JP4425082B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an endless belt stretched by a driving roller and a driven roller, which carries a toner image formed of a plurality of colors of toner and transfers the toner image onto a transfer material. The present invention relates to a device and a program for controlling the device.

  Among image forming apparatuses such as digital color copying machines, there is a color image forming apparatus that uses an endless belt as an intermediate transfer belt. This type of color image forming apparatus generally includes a writing apparatus for four colors of yellow, cyan, magenta, and black, four photosensitive drums that are written by this writing apparatus to form a latent image, and on each photosensitive drum. Development apparatus for developing the latent image formed on the toner into four color toner images, an endless intermediate transfer belt on which primary development is performed in a state where the developed toner images of each color are accurately superimposed, and this intermediate transfer A transfer device is provided for transferring a full-color composite color image (toner image) formed on the belt to transfer paper.

  The intermediate transfer belt is stretched around a driving roller, a tension roller, and a driven roller, and is driven by the driving roller.

  In such a color image forming apparatus having a so-called belt driving mechanism in which an endless belt is stretched around a plurality of rollers, even if the driving roller is rotated at a constant speed, the eccentricity of the driving roller (the center of the roller shaft) The travel speed of the endless belt fluctuates with the rotation period of the drive roller due to the positional deviation from the roller rotation axis center. The same applies when the driven roller is eccentric. When the traveling speed fluctuates, in a multi-color image forming apparatus, color misregistration, color unevenness, etc. occur due to relative misregistration between the colors, and a high-quality image cannot be obtained.

In view of this, in the conventional apparatus, the intermediate transfer belt is bridged between a driving roller and a driven roller having different outer diameters , and an endless belt is driven by rotation of the driving roller to form an image. While the drive roller is driven to rotate at a low speed, the angular velocity information detected by the detection means is acquired for at least one cycle of the drive roller, and the speed detection error due to the eccentricity of the drive roller in the acquired angular velocity information. By canceling the components, the speed detection error component due to the eccentricity of the driven roller is extracted, and at the time of image formation, the angular speed information detected by the angular speed detection means and the speed detection error component extracted by the speed detection error component extraction means Control means for controlling the running speed of the endless belt based on the difference data.

  With this configuration, when the driving roller is rotationally driven at a constant speed, angular velocity information detected by the angular velocity detecting means is acquired over at least one cycle of the driving roller. At this time, the speed fluctuation component due to the eccentricity of the driving roller repeats the same change in the rotation cycle of the driving roller. For example, when the angular velocity information for one cycle of the driving roller is acquired, the angular velocity information is driven. The speed fluctuation component due to the eccentricity of the drive roller can be canceled by dividing the roller by a half cycle and adding the first half and the second half.

Using this principle, the extraction means cancels out the speed fluctuation component due to the eccentricity of the driving roller in the angular velocity information detected by the detection means, thereby extracting the speed detection error component due to the eccentricity of the driven roller. At the time of image formation, the difference between the angular velocity information detected by the detecting means and the speed detection error component extracted by the extracting means is taken. The difference data obtained at this time is the data obtained by removing the speed detection error component due to the eccentricity of the driven roller from the angular velocity information of the driven roller, that is, the data matching the running speed of the endless belt. By controlling the running speed of the endless belt based on the above, the running speed of the endless belt can be made constant (see Patent Document 1).
In another conventional apparatus, an endless conveyance belt is bridged between a driving roller and a driven roller, and an image is formed by running the conveyance belt by rotation of the driving roller. Speed setting means is provided to cancel the load fluctuation of the conveyor belt due to variations (see Patent Document 2).
JP 2000-47547 A JP 2001-350387 A

The fluctuation of the running speed of the endless belt includes a sudden short-time fluctuation due to disturbance in addition to the speed fluctuation based on the eccentricity of the driving roller and the driven roller. In the image forming apparatus described in Patent Document 1,
Since the difference between the angular velocity information by the speed detection means and the speed detection error component by the extraction means is taken at the time of image formation, it can cope with the slow speed fluctuation caused by the thermal expansion of the driving roller and the driven roller due to the environmental change, but disturbance etc. Therefore, it is impossible to cope with a short-time speed fluctuation that occurs randomly. Further, the image forming apparatus described in Patent Document 2 is directed to correcting the transfer position deviation due to the eccentricity of the photosensitive drum, and does not deal with the short-time speed fluctuation.

Therefore, according to the present invention, when an image is formed using an endless intermediate transfer belt, a constant belt speed is secured against slow speed fluctuations such as eccentricity of a driving roller and a driven roller and a change in belt thickness caused by thermal expansion. as well as, the purpose that driving the belt at a constant speed relative to the sudden speed fluctuation caused by disturbance or the like.

