JPH04143773A - Image formation device - Google Patents

Abstract

PURPOSE:To form optimum images at all times by detecting the environmental state of a transfer means at specific timing and setting and controlling a desired transfer bias at least once. CONSTITUTION:When environmental information on the transfer means 10a is detected at specific timing after the start of a printing sequence, a transfer bias setting means 26a sets the desired transfer bias in the transfer means 10a >=1 time to set the best desired transfer bias for the environmental state of the transfer means 10a at all times. Namely, once code information is inputted to a microprocessor 17, a prefeed instruction is sent out to bring the transfer roller 10a of a photosensitive drum 2 under constant-current control and a voltage which is generated at this time is held and applied at the time of printing. For example, when the transfer roller 10a is brought under the constant- current control, a voltage which is about 2.5 KV in normal environment, about 3.0 KV in low-temperature, low-humidity environment, or about 2.0 KV in high- temperature, high-humidity environment is generated to obtain an excellent transfer image in corresponding environment. Consequently, even if the environment changes, the best developed image which has no transfer defect can be transferred.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus that converts character or graphic information into bitmap information and forms an image on a recording medium based on the converted bitmap information. .

[Prior art] Electronic printers are capable of high-resolution, high-quality printing;
In recent years, a large number of printers such as laser beam printers, LED printers, and liquid crystal printers have been developed and widely used. Taking advantage of its high-quality features, it is being used to output complex figures and graphics.

A controller (for example, a Bost Script Controller) that processes complex image data covering one page of a printed surface requires at least one page worth of image memory (page memory). For example, printing A4 size paper with a resolution of 300 DPI (dots per inch) requires a page memory of 1 MB.

The amount of image information processed in such high-quality printers is quite large. For this reason, the image data handled on the memory device of a computer or other information processing equipment system is not raw rask image data (it is often coded or programmed data).

The performance of a page printer is determined by how quickly one page's worth of coded image information is converted into one page's worth of rask image information and printed.

A conventional example of the control form of this page printer will be explained with reference to FIGS. 9 and 10.

FIG. 9 is a sectional view showing an example of the configuration of a conventional image forming apparatus, and shows a laser beam printer as a page printer.

In the figure, 1 indicates the main body of the laser beam printer.

Reference numeral 2 denotes a photosensitive drum, and the surface of the photosensitive drum 2 is horizontally scanned by a laser beam emitted from a laser scanning device 3 via a mirror 4 .

A primary charging roller 5 charges the surface of the photosensitive drum 2 uniformly. A developing device 6 performs, for example, jumping development on a developer (toner) 8 using a developing roller 7 to visualize the electrostatic latent image on the photosensitive drum 2. A cleaner 9 collects toner remaining on the photosensitive drum 2. A transfer charger 10 transfers a toner image onto a transfer material 13 housed in a paper cassette 14.

Reference numeral 11 denotes a registration roller, in order to synchronize the leading edge of the image on the sheet of paper picked up by the sheet feeding roller 12 with the leading edge of the image on the photosensitive drum 2.
3 is stopped, and the transfer material 13 is re-fed at a predetermined timing.

15 is a fixing roller, and the toner 8 transferred to the transfer material 13 is
Apply pressure to fix it. A discharge roller 16 discharges the transfer material 13 on which the image forming process has been completed to the outside of the machine.

FIG. 10 is a block diagram showing a control configuration of the image forming apparatus shown in FIG. 9, and 25 represents an external information processing device (for example, a personal computer or a workstation) other than the laser printer. 27 is an external interface (for example, a parallel interface (manufactured by Centronics) or R3232C), which sends coded image information (for example, ASCII code, hereinafter referred to as code information) to the laser beam printer. Within the laser beam printer, the code information is received at an interface circuit 18. Microprocessor 17 receives the code information received by interface circuit 18 via internal bus 28. This internal bus 28 is composed of a data bus, an address bus, a control bus, etc.

Further, the microprocessor 17 operates according to a control program stored in the memory 21.

Note that the memory 21 is composed of a nonvolatile ROM.

The microprocessor 17 somewhat processes the code information obtained from the interface circuit 18 and stores it in the memory 19. The memory 19 is a RAM for storing code information. The microprocessor 17 sequentially stores the code information received from the outside in the RAM 19, and also converts the code information into image information of a dot image and stores it in the RAM 20. The RAM 20 is a memory for storing image data (bitmap memory). 22 is a DMA controller that reads data stored in the RAM 20 and sends it to the rask conversion circuit 24.

DMA controller 22 can exclusively occupy internal bus 28 independently of microprocessor 17 . When the microprocessor 17 detects that the image data stored in the RAM 20 has reached one page (that is, when it detects that all the code data for one page has been converted into image data), it sets the DMA controller 22 in the active state. Make it.

