JPH0243574A - Method and device for controlling rotation in multiplex transfer device - Google Patents

Abstract

PURPOSE:To prevent the dislocation of a formed image by storing the pattern of changes in the angular velocity of a transfer roll beforehand and controlling the angular velocity of the rotation of a driving motor driving the transfer roll based on the pattern of the changes. CONSTITUTION:The memory means stores beforehand the information of the changes in the angular velocity of the transfer roll 1 when the driving motor 5 driving the transfer roll 1 is rotated at a specified angle. When transfer is performed, the information of the changes in the angular velocity is read from the memory means and the angular velocity of the driving motor 5 is changed based on the information. Thus, the angular velocity of the transfer roll 1 is fixed and the dislocation of the image can be prevented when multiplex transfer is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for correcting positional deviation during transfer in an image forming apparatus that performs multiple transfer, such as a color image forming apparatus.

[Conventional technology]

For example, a color copier that uses electrophotography.

In a color image forming apparatus such as a color printer, a color image is generally obtained by sequentially multiple-transferring yellow, magenta, cyan, and black coloring materials.

One of the structures for performing this multiple transfer is to press four drum-shaped photoreceptors against a common transfer roll, form an image of each color on each photoreceptor, and then transfer the image of each color to the transfer roll. There is a known method in which images are transferred one after another onto a rolled up sheet of paper.

[Problem to be solved by the invention]

When forming a color image by overlapping and transferring the images of each color formed on multiple photoreceptors onto the paper on the transfer roll, multiple transfer is performed with the positions of the images of each color accurately aligned. There must be. For this purpose, it is necessary to maintain the angular velocity of the transfer roll axis constant.

However, eccentricity of the transfer roll, the drive gear between the drive motor and the transfer roll, the drive motor, etc.

The angular velocity of the transfer roll varies due to manufacturing errors, installation errors, and the like. For example, when transferring, Figure 6 (a)
) as shown in FIG. 1, and positional deviations having a period of one rotation of the transfer roll and positional deviations having a period shorter than this occur.

For this reason, when the images of each color formed on the photoreceptor are transferred to the paper on the transfer roll, the positions are shifted, resulting in color misregistration, which significantly reduces the quality of the output image.

Conventionally, this has been addressed by increasing the manufacturing accuracy and installation accuracy of the transfer roll and drive gear, but there is a limit to increasing the manufacturing accuracy and installation accuracy.
Further, there was a problem that it was time-consuming and costly.

The present invention was devised to solve the above-mentioned problems, and an object of the present invention is to reduce the positional deviation of images during transfer without significantly increasing the mechanical precision of the device.

[Means to solve the problem]

In order to achieve the above object, a rotation control method for a multiple transfer device according to the present invention is provided, in which a plurality of images are multiple-transferred to a common transfer roll. Storing information on a change in angular velocity of the transfer roll when rotated at an angular velocity in a storage means, reading information on a change in the angular velocity from the storage means at the time of transfer, and changing the angular velocity of the drive motor based on the information. It is characterized by

Further, the rotation control device in the multiple transfer device of the present invention includes:
In order to achieve the above object, a multiple transfer device in which multiple images are transferred onto a common transfer roll includes an angular velocity detection means for detecting the angular velocity of the transfer roll, and an angular velocity of a drive motor that drives the transfer roll. a rotation control means for controlling the transfer roller; a means for detecting a change in the angular velocity of the transfer roll when the drive motor is rotated at a constant angular velocity; a storage means for storing information on the detected change in the angular velocity; The present invention is characterized by comprising means for reading out information on changes in the angular velocity from the storage means and supplying the information to the rotation control means to change the angular velocity of the drive motor.

[Effect]

In the present invention, information on changes in the angular velocity of the transfer roll when the drive motor that drives the transfer roll is rotated at a constant angular velocity is stored in advance in the storage means. Then, during transfer, information on the change in the angular velocity is read from the storage means, and the angular velocity of the drive motor is changed based on this information. As a result, even if, for example, there is eccentricity in the drive system, the angular velocity i of the transfer roll remains constant, and positional deviation of images will not occur during multiple transfers.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 1 is an explanatory diagram schematically showing main parts of a color image forming apparatus to which a rotation control device of the present invention is applied.

In the figure, 1 indicates a transfer roll, and this transfer roll 1
A sheet of paper is wrapped around the outer periphery of the transfer roller 1 and is conveyed as the transfer roll 1 rotates. For example, on the outer periphery of the transfer roll 1,
Four photoreceptors 2a, 2b, 2c, and 2d corresponding to the colors , yellow, magenta, cyan, and black are pressed together. Each photoreceptor 2a.