The invention according to claim 1 is an endless belt stretched by a driving roller and a driven roller, and includes an endless belt that carries a toner image formed of a plurality of colors of toner and transfers the toner image onto a transfer material. In the image forming apparatus, a plurality of detected objects and non-detected objects provided at substantially equal intervals on the peripheral surface of the driven roller, a means for detecting the detected object, and a rise of a pulse signal generated when the detected object is detected Counting means for counting the number of clock pulses from falling or falling to rising, speed calculating means for calculating the moving speed of the driven roller from the count value of the number of clock pulses by the counting means, and the moving speed of the driven roller A means for storing a target speed, and a correction for calculating a speed correction amount so that the driven roller becomes a constant speed from the calculated moving speed and the target speed. And amount calculating means, based on the speed correction amount, an image forming apparatus characterized by comprising a motor driving means for driving the motor.
A second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the driving roller has an outer periphery that is an integral multiple of the outer periphery of the driven roller .
Invention 請 Motomeko 3 is a endless belt that is stretched by a driving roller and a driven roller, carrying the toner images formed by the plurality of colors of toner, an endless belt for transferring a transfer material the toner image Count the number of clock pulses between the rising edge and falling edge of the pulse signal generated by the detection of multiple detection objects provided at substantially equal intervals on the peripheral surface of the driven roller. Counting means, speed calculating means for calculating the moving speed of the driven roller from a count value of the number of clock pulses by the counting means, means for storing a target speed of the moving speed of the driven roller, and the calculated moving speed A correction amount calculating means for obtaining a speed correction amount from the moving speed of the driven roller so that the driven roller becomes a constant speed; Motor driving means for driving the can motor is a program for functioning as a.

  According to the present invention, the constant speed of the belt is secured against slow speed fluctuations such as the eccentricity of the driving roller and the driven roller, the belt thickness change caused by thermal expansion, and the rapid speed fluctuations caused by disturbances and the like. The belt can be run at a constant speed. Therefore, in the formation of a multi-color image, there is no occurrence of color misregistration or color unevenness due to relative misregistration between colors, and a high-quality image can be obtained.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic sectional view of a color image forming apparatus in which the present invention is implemented. In FIG. 1, an image forming apparatus includes four photosensitive drums 10Y, 10C, 10M, and 10K that are four image carriers for each color of yellow, cyan, magenta, and black, and a charging device (not configured) around the photosensitive drum 10. The exposure device 7 irradiates light corresponding to each color of yellow, cyan, magenta, and black to the charged surface of the photosensitive drum 10 charged by the charging device, and forms a latent image thereon, and the latent image. Development units 11Y, 11C, 11M, and 11K that respectively develop toner images of different colors, a primary transfer roller 13 that constitutes a primary transfer device of the toner image, a cleaning unit (not shown), and the like are provided. . Further, an intermediate transfer belt 12 on which toner images of different colors are primarily transferred in a superimposed state is provided. In this embodiment, a photosensitive drum 10, a charging device (not shown), a developing unit 11, a cleaning unit (not shown), and the like are arranged on the lower side of the intermediate transfer belt 12 along the rotation direction (the direction of arrow A). Established. A primary transfer roller 13 is disposed opposite to each photosensitive drum 10, and rotates with the intermediate transfer belt 12 sandwiched between each primary transfer roller 13 and the photosensitive drum 10. ing.

  The intermediate transfer belt 12 is an endless belt, and the intermediate transfer belt 12 is stretched around a driving roller 14, a tension roller 15, and a driven roller 16 that serve as support rollers, and the driving roller 14 receives a reduction gear 5 from the driving motor 4. And is rotated in the direction of arrow A. A secondary transfer roller 17 is disposed at a position facing the driving roller 14 with the intermediate transfer belt 12 interposed therebetween.

  In the image forming apparatus, when the printing operation is started, each photosensitive drum 10 starts to rotate in the clockwise direction in FIG. 1, and the surface thereof is uniformly charged by the charging device. Light corresponding to each color image of yellow, cyan, magenta, and black is irradiated from the exposure device 7, and a latent image is formed there. Each latent image is developed by each developing unit 11 and becomes a toner image of each color of yellow, cyan, magenta, and black. The toner images of the respective colors are accurately transferred to the intermediate transfer belt 12 rotating in the direction of arrow A by the primary transfer rollers 13 so as to be superimposed on the intermediate transfer belt 12. A color image (toner image) is formed.