The DMA controller 22 and the microprocessor 17 alternately occupy the internal bus 28.

The DMA controller 22 then uses the rask conversion circuit 24.
In response to the request, image data is sequentially read from the RAM 20 and sent to the rask conversion circuit 24.

In the rask conversion circuit 24, the DMA controller 2
The parallel image data received from 2 is converted into serial image data. Then, serial image data is outputted to a laser driver (not shown) of the mechanical control section 26 in synchronization with the horizontal synchronization signal to modulate the laser beam.

The microprocessor 17 not only develops the code data into image data, but also instructs the mechanical control section 26 of the laser printer for various printing processes. I1
The 0 driver 23 is in charge of an interface between the microprocessor 17 and the mechanical control section 26.

Next, mechanical control of the laser beam printer will be described in more detail with reference to FIG.

When the microprocessor 17 finishes developing one page of code data and storing the image data in the memory 20, it rotates a transport motor (not shown) via the I10 driver 23. At this time, photosensitive drum 2. -Next charging roller5. Developing roller 7°Fixing roller 15. The discharge roller 16 and the like start rotating. Rotation control of the transport motor is performed by a mechanical control section 26.

The laser scanning device 3 includes a laser scanning mirror therein,
Laser scanning motor, laser emitting device.

It is equipped with a laser drive circuit, etc. I10 driver 2
3 rotates the conveyance motor and also rotates the laser scanning motor inside the laser scanning device 3. And engineering/
○The driver 23 is the primary charging roller 5. A high voltage is sequentially applied to the developing roller 7 and the transfer charger 10. Also, ■／○
The driver 23 turns on the clutch attached to the paper feed roller 12, and transfers the transfer material 1 loaded in the paper cassette 14.
3 is fed. The fed transfer material 13 is temporarily stopped by the registration rollers 11. Then, the mechanical control section 26
is the transfer material 13 fed to the I10 driver 23.
It is notified that the registration roller 11 has been reached. When the transfer material 13 stops on the registration rollers 11, the microprocessor 17 activates the DMA controller 22. Then, serial image data is sent out from the rask conversion circuit 24. The sent serial image data is input manually to the laser scanning device 3, and the photosensitive drum 2 is irradiated with a laser beam modulated by the image data. Then, a latent image is formed on the surface of the photosensitive drum 2,
The toner image is visualized by the developing device 6.

The transfer material 13 stopped by the registration rollers 11 is conveyed again by the registration rollers 11, and the toner image is transferred onto the transfer material 13 by the transfer charger 10. The transfer material 13 to which the toner 8 has adhered is thermally fixed by a fixing roller 15, and then discharged from the machine by a discharge roller 16. The toner 8 that has not been transferred to the transfer material 13 by the transfer charger 1o is collected by a cleaner 9. The code information given from the external information processing device 25 as described above is printed on the sheet as image information.

When printing the rotation data, printing is performed at the timing shown in the timing chart shown in FIG.

That is, at timing (a), microprocessor 1
7 starts receiving code information. At the same time, the microprocessor 17 starts image development and stores the image data in the memory 2o. When the reception of the first page code data is finished at timing (b), reception of the second page code information is subsequently started at timing (C). If the image development of the first page is completed at timing (d), the conveyance motor is rotated at timing (f) to perform a paper feeding operation. Then, at timing (g), the registration roller 11 is driven, and at timing (h), the DMA controller 22 starts reading image data, and at timing (h), serial image data is formed by the rask conversion circuit 24, and the laser Exposure begins. Then, the laser exposure of the first page ends at timing (i). Further, reception of the code information for the second page is completed at timing (e), and image development for the second page starts at timing (i). Thereafter, the printing operation for the second page is performed in the same sequence as for the first page.

In Figure 11, the timing (a) ~ when image development is performed
(d) and timings (i) to (j) (this is also the period of laser exposure) and image data readout timings (i) to (j) are completely independent, and there is no overlapping period. This has image memory for one page.

In such a method, the period (f) to timing (h) (
Alternatively, during the period from timing (k) to timing (m)), no access is made to the memory 2o. Therefore, in a laser beam printer in which the distance from the paper feed roller 12 to the registration roller 11 is very long, the throughput (the number of sheets printed per unit time) decreases. If the image memory is provided for two pages, the image development period and the image data readout period can overlap, and throughput can be improved. However, in that case, the memory cost will double.

In order to solve these drawbacks, the applicant proposed a recording device disclosed in Japanese Patent Application No. 1-195626.

