paper placed on the push-up plate 204 is constantly pushed upward by a spring (not shown), the leading end of the recording paper is locked by the separation claw 205, and the recording paper is fed by the operation of an electromagnetic clutch (not shown). Roller 202
Is driven, and the uppermost sheet of recording paper is separated by the separation claw 205 and fed. The fed recording sheet is driven and conveyed by the intermediate sheet feeding roller 206, and is guided to the registration roller 209. CPU downstream of the registration roller 209
A registration shutter 215 that opens and closes the registration unit according to the control signal is provided. The CPU operates the detection member 219, and when the detection member 219 detects the recording paper, the recording paper directly enters the registration roller 209 and is stopped by the registration shutter 215. Further, a sensor 189 for detecting the transparency of the recording paper surface is provided upstream of the registration roller 209 in the paper feeding. At that time, the leading end of the recording paper abuts on the upper part of the guide member 213 to a projection provided on a part of the transmission sensor 199 rotatably attached to a part of the main body 200, and along the image forming surface of the recording paper. After the transmission sensor 199 is arranged at a predetermined position, the transparency of the image forming surface formed on the recording paper is detected.

A detection member for detecting the recording paper is provided above the paper feed cassette 203. Intermediate paper feed roller 20
Reference numeral 6 denotes a sheet cassette 203 and a curved reversing guide member 212.
It is provided between and.

The recording paper guide member 210 is a registration roller 2
The recording paper having passed through the transfer roller 09 is guided toward the transfer roller 216 which can be pressed and separated from the photosensitive drum 10.

The fixing device 220 is a device for fixing an image transferred onto recording paper, and includes a fixing heating roller 221 and a pressure roller 222. The discharge roller 223 is connected to the fixing device 22.
The recording paper is discharged from 0, and the discharged recording paper is conveyed upward by the conveying roller 224. The recording paper conveyed upward by the conveyance rollers 224 is transferred to the main body 200 by paper discharge rollers 225 provided in a paper discharge passage formed in the main body 200.
The recording surface is discharged onto a discharge tray 210 provided on almost the entire upper surface with the recording surface facing downward. A paper ejection detection sensor 229 is provided in the paper ejection path of the fixing device 220.

The motor 99 drives a paper feed roller 202 and an intermediate paper feed roller 20 via a speed reduction mechanism (not shown).
The driving force is transmitted to 6 via the toothed pulley and the intermediate gear group. The paper feed roller 202 is intermittently driven by an electromagnetic clutch (not shown). On the other hand, the registration roller 209 and the intermediate sheet supply roller 206 are configured to be driven and rotated at all times.

Next, the pressure release of the transfer roller 216 and the cleaning blade 22A and the toner replenishment selection mechanism will be described with reference to FIGS.
This will be described with reference to FIG.

FIGS. 3 and 4 are views of the pressure release mechanism of the transfer roller and the cleaning blade, FIG. 5 is a sectional view showing the combined state of the developing device and the toner carrying pipe, and FIGS. 6 and 7 are toner replenishment. FIG. 8 is a time chart showing the operation timing of the drive mechanism shown in FIGS. 3 and 4, which shows the main part of the drive device.

The motor 79 rotates clockwise when the image is not formed, so that the gear G10 on the motor shaft also rotates the sun gear G13 clockwise through the gear G11 and the coaxial gear G12. As shown in FIG. 3, the planetary gear G14 on the rotatable support plate 26 is revolved clockwise to drive the gear G15, and if necessary, for example, an operation such as color selection of toner to be supplied to the developing device 14 is performed.

The motor 79 rotates counterclockwise with the start of image formation to rotate the planetary gear G14 as shown in FIG.
Revolves in the counterclockwise direction, and rotates the gear G20 connected to the pressing drive of the transfer roller 216 in the counterclockwise direction.

The gear G20 is a gear G21 integrally formed with the cam plate 30 via a gear G21 coaxially integrated with a gear G22.
To transmit the power rotating counterclockwise.