On the other hand, a transfer sheet P, which is a recording medium, is fed at a predetermined timing from a sheet feeding unit 6 disposed below the photosensitive drum 10, and it is interposed between the drive roller 14 and the secondary transfer roller 17. When fed, the composite color image carried on the intermediate transfer belt 12 is secondarily transferred onto the transfer paper P by the secondary transfer roller 17 at once. Then, the toner image on the transfer paper P is fixed by the fixing unit 8 and discharged onto a paper discharge tray (not shown).

  An optical sensor 18 is disposed at a certain distance on the driven roller 16 that is driven to rotate along with the surface of the intermediate transfer belt 12, and a plurality of detected objects are provided around the driven roller 16. Measurement light is emitted to the (detection mark), the reflected / transmitted light is received, and a pulsed detection signal is output. Then, the time of the change point from the change point of the pulse signal is measured, and the angular speed of the driven roller 16, that is, the conveyance speed of the intermediate transfer belt 12, is detected from that time, and the conveyance speed of the intermediate transfer belt 12 is kept constant. The control apparatus 3 which functions as a conveyance speed control means for controlling the above is provided.

  The optical sensor 18 is disposed on the driven roller 16 closer to the driving roller 14 that determines the conveyance speed of the intermediate transfer belt 12, and is caused by a conveyance speed closer to the actual speed, particularly due to a thickness deviation of the intermediate transfer belt 12. Changes in the conveyance speed are detected. The outer periphery of the driving roller 14 is an integral multiple of the outer periphery of the driven roller 16 or an integral multiple of the ratio of the outer periphery. In the present embodiment, the outer periphery of the driving roller 14: the outer periphery of the driven roller 16 = 2: 1. The driven roller 16 is provided with the detected objects 19 on the circumference thereof at approximately equal intervals over one period. Further, since the distance between the outer periphery of the driving roller 14 and the primary transfer contact of the photosensitive drum 10 in the developing unit 11 of each color is the same distance, the eccentricity of the driving roller 14 superimposes each color of the intermediate transfer belt 12. It has a mechanical structure that sometimes does not cause color misregistration.

FIG. 2 is a diagram schematically showing the configuration of the optical sensor.
FIG. 2A is an example having a cored bar portion of the driven roller 16 as the detection object 19 and a black-printed part on the surface of the cored bar as the non-detection object 20, and a reflective sensor as the optical sensor 18. Used. The detected object 19 and the non-detected object 20 are provided at substantially equal intervals and the same length in the circumference of the driven roller 16, and there are a total of four changes in one turn at the boundary of the change in the reflection type sensor. The conveyance speed of the intermediate transfer belt 12 is controlled. Here, a total of four is used, but it may be made finer as long as the cost and the performance of the control device 1 allow, and finer control is performed by making it finer, and the accuracy of the conveyance speed control is further improved.
FIG. 2B is an example having a cored bar portion of the driven roller 16 as a detected object and a notch portion of the cored bar as a non-detected object 20, and a reflective sensor 18 is used as the optical sensor 18. FIG. 2C is a reverse of FIG. 2B and uses a transmissive sensor as the optical sensor 18.

  In this way, the detected object 19 and the non-detected object 20 are approximately equally spaced (in order to obtain the angular velocity of the driven roller 16, it is not necessary to have a uniform equal distance by the arithmetic processing described later, so it may be equally spaced to some extent) Thus, unlike the rotary encoder, it is not necessary to precisely provide the slits at uniform and uniform intervals, and can be easily configured at low cost. In addition, the transmission sensor can reduce the slit width because of its structure, so that the detection accuracy is improved, but there is a disadvantage that the apparatus becomes larger.

FIG. 3 is a block diagram showing one configuration of the control device 3.
In FIG. 3, the control device 3 generates a pulse signal of 2 pulses in FIG. 2 every time the driven roller 16 makes one rotation, and generates a movement time from the rising to falling and from the falling to rising from the clock 31. A counter unit 30 for counting by clock pulses is provided. Rising from the rise, or may be counted travel time between the rising on falling from falling, in order to perform a finer control with less detection object is thus inexpensive configured who counts both changed There are advantages you can do. The clock 31 generates a periodic clock pulse at a constant time interval at a high frequency of, for example, several hundred KHz to several MHz, and is composed of a crystal oscillator or the like. Then, together with the RAM 33 that stores the count value of the moving time, the moving speed (angular speed) is obtained from the count value for the driven roller 16.1 period or the driving roller 14.1 period, and the difference from the target speed is obtained to be constant. A calculation unit 32 that obtains a speed correction amount to be a speed and a motor drive unit 34 that outputs a motor drive clock changed from the current speed to the motor driver 35 based on the speed correction amount are provided.