In this proposal, when the microprocessor 17 receives one page of code information from an external information processing device 25 such as a host computer, the feeding operation of the transfer material 13 such as paper is started, and the transfer material 13 is transferred at a predetermined position. The conveyance of the material 13 is stopped and kept on standby. Thereafter, when the microprocessor 17 has finished developing the code information into dot image image data, the dot image image data is sequentially sent as serial image data to the mechanical control section 26, which modulates the laser beam. The electrophotographic photosensitive drum 2 is exposed to light, and the transfer material 13 is restarted from a standby state in synchronization with the exposed image.

[Problems to be Solved by the Invention] However, in the proposal shown in the recording apparatus disclosed in the above-mentioned Japanese Patent Application No. 1-195626, as shown in FIG. The transfer material 13 is on standby in a state forming a loop or in a state in which it is held between the registration rollers 11 as shown in FIG.

In this way, in FIG. 12, the transfer material 13 is
In FIG. 13, the transfer material 13 is subjected to a deforming force due to the nip of the registration rollers 11.

In addition to plain paper, the transfer material 13 can be a second original paper, an OHP film, artificial paper, an envelope, etc. However, since it is a thin sheet, if the transfer material 13 is left for a long time in the above-mentioned state, the transfer material 13 will cause local deflection.

In this way, when the bent portion comes into contact with the photosensitive drum and transfers the toner image, adhesion deteriorates, resulting in poor transfer. This may be caused by the fact that the toner is not transferred in some areas, resulting in the transferred image becoming white, or the toner image being transferred with insufficient contact, resulting in a blurred transferred image.

For this reason, proposals have already been made to improve the above-mentioned situation by using contact transfer means such as roller transfer or belt transfer instead of non-contact transfer means such as a corona charger.

The improvement process using the transfer roller will be described below.

The transfer roller is always in contact with the photoconductor drum, and when the transfer material reaches the transfer section, it is pressed against the photoconductor under constant pressure, ensuring high adhesion even if the transfer material is warped or cracked. Thus, the above-mentioned transfer omissions, blurring, etc. can be prevented.

[Problem to be Solved by the Invention J] However, since the transfer roller is always in contact with the photoreceptor surface or the transfer material, it has the problem that it is much more susceptible to changes in load impedance than non-contact corona chargers etc. was there.

Specifically, environmental fluctuations in the roller material and transfer material are major factors. In particular, the roller material has large resistance fluctuations and exhibits stable characteristics under various environments, making it extremely difficult to obtain good transferability.

Therefore, there is a need for a mode that measures the resistance of the transfer roller by some means, and detects the resistance fluctuation of the transfer roller.
It is desirable to set the optimum transfer bias for each environment.

However, when such a resistance measurement mode is applied to a prefeed system, there are serious problems such as the drum drive time during printing operation becomes longer and it becomes impossible to improve the throughput, which is a characteristic of the prefeed system. .

The present invention has been made to solve the above-mentioned problems, and is provided in an image forming apparatus equipped with a transfer means that contacts an image carrier and transfers a developer onto a transfer paper. By detecting the environmental condition and controlling the setting of a desired transfer bias for the transfer means at least once, the optimum transfer bias is set for the transfer means,
An object of the present invention is to obtain an image forming apparatus capable of constantly forming optimal images without reducing throughput.

[Means for Solving the Problems] The image forming apparatus according to the present invention applies a desired transfer bias to the transfer means at least once or more based on environmental information of the transfer means detected at a predetermined timing after the start of a print sequence. A transfer bias setting means is provided for setting the transfer bias.

Further, the transfer bias setting means is configured to set a desired transfer bias based on environmental information of the transfer means detected during a predetermined pre-rotation process at the start of continuous printing.

Further, the transfer bias setting means is configured to reset a desired transfer bias based on the elapsed time of pixel conversion by the pixel conversion means.

Further, the transfer bias setting means is configured to set a desired transfer bias when a pre-feed sheet feeding request is made to the sheet feeding means.

[Function] In the present invention, when the environmental information of the transfer means is detected at a predetermined timing after the start of the print sequence, the transfer bias setting means sets the desired transfer bias on the transfer means one or more times and always transfers. It is possible to set a desired transfer bias that is optimal for the environmental conditions of the means.

Further, the transfer bias setting means sets a desired transfer bias based on environmental information of the transfer means detected during a predetermined pre-rotation process at the start of continuous printing, and sets a desired transfer bias for subsequent continuous printing at the start of continuous printing. It is possible to set the optimum desired transfer bias.

Further, the transfer bias setting means resets the desired transfer bias based on the elapsed time of pixel conversion by the pixel conversion means, and sets the desired transfer bias so as to obtain the optimum image even if the pixel conversion elapsed time is long. Allows to set bias.

Further, the transfer bias setting means makes it possible to set a desired transfer bias at the time of a pre-feed paper request to the paper feed means, and complete setting of the transfer bias before starting a predetermined pre-rotation process.