2b, 2c, and 2d are each provided with an image forming section (not shown) corresponding to each color, and the transfer roll 1
Each photoreceptor 2a, 2b, 2c, 2 is rotated in synchronization with 0 rotation.
Toner images of each color are sequentially formed on d. These toner images are superimposed and transferred to the same position on the sheet of paper wound around the transfer roll 1.

A drive motor 5 is connected to the shaft 1a of the transfer roll 1 via a gear device 4 consisting of gears 4a to 4d.
As the drive motor 5 rotates, the transfer roll 1 also rotates. The number of teeth of the gears 4a to 4d is, for example, 44:264:
35:350, and the rotation of the drive motor 5 is slowed down and transmitted to the transfer roll 1. Note that in this embodiment, a stepping motor is used as the drive motor 5. In addition, the transfer roll 10 axis 1a has
A row encoder 3 is attached to detect the angular velocity of 10 rotations of the transfer roll. Then, the rotation of the drive motor 5 is controlled by a control section 6, which will be described later, so that the detected angular velocity matches a predetermined angular velocity.

FIG. 2 shows a block diagram of the control section 6. As shown in FIG.

Output S of oscillator 14. ,. is frequency-divided by, for example, an interval counter 13b such as an integrated circuit 8254 manufactured by Intel Corporation, and is supplied to the drive motor 5 as a drive pulse SDP of a predetermined frequency. This drive pulse S. , is determined by the data SPS sent from the CPU 7 to the interval counter 13b. Further, an enable signal 5IGN is supplied from the CPU 7 to the interval counter 13b via the I10 port 10, and the drive motor 5 is rotated.

Stop is controlled.

In addition, the output pulse s we from the low reencoder 3
and U zero phase pulse S. is supplied to the pulse counter 12. Note that the output pulse SRE is the low reencoder 3.
This is an output generated every time the rotary encoder 3 rotates by a predetermined angle. For example, when the row encoder 3 makes one revolution, 1024 output pulses 5IIE are generated. In addition, zero phase pulse So
is the row reencoater 3. After 1 rotation, 1 at the reference position.
This is the output that occurs twice.

The pulse counter 12 is for converting the output pulse SR1 into an interrupt signal 5IWT of a predetermined period.
As shown in the figure, it consists of two 4-pit preset counters 12a and 12b connected in series and an OR gate circuit 12C for supplying a load signal SLO to these.

The output pulse S1 from the rotary encoder 3 is sent to the pulse counter 1 based on the designation of the division number selection switch llb.
After being divided by S12.2, the interrupt signal S12. The data is supplied to the CPU 7 as a. Then, each time an interrupt signal 5INT is generated from the pulse counter 12, the oscillator 14
The CPU 7 reads the count value of the interval counter 13a driven by the output S osc of R
Store in AM 9. Note that the write/read selection switch
la is used to switch between the corrected chiffle creation mode and the actual transfer mode, which will be described later.

The above-mentioned control section 6 receives the pulse Si! generated from the low-resolution encoder 3, as will be described later. , So, etc. to calculate a correction frequency and output it to the drive motor 5.

In this embodiment, in the correction table creation mode, one cycle of the transfer roll 1 is divided into n sections, for example, 8 sections, and each section is passed when the transfer roll 1 is rotated at a standard speed. The time required to do this, that is, interval data, is stored in the RAM 9 as a table. In the transfer mode, the rotational speed of the transfer roll 1 is controlled based on the data in this table. Processing such as storage into the RAM 9 is performed by the control unit 6 described above.

In order to rotate the transfer roll 1 at a standard speed, it is necessary to drive the drive motor 5 at a standard frequency. this,
The standard frequency is the frequency for obtaining a specified constant circumferential speed, assuming that there is no eccentricity in the transfer roll 1, etc. fS = XR, XN Above, however, f5: standard frequency V: circumferential speed L; Circumference RG: Gear ratio N: Represented by the number of pulses required for one rotation of the motor.

Note that this standard frequency f is common to the same model, so it may be written in advance in FROM 8 at the time of factory shipment.

The operation of the circuit shown in FIG. 2 will be explained in detail below.

