JPH09127847A - Color laser printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high definition color image by counting the rotation time of an intermediate transfer body at the time of executing a printing process, from the execution of a consecutive printing process and a nonprinting stand-by state and feedback-controlling the rotational speed of the intermediate transfer body. SOLUTION: When the time (tw) of the nonprinting standyby state is a specified time or more, the rotation time tf of an intermediate transfer drum is counted before an electrostatic latent image of the first color Y for the next printing is formed. The time tf is compared with the rotation reference time TO of the intermediate transfer drum and a photoreceptive belt driving motor speed setting value FO' is corrected to correct a time shift from the rotation reference time TO. Then, the speed setting value FO" after being corrected is used as the speed setting value at the time of forming the electrostatic latent image of the first color Y for the next printing. On the other hands, when the time tw is the specified time or less, the speed setting value at the time of forming the electrostatic latent image of the first color Y for the next printing is executed at the speed setting value FO' by the previous printing command, to enable following up change in the rotational characteristic of the intermediate transfer drum caused by the change in the dimension of a rotary driving system for a photoreceptive belt and the intermediate transfer drum due to the rising of a temp. in a machine, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer, and more particularly to a color printer which obtains a color image by superimposing and transferring different color toner images on an intermediate transfer member.

[0002]

2. Description of the Related Art A conventional color laser printer is of a type that forms a color image by transferring a plurality of different-color toner images formed on a photoconductor onto an intermediate transfer body in an overlapping manner. In the above-mentioned method, a photoconductor including a photoconductive photoconductive drum or photoconductive belt is rotated at a predetermined speed to uniformly charge the surface of the photoconductor, and is deflected and scanned in a direction perpendicular to the rotational direction of the photoconductor. The exposure control for forming an electrostatic latent image is performed by intermittently controlling the laser beam according to the video data corresponding to the image for each color to be printed. The electrostatic latent image formed on the surface of the photoconductor by exposure is developed to form a toner image, and the toner image is transferred to an intermediate transfer member that rotates while partially contacting the photoconductor. A color toner image is formed on the intermediate transfer member by repeating the above process a plurality of times. The color toner image formed on the intermediate transfer member is collectively transferred to a sheet and then fixed to realize color image printing. in this way,
In a laser printer including a photoconductor and an intermediate transfer member, the positioning accuracy of the toner images of the respective colors on the intermediate transfer member is an important issue in obtaining a high-definition color image. Therefore, as described in JP-A-62-195687, each driving means for driving the photoconductor and the intermediate transfer member is controlled in synchronization with a common basic clock signal, and the basic clock signal is used. A control means for controlling the exposure and transfer timing of each color has been proposed. In addition, JP-A-63-81
As described in Japanese Patent No. 370, a photosensitive drum driving means is provided which detects the speed of a transfer paper conveying belt which is brought into contact with a plurality of photosensitive drums each having a developing device one after another, and which rotates following the photosensitive drums. Color printers have been proposed to control the speed of the.

[0003]

In the speed control of the photoconductor in the conventional color printer, a slight dimensional change of the rotary drive portion, which directly affects the rotational speeds of the photoconductor and the intermediate transfer member, is caused by the temperature rise in the apparatus. As a result, the preset rotation speed of the photosensitive member and the preset rotation time of the intermediate transfer member deviate from each other. As a result, a positional shift occurs between the electrostatic latent image of the previous color and the electrostatic latent image of the previous color in the page, and the alignment accuracy of the toner image deteriorates.

An object of the present invention is to provide a color printer provided with a drive control device which optimizes the speed control method of the photosensitive drum rotation drive means in order to improve the above-mentioned problems.

[0005]

According to the present invention, the rotation time of an intermediate transfer member is measured in speed control of a photosensitive member, and the time difference is calculated by comparing the measurement result with the rotation reference time of the intermediate transfer member. A control means is provided for changing the speed of the photosensitive member in the color superimposing process during printing in the direction of correcting the rotation time difference. Further, when the non-printing standby time has exceeded the predetermined time, the rotation time of the intermediate transfer member is measured before the formation of the electrostatic latent image of the first color for the next printing, and the time difference from the rotation reference time is corrected. A control drive circuit for changing the speed of the photoconductor in the direction of rotation is provided.