[First Embodiment 1] FIG. 1 is a sectional view illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention, and shows, for example, a laser beam printer. The configuration and operation will be explained below.

A corona charger 5 is used to uniformly charge the surface of a negatively charged OPC drum (photosensitive drum) 2. Next, the laser scanner 3 exposes the image to form a latent image. Next, the toner 8 in the developing device 6 is developed by the developing roller 7. On the other hand, the transfer material P loaded in the paper cassette 14 is fed by the paper feed roller 12, and the registration roller 12
sent to.

The transfer material P is waiting with its leading end bitten by the registration roller 11, and is sent to the transfer roller 10a to transfer the image in synchronization with the image written on the photosensitive drum 2. The toner 8 transferred to the transfer material P is fixed by a fixing device 15, and the transfer material P is discharged to the outside of the machine by a discharge roller 16.

On the other hand, the toner 8 remaining on the photosensitive drum 2 after being transferred is
is cleaned by the cleaner 9 and moves on to the subsequent process.

In the image forming apparatus configured as described above, when the environmental information of the transfer means is detected at a predetermined timing after the start of printing, the transfer bias setting means (in this embodiment, the transfer bias setting means provided in the mechanical control section 26) is activated. The bias setting unit 26a) sets a desired transfer bias to the transfer means (transfer roller 10a) one or more times, and always sets the desired transfer bias that is optimal for the environmental condition of the transfer means.

Further, the transfer bias setting means sets a desired transfer bias based on the environmental information of the transfer means detected during a predetermined pre-rotation process at the start of continuous printing, and sets a desired transfer bias at the start of continuous printing. Set the desired transfer bias that is optimal for printing.

FIG. 2 is a block diagram illustrating the control configuration of the image forming apparatus shown in FIG. 1, and the same components as in FIG. 10 are given the same reference numerals. 26a is a transfer bias setting section.

The prefeed printing process in the image forming apparatus shown in FIG. 1 will be described below with reference to FIG. 3.

FIG. 3 is a timing chart illustrating a prefeed print processing sequence in the image forming apparatus shown in FIG. Note that the prefeed print processing sequence is controlled by the mechanical control section 26.

Now, main unit 1 receives three pages of code data between timing (a) and timing (b), between timing (i) and timing (j), and between timing (p) and timing (q). This will be explained below.

First, in a control unit (for example, the microprocessor 17 shown in FIG. 10), timing (a) to timing (
Image development of the first page code data received during b) is started. When the reception of the first page code data is completed, the drum drive starts at timing (C), the scanner starts rotating, and the laser beam printer main body 1
operation begins.

Next, a series of print preparation operations called pre-rotation are performed. In the pre-rotation, primary charging and transfer bias are set, the charging state of the surface of the photosensitive drum 2 is made uniform, and the output of the laser scanner 3 is adjusted.

After the drum drive starts at timing (C), the main body 1 performs a paper feed pickup operation at timing (d) before laser exposure (f) starts. The transfer material P is conveyed and waits with its leading end bitten by the registration rollers 11. As a result, it becomes possible to transport the transfer material P in synchronization with laser exposure. The image development on the first page is the timing (
If the above-mentioned pre-rotation is not completed even if it ends in e),
The transfer material P waits at the position of the registration roller 11 without image data reading (laser exposure), and when the pre-rotation is completed, image data reading starts at timing (f).

As the image data is read out, the image is written onto the photosensitive drum 2 by the laser scanner 3. The transfer material P, which is already waiting at the position of the registration roller 11, is synchronized with the rotation of the photosensitive drum 2. The registration roller 11 is driven at a timing (g) delayed by the difference in time for the transfer material P to move from 11 to the transfer position I22 (usually at a constant speed, so this is a length difference).

Here, it goes without saying that if 12I<12x, the leading edge of the image will be missing.

When the electrostatic latent image written on the photosensitive drum 2 by laser exposure comes to the development position, a development bias is applied and development is performed. When the reading of the image data of the first page is completed (timing (h)), timing (i) to timing (h)
), image development for the second page begins.

At this time, the microprocessor 17 has received the code data for the second page, so it starts picking up the paper feed for the second page at timing (k) while reading the image data for the first page. Image data read timing (h
), and at the same time, image development of the code data of the second page is performed between timing (h) and timing (2).

If the image development is completed quickly, then the printing operation continues, but if it takes a long time, the photosensitive drum 2 enters a series of operation modes called post-rotation.
The transfer bias is turned off, the surface of the photosensitive drum 2 is brought to a uniform potential by only negative charging, the printed transfer material P is discharged outside the machine, and the drum drive is stopped. after that,
The image development on the second page is from timing (h) to timing (I
When step 2) is completed and the printing operation begins, the photosensitive drum 2 is driven again and enters the pre-rotation operation, but at this time,
Since the transfer bias set during the previous rotation of the first page is retained, the transfer bias setting mode may not be executed.