FIG. 4 is a timing chart showing one operation of the counter unit 30.
In FIG. 4, when the counting is started at the rising edge of the detection signal from the optical sensor 18 from the counter unit 30, the count value is successively counted up, for example, at the rising edge of the count clock from the clock 31. Then, when a change point of the next detection signal, that is, a fall occurs in the figure, the count value at that time (E000h in FIG. 4) is transferred to the register of the calculation unit 32 and at the same time, the count value is cleared. An interrupt is generated for. Then, the next count is started. The arithmetic unit 32 reads the count value from the register as appropriate using the interrupt as a trigger, and performs predetermined arithmetic processing described later. The count value between the change points of the detection signal changes according to the angular velocity of the driven roller 16. Specifically, the counter value decreases as the angular velocity of the driven roller 16 increases, and conversely increases as the angular speed decreases.

  FIG. 5 is an explanatory diagram showing one operation of the calculation unit 32. Assuming that the pulse having a detection signal output from the optical sensor 18 is n-th, first, the count value stored in the RAM 33 is included in the currently obtained count value of the movement time of ¼ rotation of the driven roller 16. The count values for the past eight times are added, the moving speed (angular speed) is obtained from the added value, the difference from the target speed is obtained, and the speed correction amount is set so as to be a constant speed, and the speed control is performed. Next, the same operation is performed for the (n + 1) th and sequentially performed as n + 2, n + 3. Thus, by obtaining the speed correction amount from one rotation period of the driving roller 14, not only the driving roller 14 but also the eccentricity of each period of the driven roller 16 can be canceled simultaneously, and control is performed for each pulse. Therefore, control can be performed in a fine time. When the outer periphery of the driving roller 14 is an integral multiple of the ratio of the outer periphery of the driven roller 16, for example, the peripheral length of the driving roller 14: the peripheral length of the driven roller 16 = 3: 2, the driven roller 16 that is the common multiple is moved six times. After obtaining the time, the same control as described above is performed.

  FIG. 6 is a waveform diagram showing speed fluctuation due to eccentricity of each roller. In general, the eccentric motion of a roller changes as shown in the figure according to its period. In this state, the speed fluctuation is detected as a detection error. For this reason, by obtaining the movement time based on the movement time for each rotation, that is, the count value for each rotation, it is possible to remove the detection error due to the speed fluctuation. Therefore, as shown in the figure, the outer circumference of the driving roller 14 is an integral multiple of the outer circumference of the driven roller 16 (the figure shows a case of twice), and at least every rotation of the driving roller 14 (every rotation in the figure) If the count value of the moving time is counted, a detection error caused by eccentricity of not only the driving roller 14 but also the driven roller 16 can be canceled. Even when the outer circumference of the driving roller 14 is set to an integral multiple of the ratio of the outer circumference of the driven roller 16, the detection error can be canceled by the same method. By doing so, thermal expansion of the drive roller 14 due to environmental changes (the drive roller 14 is a cored iron rubber roller from the viewpoint of transferability and gripping properties, and the drive roller 14 is close to the fixing unit 8. Also, since the rubber roller diameter expands due to a temperature rise and the conveyance speed of the intermediate transfer belt 12 gradually increases), it is possible to cope with a slow change in which the speed fluctuates.

FIG. 7 is a flowchart showing one control method in the calculation unit 32 of the present invention.
The procedure of the control operation will be described with reference to FIG. First, in S10, when the drive motor 4 starts to be started in a printing operation or the like and the drive motor 4 is stabilized at a steady speed, the count value by the count clock of the clock 31 in the previous stage of the counter unit 30 is cleared to zero in S11. The count start is set to ON together with the interrupt permission from the counter unit 30. Next, in S12, it is determined whether or not the speed control of the intermediate transfer belt 12 is to be executed. If it is determined to be executed, the process proceeds to S13 to determine whether it is the first step immediately after the drive motor 4 is started up. Since the count value in the first interrupt is not an accurate value because the count operation ON and the change in the detection signal are not synchronized, the control in the first interrupt is ignored in S14. In S15, the interrupt count is set to n = 0. In S16, an interrupt from the count unit 30 is waited. When an interrupt occurs, the process proceeds to S17, and the interrupt count is incremented to n = n + 1. Then, in S18, the counter value in the n-th transferred from the counter 30 to the register: with leading TC _n, memory the value to RAM 33. Next, the process returns to S16 and repeats S16 to S18 until n ≧ 8 from the beginning in S19.