As described above, when the non-print waiting time has exceeded the predetermined time, the rotation time of the intermediate transfer member is measured before the formation of the electrostatic latent image of the first color for the next printing, and the rotation time difference is calculated. By changing the rotation speed of the photoconductor in the direction to be corrected, the rotation time deviation due to the minute dimension change due to the temperature rise of the rotation drive section of the photoconductor and the intermediate transfer body can be corrected by optimizing the rotation speed of the photoconductor. You can This makes it possible to form a toner image on the intermediate transfer member with improved color superposition accuracy.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the photosensitive belt is used as the photosensitive member and the intermediate transfer drum is used as the intermediate transfer member. However, it goes without saying that the photosensitive member may be a drum and the intermediate transfer member may be a belt. Nor.

FIG. 1 shows a cross section of the main part of a laser printer. The printing portion of the laser printer 27 includes a photosensitive belt 5 wound around the rotating wheels 1 and 2 so as to rotate at a constant speed in the arrow direction, and rotating wheels 1 and 2 for rotating the photosensitive belt 5. A photosensitive belt drive motor 6 for driving the
A position sensor 14 for reading a reference position mark formed on the outer peripheral surface of the photosensitive belt 5 in order to generate a reference position signal for the photosensitive belt 5 and a charger 7 for uniformly charging the surface of the photosensitive belt 5. A scanning exposure device 8 that exposes the uniformly charged surface of the photosensitive belt 5 to form an electrostatic latent image on the surface of the photosensitive belt 5, and four scanning exposure devices that develop the electrostatic latent image to form a toner image. The developing devices 9, 10, 11, 12 are provided with a cleaner 13 for removing the toner remaining on the surface of the photosensitive belt 5 after the transfer of the toner image, and an erase lamp 17 for removing the electric charges remaining on the surface of the photosensitive belt 5. The scanning exposure device 8 is configured to irradiate the surface of the photosensitive belt 5 with a laser beam 39 according to video data and expose the surface of the photosensitive belt 5 by scanning the laser beam 39. The scanning exposure device 8 detects the timing when the beam spot passes the deflection scanning start reference position in each deflection scanning.

The developing units 9, 10, 11 and 12 are four developing units respectively using four color developers, and each developing unit 9, 10, 11, 12 is controlled by controlling a developing bias voltage. The developing function is imparted or lost. The intermediate transfer drum 15 is used to superimpose a plurality of toner images of different colors formed on the surface of the photosensitive belt 5 to form one color toner image and transfer the formed color toner image to a sheet.

The intermediate transfer drum 15 uses the photosensitive belt drive motor 6 as a drive source, and the driving force is transmitted by frictional force and electrostatic attraction force at one contact portion with the photosensitive belt 5, and the surface of the photosensitive belt 5 is moved in the arrow direction. It rotates at a speed synchronized with.

Further, in order to remove the toner remaining on the surface of the intermediate transfer drum 15, a cleaner 16 capable of controlling contact and separation is arranged on the surface of the intermediate transfer drum 15.

A reference position mark is formed on the outer peripheral surface of the intermediate transfer drum 15, and a position reference sensor 23 generates a read reference position signal TPS. Further, the outer peripheral surface and the like are configured such that the deflection scanning start reference detection signal BDT1 output from the scanning exposure device 8 is always generated an integral number of times during the period in which the intermediate transfer drum 15 makes one rotation. Cassette 1
8 stores the paper 19, the paper feed roller 20 extracts the paper 19 and supplies it to the registration roller 21, and the registration roller 21 temporarily stops the conveyance of the paper 19 sent by the paper feed roller 20 to perform alignment. Adjust the paper feed timing.

The transfer device 22 applies transfer charge to the back surface of the paper 19 in a region where the paper 19 conveyed from the registration rollers 21 contacts the intermediate transfer drum 15 to form a toner image on the surface of the intermediate transfer drum 15. Transfer to No. 19. Further, the static eliminator 23 separates the paper 19 from the surface of the intermediate transfer drum 15.