Therefore, throughput is improved by this shortened time. Since the CPU 17 has received the code data of the third page, when reading the image data of the second page (timing (m) to timing ('o)), 3
The paper feed pickup for the page is performed.

Then, at the end of reading (timing (0)), image development for the third page is started. When the image development takes a long time, 2
The printing operation for the page enters backward rotation and the drum drive is stopped. Then, when the image development for the third page is completed (timing (1)), a pre-rotation that is shorter than the pre-rotation for the first page is performed as in the case of the second page, and the image data is read out at timing (V). Then, printing on the transfer material P is started at timing (w).

Since the printer has not received the code data for pages 3 and onwards, the paper feeding operation for the 4th page is not performed, and when the image is transferred to the transfer material P for the 3rd page, it enters a post-rotation operation and the transfer bias is is turned off, the surface of the photosensitive drum 2 is brought to a uniform potential by only the negative charge, and the transfer material P is discharged outside the machine.

Then, the drum drive and scanner rotation stop, and the printer stops.

Transfer bias setting mode processing in the image forming apparatus according to the present invention will be described in detail below.

In this embodiment, the transfer roller is controlled with a constant current during pre-rotation during printing, and the generated voltage is temporarily held and applied when printing on the transfer material P.

In particular, the transfer roller 10a employed in this embodiment is an EEPDM foam sponge roller, for example, an 8oφ S
It is constructed with a wall thickness of 6t on a US core metal, and its actual resistance value is 1.
It is controlled in the range of 08 to 109Ω. Hardness is AS
The KER-C hardness is 30°.

A prefeed command is issued when the code information is entered into the microprocessor 17, and the paper is fed and picked up at timing (d) as soon as the photosensitive drum 2 starts rotating forward. During the pre-rotation of the photosensitive drum 2, the aforementioned transfer roller 10a
is controlled at a constant current, and the voltage generated at that time is held and applied during printing. In this embodiment, the process speed is 50 mm/sec, and the transfer roller 10a is controlled at a constant current of -700 V and 4 .mu.A, so that the potential on the photosensitive drum 2 during the previous rotation is a dark potential v0 of -700 V and 4 .mu.A.

The current value of 4 μA is determined from the resistance value of the transfer roller 10a and the load impedance of the photosensitive drum 2, and if the current value is smaller than the above-mentioned current value, a transfer failure is likely to occur.
This is particularly noticeable in low humidity environments.

In addition, if the current value is larger than the above value, an excessive charge with a characteristic opposite to that of charging is applied to the photosensitive drum 2, causing it to be charged in the opposite direction, forming a positive memory, and achieving the desired charge in the next stage of primary charging. The voltage does not recover to the potential, resulting in charging failure during printing, resulting in fog on the image.

Therefore, in this embodiment, when the above constant current control is performed in the transfer roller 10a, the normal environment (23° C., 60%
RH: N/N), approximately 2.5 KV, and 3.5 KV in a low temperature, low humidity environment (15°C, 10% RH: L/L). OKV, approximately 2 in a high temperature and high humidity environment (32℃, 85%RH: H/H)
．． A voltage of OKV is generated, and a good transfer image can be written under various environments.

Note that in this embodiment, when printing multiple sheets, 1
The above-mentioned control is performed during the pre-rotation when printing the first sheet, and the transfer bias is set during subsequent printing, and the transfer bias is held until the pre-feed signal is reset.

Therefore, when printing the second and subsequent sheets, it is possible to shorten the pre-rotation time, thereby improving throughput. Furthermore, since the transfer roller 10a is employed, it is possible to obtain good transfer performance in various environments without being affected by deformation or bending of the transfer material at the registration roller nip portion.

In the above embodiment, the transfer bias is set only when the pre-rotation process is executed when printing the first page, and the print process is thereafter executed based on the set transfer bias. If image development for subsequent printing is not completed within a predetermined time, the transfer bias may be reset once and the transfer bias setting mode may be implemented when the printing operation is started again.

[Second Embodiment] FIG. 4 is a sectional view illustrating the configuration of an image forming apparatus showing a second embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the figure, reference numeral 13a denotes a paper leading edge detection sensor, which is disposed downstream of the conveyance roller (registration roller) 11. In this embodiment, the drive system for the photosensitive drum 2 and the conveyance system for the transfer paper P are each driven by independent drive means.