The cam plate 30 is integrally formed with a cylindrical cam C having two large and small radii of curvature R and r, and further has a notch 30A corresponding to the fixed photosensor S at a position divided into four equal parts on its outer peripheral edge. 30B, 30C and 30D and 30E.

A pressing member 40, which is bent in a U-shape and rotates around a shaft 40A as a fulcrum, presses the tip end 40B of the cam C by the urging force of a tension spring 41, and the pressing member 40 further presses the cam C. A pressure contact lever 50 that supports the transfer roller 216 is pressed against the pin 42 by the biasing force of the tension spring 51.

In the cam plate 30, as shown in FIG. 3, the angle at which the notch 30A is detected by the photosensor S is taken as the rotational neutral position (N · P), and at this angle, the cam C has a large radius of curvature R. The tip end portion 40B of the pressing member 40 is pressed against. Therefore, the pressing member 40 occupies the position rotated counterclockwise, and the pressing pin 42 presses the protrusion 42 of the pressing lever 50 to move the pressing lever 50 to the shaft 5.
It is placed at a position rotated clockwise with 0A as a fulcrum, whereby the transfer roller 216 is retracted to a position separated from the peripheral surface of the photosensitive drum 10 in the neutral position (N · P).

When the cam C is rotated by the counterclockwise rotation of the motor 79 to bring the tip portion 40B of the pressing member 40 into pressure contact with a portion having a small radius of curvature r as shown in FIG. Occupies a position rotated in the direction, and the pressing pin 42 is separated from the protrusion 52 of the pressing lever 50 to free the pressing lever 50, whereby the transfer roller 21.
6 is pressed against the peripheral surface of the photosensitive drum 10 by the urging force of the tension spring 51 to start the image transfer operation.

The rotation speed of the motor 79 is controlled by a detection signal generated by the photosensor S sequentially detecting each notch of the cam plate 30 as shown in FIG. 8, and the pressure contact state of the transfer roller 216 is maintained. Three notches 30D and 30
After E is continuously detected, the transfer roller 216 is released from the pressure contact, stopped again at the position where the notch 30A is detected, and the cam C is again set to the initial position shown in FIG. 4, that is, the neutral position described above.

The rotation of the gear G25 (see FIG. 6) is transmitted to the gear G26 arranged in the right angle direction through the deflection gear pair 80, and further, as a sun gear 4 via a plurality of intermediate gears G27.
It is transmitted to the individual gears G28 and G28A. Each of the gears G28 and G28A is a support lever 64 that freely rotates about its rotation center as a fulcrum restricting means of the planetary gear.
And a gear G29, which is a planetary gear that meshes with the gears G28 and G28A, at the other end.

The gear G35 is a cam mechanism shown in FIGS.
As shown in FIG. 7, four cam members 70Y, 70M, 70C and 70K for sequentially changing the phase of the cutout portion by, for example, one-fifth circumference are provided on the coaxial shaft 70 as shown in FIG. The motor 89 rotates a predetermined number of times according to the color of the toner, and each cam member rotates one fifth. As a result, for example, when a toner replenishment signal is input to the developing device 14 containing the magenta developer, the cam member 70M is rotated by the driving of the motor and the cutout portion faces the protrusion 65 of the support lever 64. As a result, the gear G29 revolves around the gear G28, and the gear G4 included in the magenta toner transport screw 121 that is a driven gear.
The transfer of the toner to the developing device 14 is started by meshing with 0M. On the other hand, cam members 70Y and 70C other than the cam member 70M
And 70K have support levers 64 with respective notches.
Since the gears G29 are not faced to the protrusions 65 of the toner conveying screw 121,
Since none of the Y, 40C, and 40K meshes with each other, toner is not supplied to the yellow, cyan, and black developing units 14. Thus, the cam members 70Y, 70M,
By sequentially switching the phases of the notch portions of 70C and 70K, the replenishment of toner to each developing device 14 is alternately performed.