The fixing device 24 is configured to fix the toner image on the paper 19 by passing the paper 19 on which the toner image is transferred between the heating roller and the pressure roller.

The paper discharge roller 25 is for discharging the paper on which the toner image is fixed to the outside of the machine. The control device 26 is connected to a higher-level information processing device, exchanges control information and print data with the information processing device, and controls the constituent means inside the laser printer 27 to execute printing.

FIG. 2 is a block diagram describing the internal configuration of the control device 26. The control device 26 is mainly composed of a CPU 28, and has a ROM 40, which stores a control program,
A RAM 37 for storing control parameters, a laser control circuit 29 for controlling blinking of the semiconductor laser 8a, a beam detector / amplifier circuit 8g for detecting a timing at which a beam spot passes a deflection scanning start reference position, the deflection scanning start reference. The scanning reference signal generating circuit 30, which generates a scanning synchronization reference signal based on the detection signal BDT1 and the reference position signal HPS in the sub-scanning direction, the oscillator 31, and the reference position signal TPS of the intermediate transfer drum 15 are input to the intermediate transfer drum 15. Signal processing circuit 33, CP for measuring the rotational speed of
A clock supply circuit 34, which is a photosensitive belt drive motor rotational speed adjustment unit that controls a rotational speed of a photosensitive belt by supplying a reference clock signal that is a reference of rotational speed to a photosensitive belt control drive circuit controlled by U28. The oscillator 32 and the control drive circuit 35 for controlling the components inside the laser printer 27 are provided.

Next, the print control process executed by the CPU 28 will be described with reference to FIG. When the information processing device generates a print request signal, the CPU 28 in the control device of the laser printer 27 responds to the print request signal by the ROM 4
The print control process according to the control program stored in 0 is started.

First, the control drive circuit 35 is operated to rotate the photosensitive belt 5 and the intermediate transfer drum 15, and the erase lamp 17, the charger 7 and the transfer device 22 are put into operation. Next, the developing devices 9, 10, 11, 12 to be operated are confirmed based on the information given from the information processing device.

The input of the reference position signal HPS in the sub-scanning direction on the surface of the photosensitive belt 5 is monitored, and the photosensitive belt 5 rotates to the writing reference position and the reference signal HPS in the sub-scanning direction.
Occurs, the print permission signal in the sub-scanning direction is output after T1.
Generate Vsync.

In the sub scanning direction print permission signal Vsync generation period, the main scanning direction print permission signal Hsync is generated after a predetermined time from the generation timing of the main scanning synchronization reference signal BDT1.

Thereafter, the video data transmitted from the information processing device is received in synchronization with the generated print permission signal Vsync in the sub-scanning direction, transmitted to the laser control circuit 29, and the semiconductor laser 39 is controlled to blink. An electrostatic latent image for one scanning line is formed on the surface of the photosensitive belt 5 by the semiconductor laser blinking control.

When the electrostatic latent image for one scanning line is completed, it is confirmed whether or not it is within the print permission signal Vsync generation period T2 in the sub-scanning direction, and the print permission signal Vsync generation period T2 in the sub-scanning direction is confirmed.
Within the range, the generation of the main scanning synchronization reference signal BDT1 is monitored, and when the next main scanning synchronization reference signal BDT1 is generated,
The video data transmitted from the information processing device is received in synchronization with the print permission signal Vsync in the sub-scanning direction, transmitted to the laser control circuit 29, and the semiconductor laser 8a is controlled to blink.

When the print permission signal Vsync generation period T2 in the sub-scanning direction ends, the print permission signal Vsync in the sub-scanning direction disappears, the exposure of the toner image of the corresponding color ends, and the electrostatic latent image formed by the exposure. The developing device 9 of the corresponding color,
After development by 10, 11, and 12, the developing function of the developing device is lost after development.