First, operate the write/read selection switch lla to
For example, a high level signal is supplied to U7 to set the correction table creation mode. Then, the CPU 7 executes FRO
Read data of standard frequency f from M8 and use this as preset data Sps in interval counter 13.
Load into b. The interval counter 13b is supplied with the output SO5° from the oscillator 14, and outputs S05° from the oscillator 14 according to the preset data SPH.
. , C, the frequency of the output SOP of the interval counter 13b is the standard frequency f,
becomes. Then, the drive motor 5 is driven to rotate based on this standard frequency fs, and is decelerated by the gear device 4 to rotate the transfer roll 1. Since the drive motor 5 is a stepping motor, the rotational angular velocity of the drive motor 5 is completely defined by the standard frequency f.

Next, the output pulse 5aE of the rotary encoder 3 (see FIG. 4(a)) generated by 10 rotations of the transfer roll is converted into a zero-phase pulse S. (see figure (b)) as a reference, the pulse counter 12 divides the frequency at a division ratio matching the control division number, and the divided pulse 5IXT (see figure (c)) is sent to the CPU 7 as an interrupt signal. Supply as.

The number of pulses generated in one revolution of the rotary encoder 3 is l,
When the number of control divisions is m, the frequency division number n is determined by n=.

For example, f=1024. When m=8, n=
128, and when 128 pulses are manually input from the low-resolution encoder 3, one pulse is output from the pulse counter 12. The number of controlled divisions of the pulse counter 12 can be changed as required by the division number selection switch llb.

That is, as shown in FIG.
When a load signal is supplied to the preset counters 12a and 12b, the initial value set by the division number selection switch llb is loaded into the preset counters 12a and 12b.

Then, each time the output pulse SR1 of the rotary encoder 3 is supplied, it counts down, and when the count value reaches 0, the pulse S! Generates a new value and reloads the initial values.

Therefore, by changing the initial value, the pulse 5INT
For example, if the initial value is made smaller, the interval between pulses 5INT becomes shorter, and the control division number m becomes thicker.

When the CPU 7 is interrupted by the first interrupt signal 5IIIT after 80 zero-phase pulses, the CPU 7 reads the count value of the interval counter 13a at this point and calculates the interval T corresponding to the first section.
It is temporarily stored in the RAM 9 as a file.

However, to simplify the explanation here, it is assumed that the interval counter 13a is reset by the zero-phase pulse S0, but in reality, it is reset by taking the difference from the count value of the interval counter 13a in the previous section. is not necessarily necessary. Then, when the interrupt signal SINA corresponding to the next section is input, it is read in the same way, and the difference between the count value and the previously read count value of the interval counter 13a is calculated.
is measured and stored in RAM 9.

The interval counter 13b receives a constant frequency output S from the oscillator 14. ,. (see FIG. 4(d)), the count value of the interval counter 13b indicates the elapsed time.

For example, if the angular velocity of the transfer roll 1 slows down in a certain section for some reason even though the angular velocity of the drive motor 5 is constant, the interval of this section becomes longer and this time information is written in the RAM 9. This operation is repeated for one period. For example, when the control division number m is set to 8, the data of intervals T1 to T8 of each section is sequentially stored in the RAM 9 every time the transfer roll 1 rotates 178 times. At this time, the zero phase pulse S0 of the low reencoder 3 is also supplied to the CPU 7; The initial value Δ1 of the address is set by the CPU 7 with reference to Δ1, and thereafter, for each section, that is,
Each time the interrupt signal SIN is input manually, the address is specified by adding a certain value.

Therefore, a correction table is created on R to M9 in the format shown in Table 1.

Operate the first table write/continuation selection switch lla to
For example, a low level signal is supplied to set the transfer mode.

When starting the transfer, the drive motor 5 is driven at the standard frequency f to rotate the transfer roll 1. Then, the zero phase pulse S of the low reencoder 3. After detecting
Based on the interval stored in the correction table and the time read for each section, according to the following formula,
The corrected frequency for the next section is calculated and output to the drive motor 5.

That is, one circumference of the transfer roll 1 is divided into eight parts of 45 degrees each,
An address (A, .about.A8) and an interval (T, .about.T,) are made to correspond to each divided section.

The above-described correction table creation work may be performed, for example, when the image forming apparatus is installed.

Next, the operation when actually performing transfer will be explained.