As described above, since the power for toner replenishment is reliably transmitted by the meshing of gears, it is possible to obtain a stable toner replenishment function as compared with the transmission method using the clutch mechanism.

The above is the schematic mechanism of the image forming apparatus according to the present embodiment.

Next, a schematic structure of the engine controller used in the image forming apparatus according to the present embodiment will be described with reference to FIG.

FIG. 9 is a block diagram showing the main structure of the engine controller in this embodiment.

The engine controller 500 receives page data and print parameters from an external device such as a personal computer, and the writing device 230 described above is used.
The drive timing of the scorotron charger 12, the developing device 14, the transfer roller 216, and the cleaning device 22 is controlled, and the recording paper is fed from the paper feeding device 400, the paper feeding cassette 203, or the manual paper feeding mechanism 270. It controls timing, and includes CPU 510, SRAM 520, and ROM.
530, a developing device drive system 540, a transfer cleaning drive system 550, a paper feed drive system 560 and the like. The configuration of each part will be described below.

The CPU 510 executes a sequence program for executing the electrophotographic process from the SRAM 520 by using a reference signal for one round of the drum which is an external signal as a trigger, and the motor drivers 542, 552, 5
62 and the solenoid 174 are controlled to drive the recording paper based on detection signals from the passage detection sensors 70, 189, 219 and 229, and purge processing corresponding to recovery processing from a jammed state is performed. Run.
The CPU 510 has a function of detecting a color mode input from an operation unit (not shown).

Further, the CPU 510 has a function of detecting the size of the recording paper by an input from an operation unit (not shown).

The ROM 530 stores the warm-up process, the multi-color print process, the mono-color print process, the letter size print sequence, the postcard size print sequence, the first purge process and the second purge process as described above. A program corresponding to a sheet feeding process including a process, a manual sheet feeding process, and a double try sequence is written.

The SRAM 520 stores parameters necessary for executing various print sequences.

The developing device drive system 540 selects a driving state of a driving mechanism of a developing device (not shown), and includes a gate array 541, a motor driver 542, and a solenoid 174.
And a control line for controlling the driving state of. The gate array 541 uses the timing signal from the CPU 510 to drive the motor 7
The forward / reverse rotation signal for instructing the rotation direction of 9 and the on / off signal for designating either rotation or stop are sent to the motor driver 542. Further, the CPU 510 sends the internal clock CLOCK to the motor driver 542. The motor driver 542 sends a pulse signal for giving a predetermined rotation speed to the motor 79. As a result, the motor 79 rotates forward or backward at a predetermined speed. By turning on / off the solenoid 174 in response to a control signal from the CPU 510, the tip of any one of the above-mentioned regulating members comes into contact with the supporting member.

The transfer cleaning drive system 550 is for instructing selection of the blade / transfer roller 216 pressure-bonded / released from the photosensitive drum 10 and toner replenishment in the above-described various sequences, and the gate array 551 and the motor driver. And 552. The transfer cleaning drive system 550 can change the speed and timing of the pressure contact / release operation between the blade and the transfer roller 216 during continuous printing and during other printing.
The gate array 561 sends a SAVE signal and an ENABLE signal for controlling the driving state of the motor driver 552 to the motor driver 552 according to the print size and print sequence. In addition, the CPU 510 uses two clocks CLOCKA and CLOCK from the internal clock.
B is supplied to the motor driver 552. Therefore, the motor driver 552 rotates the motor 59 at a speed according to various sequences. This makes transfer /
The cleaning drive mechanism will perform the pressure release operation of the transfer roller 216 and the blade at a predetermined speed.

The paper feed drive system 560 controls the conveyance speed of the recording paper according to the print size, print mode, etc., and includes a gate array 561 and a motor driver 562.
Consists of The gate array 561 is shared with the transfer cleaning drive system described above, and the SAVE signal and the ENABLE signal for controlling the drive state of the motor driver 562 according to the control signal from the CPU 510 and the clock signals CLOCKA, CLOCK for giving the drive timing.
B is sent to the motor driver 562. Therefore, the motor driver 562 rotates the motor 99 at a speed according to various sequences. As a result, the recording paper is fed at a speed according to various sequences.