The toner image of the corresponding color thus formed is transferred and held on the surface of the intermediate transfer drum 15 when coming into contact with the intermediate transfer drum 15. In the printing process for the two colors or later, instead of the input waiting process of the reference position signal HPS in the sub-scanning direction, the print permission signals Hsync, V in the main-sub-scanning direction for the time T0 when the intermediate transfer drum 15 makes one revolution
sync Difference Tr between total occurrence period T1 and T2 and T1 + T2
Is controlled to perform the above-described exposure and development operations.

In this way, the toner images of two or more colors are also transferred and held on the surface of the intermediate transfer drum 15 so as to be superimposed on the toner image of the previous color.

In this way, in order to transfer the toner image on the surface of the intermediate transfer drum 15 to the paper 19, the paper feed roller 20 is rotated to extract the paper 19, the paper 19 is supplied to the registration roller 21, and the paper feed roller 21. Stop rotating.

Next, the sheet feeding timing is set so that the sheet 19 aligns with the toner image and comes into contact with the intermediate transfer drum 15, and the leading edge of the sheet 19 conveyed by the rotation of the registration roller 21 becomes the intermediate transfer drum 15. The transfer device 22 is energized at the timing when the intermediate transfer drum 1 comes into contact with the intermediate transfer drum 1.
5 The toner image on the surface is electrostatically transferred to the paper 19.

Further, the paper 19 on which the color toner image is transferred has the toner image on the paper 1 while passing through the fixing device 24.
The sheet is fixed on the sheet No. 9, and is ejected outside the apparatus by the sheet ejection roller 25.

Next, referring to FIGS. 4 and 5, the color superposition speed control method by the photosensitive belt driving means according to the present invention will be described.

As described with reference to FIG. 3, in order to accurately form the color superposed toner image on the intermediate transfer drum, the electrostatic latent image formed on the photosensitive belt at the electrostatic latent image cycle time (T0) is formed. The developed toner image must be accurately intermediate-transferred for each rotation of the intermediate transfer drum.

First, the speed control method of the photosensitive belt drive motor in the four-color (YMCK) overprinting process during continuous printing without the non-printing standby state will be described with reference to FIG.

The photosensitive belt speed control at the time of forming the electrostatic latent images of the first color (Y) and the second color (M) is controlled by the preset photosensitive belt drive motor speed set value F0. During the formation of the electrostatic latent image of the third color (C), the diameter of the intermediate transfer drum increases due to the adhesion of the toner image to the intermediate transfer drum 15, and the intermediate transfer drum 1 driven by the photosensitive belt.
One rotation time of 5 will increase. In consideration of this, the speed setting correction value f is set to the photosensitive belt drive motor speed setting value F0.
The speed is controlled by the photosensitive belt drive motor speed setting value F1 (= F0 + f) to which is added (correction amount corresponding to rotation time delay due to increase in diameter of intermediate transfer drum due to adhesion of toner image). When the electrostatic latent image of the fourth color (K) is formed, it is controlled by the photosensitive belt drive motor speed setting value F2 (= F1 + f) to which the speed setting correction value f is further added. Further, the rotation time of the intermediate transfer drum is measured at the timings shown in the figure in parallel with the electrostatic latent image forming processing of four colors.

After the formation of the four-color electrostatic latent image, the rotation measurement time t2 for one rotation of the intermediate transfer drum 15 at the time of forming the latent image of the fourth color is compared with the intermediate transfer drum rotation reference time T0.
The photosensitive belt drive motor speed set value F0 is corrected so as to correct the time lag from T0, and the corrected photosensitive belt drive motor speed set value F0 'is executed as the photosensitive belt speed set value for the next printing. Thereafter, the photosensitive belt drive motor speed control is executed for each print page.

The speed switching timing by the speed control of the photosensitive belt driving motor is performed at the end of the formation of the electrostatic latent image of each color.

Next, a speed control method of the photosensitive belt drive motor in the four-color (YMCK) overprinting process in the case where the print command is intermittently issued and the non-print standby state continues, will be described with reference to FIG. To do.