FIG. 5 is a block diagram illustrating the control configuration of the image forming apparatus shown in FIG. 4, in which a controller mainly processes image information such as receiving code data of an image from a host and developing an image of the code data. section 100 and a printer section 101 that controls the operation of the laser beam printer main body 1. The controller section 100 includes an I10 shown in FIG.
Driver 23. It is equipped with a Rask conversion circuit 24 and the like, and a single-chip microcomputer 40 functions as a mechanical control section 26.

In the image forming apparatus configured as described above, the transfer bias setting means (in this embodiment, the single-chip microcomputer 40 also serves as the single-chip microcomputer 40) performs the desired transfer based on the pixel conversion elapsed time by the pixel conversion means (Rask conversion circuit 24). The bias is reset to set an optimal desired transfer bias that allows an optimal image to be obtained even if the elapsed pixel conversion time extends over a long period of time.

Single chip microcomputer (microcomputer) 40
The loads include a drum drive motor driver 41a, a conveyance motor driver 41b, and a laser scanning motor driver 4.
3. Paper feed clutch 45. Conveyance roller clutch 469 Paper leading edge detection sensor 47° High voltage output circuit 48. Laser modulation circuit 49. Controls the beam detection circuit 51 and the like.

A ready signal READY, a print signal PRINT, a vertical synchronization request signal VSREQ, a vertical synchronization signal VSYNC, a prefeed signal PRFD, etc. are sent between the microcomputer 40 and the I10 driver 23 to control the printer engine. Enter 17.

In addition, I10 Dryno (23
A serial communication line for notifying the microcomputer 4o of special commands from the I10 driver 23 is also easily provided.

In addition, the image signal V output from the rask conversion circuit 24
I DEO is input to the laser modulation circuit 49, which modulates the light output from the semiconductor laser 50 according to the image signal V I DEO. The laser beam is scanned by a laser scanning mirror, and the scanned laser beam is incident on the photodiode 52. And the beam detection circuit 51
The laser beam is converted into a pulse signal and input to the Rask conversion circuit 24 as a horizontal synchronization signal HSYNC.

The operation of the second embodiment will be described below with reference to the timing chart shown in FIG.

FIG. 6 is a timing chart illustrating a second transfer bias setting mode processing operation in an image forming apparatus showing a second embodiment of the present invention.

When the printer unit is powered on and can receive print signals at any time, the ready signal READY is T.
It is RUE. In this state, the controller unit 100
After receiving one page of code data between timings (a) and (b), the print signal PRINT is sent to the printer unit 101 at timing (e), and the prefeed signal PRFD is sent to the printer unit 101 at timing (C). be done.

In response to this, the printer unit 101 determines the timing (eo
), the drum drive (pre-rotation) is started, and - next charging, setting of transfer bias, paper feed pickup, etc. are performed in sequence to prepare for receiving and receiving image signals.

In this embodiment, the transfer bias setting method is the same as that in the first embodiment, so a description thereof will be omitted.

Paper feeding is picked up at timing (d) by the prefeed signal PRFD, and when the leading edge of the transfer material P reaches the paper leading edge detection sensor 13a, the photo sensor output also becomes TRUE at timing (h), and the image signal is accepted. The controller unit 100
The vertical synchronization request signal VSREQ notified to the timing (
i) becomes TRUE.

In response to this vertical synchronization request signal VSREQ, the controller section 100 side outputs a print signal PRIN after image development is completed.
T is output, and the printer unit 101 enters the pre-rotation operation. Then, the vertical synchronization signal VSYNC that notifies the readout of image data from the controller unit 100 side is at timing (j).
The image signal VIDEO is sent to the printer unit 101 between timing (k) and timing (0).

When the printer unit 101 receives the vertical synchronization signal VSYNC, the transfer material P that was waiting is fed by re-driving the conveyance roller 11, and the timing is set so that the leading edge of the image and the leading edge of the transfer material P are synchronized. The image is then conveyed toward the photosensitive drum 2 and transferred by the transfer roller 10a.

Since the controller unit 100 receives the second page code data between timing (f) and timing (g), the prefeed signal PRFD is in the TRUE state. Therefore, while the controller unit 100 is in the process of reading out the image data of the last page, the printer unit 100
1, the second page is fed at timing (m).

When the second page is fed, the controller unit 100
Since the page code data has not been received, the timing (
m) becomes a FALSE state.

When the reading of the image data of the first page is completed (timing (0)), the printer unit 101 enters step and rotation, and the photosensitive drum 2 stops driving, and the controller unit 100 starts image development of the second page at timing (p ) ~ timing (s
).

The pre-fed transfer material P is detected by the paper leading edge detection sensor 13a.
When it reaches TRU, the output of the paper leading edge detection sensor 13a becomes TRU.
E, and the vertical synchronization request signal 5REQ becomes TRUE (timing (r)).

If it takes time to develop the image, the printer section 101 maintains this state and waits for the vertical synchronization signal VSYNC from the controller section 100.