The above is the schematic configuration of the engine controller in the present embodiment.

FIG. 10 is a flowchart showing the print sequence.

Upon receiving the print start request command, the CPU 510 drives the print start task (step 901). As a result, the polygon mirror starts rotating, and the rotation of the main motor causes the photosensitive drum 1 to rotate.
0 is rotated.

The CPU 510 activates the sequence start task (step 902). Thereby, various modes input from the operation unit (not shown) are set. For example, a mono color mode, a multi color mode, or the like.

When the CPU 510 receives the reference interrupt signal generated after one rotation of the photosensitive drum 10, it starts the image start task (step 903). As a result, the developing sleeve 141 is rotated and a developing bias is applied. The reference interrupt signal is obtained from an encoder (not shown) that detects the phase of the photosensitive drum 10.

Following this, the photosensitive drum 10 is driven and rotated clockwise. PCL11 consisting of light emitting diode
Prior to the charging by the scorotron charger 12, the peripheral surface of the photoconductor is neutralized by performing exposure to eliminate the history of the photoconductor until the previous printing. The scorotron charger 12 applies uniform charging of V _{H to} the peripheral surface of the photoconductor drum 10 by corona discharge by a grid held at V _G and a corona discharge wire. The writing device 230 scans with the optical path bent by a reflection mirror via a polygon mirror, an fθ lens, and the like, which rotate using a laser diode (not shown) as a light emitting light source. In the present embodiment, a character portion is exposed to form a reversal latent image such that the character portion has a lower potential _VL . First, development of the first color is performed by a developing sleeve 141 which rotates while holding a developer with a built-in magnet. The developer is a developing sleeve 1 by the layer forming means.
The layer 41 is regulated to have a layer thickness (developer) of 100 to 600 μm and is conveyed to the developing area. The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is the layer thickness (developer).
As 0.2~1.0mm greater than, V _AC during this time
AC bias of _DC and DC bias of V _DC are superimposed and applied. Since V _DC and V _H and the toner charge have the same polarity,
The toner that has been given the opportunity to be separated from the carrier by V _AC does not adhere to the V _H portion having a higher potential than V _DC ,
It adheres to the V _L portion having a lower potential than V _DC and is visualized (reversal development).

When the CPU 510 receives the reference interrupt signal after the visualization of the first color is completed, it enters the image forming process for the second color, and the scorotron charger 12 performs uniform charging again, and the image data for the second color is used. A latent image is formed by the writing device 230. At this time, the charge elimination by the PCL 11 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the sudden decrease in the potential around the image. Of the photoconductors whose potential is V _H over the entire surface of the photoconductor drum 10 again, 1
A latent image similar to that of the first color is formed and developed on the portion without the image of the first color, but at the portion where the image with the first color of the image is developed again, the light is blocked by the toner attached to the first color. A latent image of V _M ′ is formed by the charges of the toner itself and the toner, and development is performed according to the potential difference between V _DC and V _M ′. In the overlapping portion of the first color image and the second color image, if the development of the first color is performed by forming a _VL latent image, the balance between the first color and the second color is lost. There may be an intermediate potential where _H > V _M > V _L.

The CPU 510 performs the image forming process for the third and fourth colors by receiving the interrupt reference signal as in the case of the second color, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10. .

On the other hand, from the paper feeding cassette 203 to the paper feeding roller 2
02 is temporarily stopped, and is fed to the transfer area by the rotation of the feed roller 209 when the transfer timing is adjusted. In the transfer area, a transfer roller 216 is pressed against the peripheral surface of the photosensitive drum 10 in synchronization with the transfer timing, and the fed recording paper is sandwiched to transfer the multicolor image at once. Next, the recording paper is neutralized by a pointed electrode 217 provided with a slight gap, separated by the peripheral surface of the photoconductor drum 10 and conveyed to the fixing device 220, and the toner is heated and pressed by the heat roller 221 and the pressure roller 222. After being welded, the sheet is discharged to the outside of the apparatus via the sheet discharge roller 223. The transfer roller 216 is retracted and separated from the peripheral surface of the photosensitive drum 10 after passing the recording paper to prepare for the formation of the next toner image. On the other hand, the photosensitive drum 10 from which the recording paper has been separated removes and cleans the residual toner by the pressure contact of the blade 22A of the cleaning device 22, and the P
Upon receiving the charge removal by CL11 and the charging by the charger 240, the next image forming process is started. The blade 22A moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 10.