After the completion of the four-color (YMCK) overprinting process according to the previous print command, if the time (tw) in the non-print standby state until the next print command is issued is a predetermined time or more, the next print The rotation time (tf) of the intermediate transfer drum is measured before the electrostatic latent image of the first color (Y) is formed. Then, the rotation measurement time tf for one rotation of the intermediate transfer drum is compared with the intermediate transfer drum rotation reference time T0, and the photosensitive belt drive motor speed set value F0 'is corrected so as to correct the time lag from T0. The corrected photosensitive belt drive motor speed set value F0 ″ is executed as the photosensitive belt drive motor speed set value when the electrostatic latent image of the first color (Y) of the next printing is formed.

On the other hand, when the time (tw) in the non-printing standby state until the next print command is issued after the completion of the four-color (YMCK) overprinting process by the print command is less than the predetermined time, the next print The photosensitive belt drive motor speed setting value at the time of forming the electrostatic latent image of the first color (Y) is executed by the photosensitive belt drive motor speed setting value F0 ′ at the time of executing the four-color overprinting process by the previous print command. .

By the above control processing, it is possible to follow the change in the rotational characteristic of the intermediate transfer drum due to the dimensional change of the rotational drive system of the photosensitive belt 5 and the intermediate transfer drum 15 caused by the temperature rise in the apparatus, and the sub scanning direction. The positional deviation of the toner images of plural colors can be eliminated on the intermediate transfer drum 15.

[0039]

According to the present invention, the intermediate transfer member is rotated by a driving force obtained by a frictional force or an electrostatic adsorption force from one contact portion with the photosensitive member, so that the intermediate transfer member is rotated by an environment and a change with time. In consideration of fluctuations, the intermediate transfer body rotation time during continuous printing process execution and during printing process execution from the non-printing standby state is measured, and the rotational speed of the intermediate transfer body is feedback-controlled so that each printed page Moreover, the rotation time of the intermediate transfer member can be optimized. Therefore, the rotational speed change of the intermediate transfer member due to the machine difference, environment, and change with time can be followed, and a color toner image is obtained by transferring a plurality of toner images of different colors on the intermediate transfer member in an overlapping manner. At times, the toner images of the respective colors can be accurately polymerized, and a high-definition color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a color laser printer of the present invention.

FIG. 2 is a block diagram of a control device.

FIG. 3 is a print control time chart.

FIG. 4 is a color matching control time chart during four-color printing (continuous printing).

FIG. 5 is a color matching control time chart during four-color printing (intermittent printing).

[Explanation of symbols]

5 ... Photosensitive belt, 6 ... Photosensitive belt drive motor, 8 ... Scanning exposure device, 9-12 ... Developing device, 15 ... Intermediate transfer drum,
26 ... Control device, 27 ... Laser printer, 33 ... Detection signal processing circuit, 34 ... Clock supply circuit, 35 ... Control drive circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Nakano 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture Inside the Hiritsu Manufacturing Co., Ltd. Mechanical Research Laboratory

Claims (2)

[Claims] 1. A photoconductor that is rotated by a photoconductor drive device, and an exposure device that forms an electrostatic latent image on the surface of the photoconductor.
A developing device that forms a toner image on the electrostatic latent image, an intermediate transfer body that is rotated while being in contact with the surface of the photoconductor to transfer the toner image on the photoconductor, and a frame body that assembles them. In the color laser printer, the toner image of different colors is repeatedly formed on the photoconductor, the toner images of the respective colors are sequentially transferred to the intermediate transfer body, and a color image is formed by superposing the toner images on the intermediate transfer body. A control drive circuit that controls the rotation speed of the apparatus determines the rotation speed of the photoconductor when the electrostatic latent image of the first color is formed during printing. A color laser printer, characterized in that the rotation time of a transfer member is measured, and the speed is corrected by a time difference from the rotation reference time of the intermediate transfer member. 2. The control drive circuit according to claim 1, wherein
A color laser printer characterized in that the speed correction of the photosensitive member is performed before the formation of the electrostatic latent image of the first color of the next printing only when the non-print standby state has passed for a predetermined time or more.