At this time, if the image development process takes longer than a predetermined time T, the transfer bias held during the previous rotation when printing the first page is reset once, and after the image development is completed (timing (S)), a new This is where the transfer bias setting mode is executed.

In Fig. 6, image development processing time (timing (p)
~Timing (S)) is listed, a certain time T
Afterwards, the transfer mode reset signal becomes TRUE, the transfer bias held during the previous rotation of the first page is reset, and a mode is implemented in which the transfer bias is set again during the next printing.

The transfer bias mode setting operation during the pre-rotation will be described below with reference to the characteristic diagram of the image development processing time for the recording medium shown in FIG.

FIG. 7 is a characteristic diagram showing the state of page development processing in the image forming apparatus according to the present invention, in which the horizontal axis shows the elapsed time t (minutes) since the microcomputer 40 starts image development, and the vertical axis shows code information. The ratio R (%) of the data that has been converted from to pixel information to the image data capacity for one page is shown. Note that the solid line in the figure indicates in advance the threshold value Rth(t) for determining whether or not the transfer bias setting mode is enabled.

The microcomputer 40 monitors the amount of data stored in the image data storage memory 20 from the start of pixel development, and thereby, the amount of data that has been converted from code information to pixel information.
Find the ratio R (%) to the image data capacity for a page,
This ratio R is compared with the threshold value Rth for determining whether or not the transfer bias setting mode can be used, and if the ratio R is lower than the threshold value Rth even after a certain period of time T (minutes) has passed, the image development will take a long time. , the set transfer bias is reset, and the transfer bias setting mode is performed during the pre-rotation for the next printing.

That is, as shown in FIG. 7, the actual image development characteristic R(
t) When the development process shown in (indicated by the broken line in the figure) is executed, if it is determined that the transfer material P has remained in the standby position for more than 30 minutes, the above-mentioned transfer bias setting mode process is executed. .

As a result, when significant environmental changes occur, such as the morning environment of the second chair, or sudden changes in the heating and cooling system, the optimal transfer bias is automatically set, resulting in good image quality. Print images can be obtained.

In addition, in the above embodiment, if the image development of the second and subsequent pages is not completed within a predetermined time, the transfer bias is reset once and the transfer bias setting mode is executed when the printing operation starts again. but,
The transfer bias setting mode process may be controlled to be executed at the time when the prefeed signal PRFD is sent to the printer section 101.

[Third Embodiment] FIG. 8 is a timing chart illustrating a third transfer bias setting mode processing operation in an image forming apparatus showing a third embodiment of the present invention. In addition.

Since the hardware configuration and control configuration are the same as those in the second embodiment, explanations of the hardware configuration and control configuration will be omitted.

In the image forming apparatus configured as described above, a transfer bias setting means (in this embodiment, the microcomputer 40 also serves)
The desired transfer bias is set at the time of a pre-feed paper feeding request to the paper feeding means, and the setting of the transfer bias is completed before the start of a predetermined pre-rotation process.

When the printer unit 101 is powered on, the ready signal READY is in the TRUE state, and the printer unit 101 is ready to receive the print signal PRINT at any time. When the controller unit 100 starts receiving one page of code data in this state, a prefeed signal PRFD is sent to the printer unit 101 at timing (e).

In response to this, the printer unit 101 determines the timing (e
Drum driving is started at step o), and -order charging, setting of transfer bias, and sheet feeding pickup (timing (d)) are started.

The above transfer bias setting conditions are as follows. This is similar to the second embodiment, but in this embodiment, the drum is driven in a mode for setting the transfer bias. may overlap.

In such a case, priority is given to drum driving in the transfer bias setting mode, and control is performed so that the pre-rotation operation is subsequently started.

Therefore, it is desirable to set the transfer bias setting mode to the optimum transfer bias value in the shortest possible time. In this embodiment, in order to correct variations in the generated voltage due to unevenness in the circumferential direction of the transfer roller 10a, the microprocessor 17 samples the generated voltage over one rotation of the transfer roller 10a, and sets the average as the transfer bias.

By using such a print sequence, even when the image development is completed in a very short time, the first... The first print can be performed in about the same amount of time as the pre-rotation operation before printing described in the second embodiment.

In addition, if the image exhibition is for a long period of time, the transfer bias is set in advance, so as in the first embodiment, the pre-rotation time before printing can be shortened, and when continuous printing is performed, it is possible to prevent a drop in throughput. Effective.