When the image forming operation described above is completed, the CPU 510 activates the image end task (step 9).
04). As a result, the rotation of the developing sleeve 141 is stopped, and the application of the developing bias to these developing sleeves 141 is stopped.

The CPU 510 activates the check task (step 905). As a result, the CPU 510
It is determined whether or not there is a start command for instructing the start of the next print operation from the print controller (step 9).
06), if it is determined that there is no next print, the print end task is activated (step 907). As a result, the CPU 510 causes the polygon mirror and the photosensitive drum 10 to
Stop rotating. As a result, this print sequence task is completed. The CPU 510 is
When the start command is received in the check task of step 905, the above-mentioned tax from step 902 to step 905 is sequentially activated.

The CPU 510 activates the standby task at the same time when the print sequence task ends (step 910). As a result, the CPU 510 causes the fan to rotate at a low speed and lowers the fixing temperature.

The above is the print sequence of the color printer according to the present embodiment.

A cam task corresponding to each print mode will be described with reference to FIGS. 11 to 13.

FIG. 11 is a flow chart showing the control operation of the interrupt handler for stopping the crimping motor.

When the CPU 510 activates the crimp motor stop interrupt handler, the stack pointer is saved (step 301), new interrupts are prohibited (step 302), and the pulse counter is incremented (step 303).

The CPU 510 compares the count value of the pulse counter with the set pulse number (step 304). CP
If the U510 determines in step 304 that the count value is larger than the set pulse number, it stops the rotation of the motor 59 (step 305) and clears the set pulse data and the pulse counter (step 306). CPU510
Permits the next interrupt (step 307), restores the contents of the stack pointer from the save destination, and ends this routine (step 308).

FIG. 12 is a flow chart showing a reversing module for reversing the motor 79.

When the reverse rotation module is activated, the CPU 510 stops the timer (step 401) and returns the phase of the cam 30 described with reference to FIGS. 3 and 4 to the neutral position (step 402).

The CPU 510 sets the motor 79 to 300PP.
Data for rotating in the opposite direction at S is set in registers A and B (step 403). The CPU 510 sets the interrupt contents of compare match (step 40).
4). The CPU 510 reads the set pulse number (step 405) and initializes the counter (step 40).
6). As a result, the CPU 510 brings the motor 79 into a rotatable state (step 407).

FIG. 13 is a flowchart showing the cam task.

Such a cam task judges whether the postcard mode is the normal size mode and whether it is multi-color or mono-color, and determines the pressure release speed of the transfer roller 216 and the blade depending on the respective recording paper modes. And a toner replenishment selection operation.

The CPU 510 sets the motor 79 to 50 in accordance with the recording paper size mode input from the operation unit (not shown).
Whether the motor is rotated at 0 PPS to detect the neutral position (step 601), the motor 79 is rotated at 300 PPS to detect the neutral position (step 602), or the crimping motor is rotated at 500 PPS to turn on the blade (step). 603) or the motor 79 is rotated at 300 PPS (step 62).
Judgment 1).

If the determination at step 601 is affirmative, the CPU 510 rotates the motor 79 at 500 PPS (step 604), waits for 100 msec (step 605), and executes the neutral position detection process (step 606). .

If the CPU 510 makes a negative determination in step 601 and makes a positive determination in step 602, it rotates the motor 79 at 300 PPS (step 6
07), wait 20 msec (step 608), and perform neutral position detection processing (step 60).
6).