However, fo: correction frequency ET(K+1): (K+l) integrated value of the intervals of the correction table in section 1 [of the 1st section ΣT(K): integrated value of the intervals of the correction table up to the Kth section ΣT, d(K+ 1): The integrated value of the ideal time up to the (K+ 1)th section ET, c(K): The integrated value of the actual time up to the (K+ 1)th section For example, it is subject to correction. Interval IT(K+1)-ET(K)) of the correction table for the 5th interval
(see figure) is long, that is, when the angular velocity of the transfer roll 1 when the drive motor 5 is rotated at a constant angular velocity is slow in the 5th section, the correction frequency fh becomes high. As a result, the rotational angular velocity of the transfer roll 1 driven by the drive motor 5 is controlled to be constant, and the peripheral speed of the transfer roll 1 is constant.

In addition, if the angular velocity in the K-th section becomes slower due to changes over time or temperature, (Σrid(K+ 1) - ΣT, c(K)) becomes smaller, the correction frequency f, becomes higher and transfer The angular velocity of rotation of the roll 1 is always constant.

As described above, according to this embodiment, it is possible not only to correct changes in the angular velocity of the transfer roll 1 specific to each image forming apparatus, but also to correct dynamic changes in the angular velocity caused by changes over time, temperature changes, etc. can do.

As a result, the speed at each transfer portion of the four photoreceptors 2a, 2b, 2c, and 2d becomes constant, and positional deviation between the transfer portions can be reduced. For example, when the position error ΔX before correction is as shown in FIG. 6(a), the position error ΔX after correction becomes extremely small as shown in FIGS. Note that this position error is measured by a measuring device based on the output of the rotary encoder 3 using the method described below. That is, the output of the low reencoder 3 is F/V (frequency/voltage) converted, and then A
/D (analog/digital) conversion and store the digital value at an appropriate sampling period. Then, each stored digital value is averaged, and the difference between each digital value and the average value is determined. Since this difference is a difference in speed, it is time-integrated to obtain a position error.

Although the above embodiments have been described using a color image forming apparatus as an example, the present invention is not limited to this, and may be applied to an image forming apparatus that combines a plurality of monochromatic images to form a new image. The present invention can also be applied to.

Furthermore, in the above-described embodiment, the user operates the write/read selection switch to switch between the correction table creation mode and the transfer mode, but the present invention is not limited to this. The mode may be set to correction table creation mode, and the transfer mode may be set automatically after the correction table is created.

〔Effect of the invention〕

As described above, in the present invention, a pattern of changes in the angular velocity of the transfer roll is stored in advance, and upon transfer, the angular velocity of rotation of the drive motor that drives the transfer roll is controlled based on this pattern of changes. are doing. As a result, even though the angular velocity of the drive motor is constant,
Even if the angular velocity of the transfer roll changes for some reason, the angular velocity of the transfer roll is kept constant by correcting the angular velocity of the drive motor, and a plurality of images are transferred to the same position on the transfer roll while accurately overlapping. Therefore, no positional deviation occurs in the formed image, and a high quality output image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the main parts of a color image forming apparatus to which the rotation control device of the present invention is applied, FIG. 2 is a block diagram showing details of the control section of the color image forming apparatus, and FIG.
The figure is a block diagram showing the configuration of the pulse counter, Figure 4 is a waveform diagram to explain the operation of the control section, Figure 5 is a diagram to explain the correction operation, and Figure 6 is before and after correction. It is a graph showing the error in the position of . 1: Transfer roll 1a: Axis 2a, 2b, 2c, 2d: Photoreceptor 3: Rotor encoder 4: Gear device 4a to 4d: Gear 5: Drive motor 6: Control unit 7: CPU 8: PROM9: RA
M 10: I10 port 11; selection switch 12: pulse counter 12a, 12b nib reset counter 12C NOR gate circuit 13a, 13b: interval counter 14' oscillator Figure 2

Claims (1)

[Claims] 1. In a multiple transfer device in which a plurality of images are transferred multiple times to a common transfer roll, when a drive motor that drives the transfer roll is rotated at a constant angular velocity in advance, Rotation in a multiple transfer device, characterized in that information on changes in angular velocity is stored in a storage means, information on changes in angular velocity is read from the storage means at the time of transfer, and the angular velocity of the drive motor is changed based on the information. Control method. 2. In a multiple transfer device in which a plurality of images are multiple-transferred to a common transfer roll, angular velocity detection means detects the angular velocity of the transfer roll, and rotation control controls the angular velocity of a drive motor that drives the transfer roll. means for detecting a change in the angular velocity of the transfer roll when the drive motor is rotated at a constant angular velocity; a storage means for storing information on the detected change in angular velocity; A rotation control device for a multiple transfer device, comprising: means for reading out information on changes in the angular velocity and supplying the information to the rotation control means to change the angular velocity of the drive motor.