Further, in this embodiment, since the drum drive and paper feeding operation are performed by separate drive motors (for example, step motors), it is possible to drive the drum and advance paper feeding. Therefore, in the same drive, the first sheet of paper is fed after the print signal is input, but in this embodiment, even if the print signal is not sent out, the prefeed signal PRF
Since the paper is fed at D, the transfer material is already in the standby position even when the first image development chart is drawn, and the pre-rotation time is short (
Since it is possible to increase the throughput from the first sheet. Sometimes,
In this example, even if the first image is developed face-up,
Since the transfer bias is set in advance, the pre-rotation operation can be shortened and the throughput can be further improved.

[Effects of the Invention] As explained above, the present invention sets a desired transfer bias to the transfer means at least once or more based on the environmental information of the transfer means detected at a predetermined timing after the start of the print sequence. Since the transfer bias setting means is provided, it is possible to set the desired transfer bias in the transfer means according to the print sequence situation, so even if environmental changes occur in the transfer means according to the print sequence situation, the optimum transfer bias can be set, and the transfer An optimally developed image with no defects can be transferred to a recording medium.

In addition, the transfer bias setting means is configured to set a desired transfer bias based on the environmental information of the transfer means detected during a predetermined pre-rotation process at the start of continuous printing, so that the transfer bias can be set according to the print sequence situation. Even if environmental changes occur in the means, an optimal transfer bias can be set without reducing throughput, and good developed images without transfer defects can be continuously transferred to a recording medium.

Furthermore, the transfer bias setting means is configured to reset the desired transfer bias based on the elapsed time of pixel conversion by the pixel conversion means, so even if the print sequence is interrupted for a long time, the transfer white Situations such as omissions and transfer defects can be prevented, and optimally developed images can always be stably transferred to recording media.

Furthermore, the transfer bias setting means is configured to set a desired transfer bias when a pre-feed paper feed request is made to the paper feed means, so that the transfer bias setting can be started in synchronization with the pre-feed paper feed request. Transfer bias setting processing can be completed while minimizing deterioration.
Pre-rotation time can be shortened as much as possible.

Therefore, excellent effects such as transfer bias setting processing for forming a clear image without transfer defects or transfer white spots can be performed at optimal timing and without reduction in throughput.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating the configuration of an image forming apparatus showing a first embodiment of the present invention, FIG. 2 is a block diagram illustrating the control configuration of the image forming apparatus shown in FIG. 1, and FIG. 4 is a timing chart explaining the pre-feed print processing sequence in the image forming apparatus shown in FIG.
FIG. 5 is a cross-sectional view illustrating the configuration of an image forming apparatus showing a second embodiment of the present invention, FIG. 5 is a block diagram illustrating the control configuration of the image forming apparatus shown in FIG. 4, and FIG. FIG. 7 is a timing chart illustrating the processing operation of the second transfer bias setting mode in the image forming apparatus according to the second embodiment of the invention; FIG. FIG. 9 is a timing chart illustrating a third transfer bias setting mode processing operation in an image forming apparatus according to a third embodiment of the present invention; FIG. 9 is a sectional view showing an example of the configuration of a conventional image forming apparatus; FIG.
11 is a block diagram showing a control configuration in the image forming apparatus shown in FIG. 9, FIG. 11 is a timing chart showing a print sequence in the image forming apparatus shown in FIG. 9, and FIGS. 12 and 13 are FIG. 2 is a cross-sectional view of a main part showing a state in which a transfer material is fed in a conventional image forming apparatus. In the figure, 2 is a photosensitive drum, 10a is a transfer roller, 26 is a mechanical control section, and 26a is a transfer bias setting section. Figure 7 n, XJ-D-t3sv+'>lSC>% Figure 9 Figure 12

Claims (4)

[Claims] (1) A transfer means for transferring a toner image developed by contacting a photoreceptor onto a transfer material, a receiving means for receiving predetermined code information in which character or graphic information is encoded, and a receiving means for receiving predetermined code information encoded with character or graphic information; A pixel conversion means that converts into pixel information, an image forming means that forms an image on a transfer material based on the pixel information, and a pixel conversion means that moves the transfer material to a predetermined position at an arbitrary timing independent of whether or not pixel conversion processing is performed by the pixel conversion means. In an image forming apparatus having a paper feeding means capable of pre-feeding paper until the print sequence is started, a desired transfer bias is set based on environmental information of the transfer means detected at a predetermined timing. An image forming apparatus characterized by comprising a transfer bias setting means for setting the transfer bias at least once or more. (2) The transfer bias setting means sets a desired transfer bias based on environmental information of the transfer means detected during a predetermined pre-rotation process at the start of continuous printing. image forming device. (3) The image forming apparatus according to claim 2, wherein the transfer bias setting means resets the desired transfer bias based on the elapsed time of pixel conversion by the pixel conversion means. (4) The image forming apparatus according to claim 1, wherein the transfer bias setting means sets a desired transfer bias when a pre-feed paper request is made to the paper feed means.