If the CPU 510 makes a negative determination in steps 601 and 602, and makes a positive determination in step 603, it rotates the motor 79 at 500 PPS (step 609) and waits 1.5 seconds (step 61).
0), edge detection processing is performed (step 61).
1).

If the CPU 510 makes a negative determination in steps 601 to 603 and makes a positive determination in step 621, it rotates the motor 79 at 300 PPS (step 622) and waits for 20 msec (step 62).
3), edge detection processing is performed (step 62).
4).

If the CPU 510 makes a negative determination in steps 601 to 603 and step 621, it rotates the motor 79 at 500 PPS (step 62
5), wait 20 msec (step 623), and execute edge detection processing (step 624).

By activating the above-mentioned cam task, the image forming apparatus according to the present embodiment can release the pressure from the transfer roller 216 and the blade at a speed corresponding to the recording paper size mode, and can also perform the toner replenishing operation. Since it is possible to follow the transfer roller 216, the transfer roller 216 can be used, for example, when printing a small size such as a postcard.
Since the pressure release operation of the blade and the blade can be performed at high speed at 500 PPS, it is possible to prevent the transfer roller 216 from being soiled and the back surface of the recording paper to be soiled due to the delay of the pressure release operation of the transfer roller 216. In the normal recording size mode such as B size, the pressure release operation of the transfer roller 216 and the blade is performed three times during the printing operation.
Since 00PPS can be performed at a low speed, it is possible to appropriately reproduce an image without causing a writing deviation due to the vibration of the photosensitive drum 10.

[0091]

As described above, the image forming apparatus of the present invention is provided with the above-mentioned configuration, and the drive mechanism is returned to the neutral position each time the formation of a toner image of one color is completed not only in multi-color reproduction but also in mono-color reproduction. After that, by driving the step motor in the opposite direction, the replenishment operation to the plurality of developing devices is switched, so that it is possible to follow mono color reproduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a cross-sectional view showing each cartridge according to the embodiment.

FIG. 3 is a view showing a pressure release mechanism of a transfer roller and a cleaning blade.

FIG. 4 is a view showing a pressure release mechanism of a transfer roller and a cleaning blade.

FIG. 5 is a cross-sectional view showing a combined state of a developing device and a toner transport pipe.

FIG. 6 shows a main part of a toner replenishing drive device.

FIG. 7 shows a main part of a toner replenishing drive device.

FIG. 8 is a time chart showing the operation timing of the drive mechanism shown in FIGS. 3 and 4.

FIG. 9 is a block diagram showing a main configuration of an engine controller according to the present embodiment.

FIG. 10 is a flowchart illustrating a print sequence.

FIG. 11 is a flowchart showing a control operation of an interrupt handler for stopping the crimp motor.

FIG. 12 is a flowchart showing a reversing module for reversing a motor.

FIG. 13 is a flowchart showing a cam task.

[Explanation of symbols]

30 cam plate 50 pressure contact lever 79 motor 171 and 172 support member 173 regulating member 174 solenoid 175 casing 510 CPU 520 SRAM 530 ROM 541,551,561 gate array 542,552,562 motor driver G11 to G15, G20 to G23, G30 to G35 gear

Claims (1)

[Claims] 1. A drive mechanism, a transfer means, and a cleaning means for switching the operating states of a charging device, an image exposing means, a plurality of developing devices, and a toner replenishing means for replenishing toner to the plurality of developing devices on the periphery of an image carrier. In an image forming apparatus provided with a pressure release mechanism for releasing pressure from the image carrier and a single step motor driving the drive mechanism and pressure release mechanism, a color mode detection unit for detecting a color mode, and a color When the monochromatic mode is detected by the mode detection means, the drive mechanism is returned to the neutral position after the completion of the previous image formation, and the step motor is driven in one direction to move the transfer means and the cleaning means to the image carrier. The pressure is released from the press and the step motor is driven in the opposite direction to switch the replenishment operation to multiple developing devices. An image forming apparatus comprising a control means.