When n = 8, the process proceeds to S20, and the angular velocity of the driven roller 16: V _n [mm / s] is calculated. One method of calculation is as follows . Here, when the count value of the 1/4 rotation of the driven roller 16 and TC _n, 1 cycle of the count value of the driving roller 14: As Tc _n, the count value of the past eight times including the count value currently determined It added to determine the Tc _{n.
Tc n = TC n-7 +} TC n-6 + TC n-5 + TC n-4 + TC n-3 + TC n-2
+ TC _n-1
+ TC _n

When the count clock minimum count time (sampling time) and Delta] t [ms], the count time at Tc _n: T _n [ms] is determined from the _{T n [ms] = Tc n} × Δt.

When the diameter + intermediate transfer belt thick of the driven roller 16 and r [mm], the angular velocity of the driven roller _{16: Vp n [mm / s} ] _{is, Vp n [mm / s]} = r × π × 2 / T n It is calculated from × 1000.

Next, in S21, error count due to noise or the like is eliminated. In the case of an error count, the process is repeated from S15. Here, the determination is made within a range of ± 0.5% with the target speed Vs [mm / s]. Proceeds to S22 in the case of the above range, the operation speed (speed correction _amount) to calculate the Vm n [mm / s]. One method of calculation is as follows . First, the target speed: difference between Vs [mm / s] _(deviation): Request Ve n [mm / s] as _{Ve n [mm / s] =} Vs-Vp n.

On the other hand, the integrated velocity for the difference value _Vei n [mm / s],
_{Vei n [mm / s] =} Ve n + Ve n-1, obtained as.
In this _case, Ve _n, Vei n is memory to RAM33.
From the above, the operating _speed: Vm n [mm / s] is,
_{Vm n [mm / s] =} Kp × Ve n + Ki × Vei n + Kd × (Ve n -Ve n-1) + Vs
However, it is obtained from Kp: proportional coefficient, Ki: integral coefficient, Kd: differential coefficient. This is called PID control, and can be controlled at fine intervals for each pulse change. Therefore, the speed change due to the thickness deviation of the intermediate transfer belt 12 and the transfer paper P when passing through the drive roller 14 of the transfer paper P can be controlled. This is effective when affected by short-term fluctuations due to disturbances such as speed changes due to behavior. If it is determined that the influence of short-term fluctuation due to disturbance or the like is small, the differential term multiplied by the differential coefficient Kd may be eliminated to perform PI control.

The basic seeking operation speed in S22, the target speed: difference between Vs [mm / _s]: the Ve n [mm / s] = Vs-V n, by multiplying the correction coefficient K to, [Delta] V [ it is to obtain as mm / s] = K × Ve n.

  Next, in accordance with the speed correction amount obtained in S22, a command is issued to the motor drive unit 34 to output the motor drive clock changed from the current speed to the motor drive unit 34 in S23, and intermediate transfer is performed. The speed control of the belt 12 is performed. In S25, it is determined whether the printing operation or the like is completed, and if it is determined that the drive motor 4 is stopped, the process proceeds to S26, where the drive motor 4 is lowered, and the process ends.

  In order to execute the speed control operation of the intermediate transfer belt described above, the operation procedure is described as a computer program in a general-purpose program language, and this program is recorded on an arbitrary recording medium such as a flexible disk or a CD-ROM. Then, the speed control according to the present invention can be easily performed by causing the computer of the image forming apparatus to read it.

  As described above, the image forming apparatus according to the present invention is useful in a multicolor image forming apparatus, and is particularly suitable for use in a color image forming apparatus directed to high image quality.

1 is a schematic cross-sectional configuration diagram of a color image forming apparatus in which the present invention is implemented. It is a figure which shows the structure of an optical sensor typically. It is a block diagram which shows one structure of a control apparatus. It is a timing chart which shows one operation | movement of a counter part. It is explanatory drawing which shows 1 operation | movement of a calculating part. It is a wave form diagram which shows the speed fluctuation | variation by eccentricity of a drive roller and a driven roller. It is a flowchart which shows one control method in a calculating part.

Explanation of symbols

  10 .... photosensitive drum, 11 .... developing unit, 12 .... intermediate transfer belt, 13 .... primary transfer roller, 14 .... driving roller, 15 .... tension roller, 16 .... secondary roller, ...... secondary roller Transfer roller, 18 ... Optical sensor, 19 ... Core metal part of driven roller, 20 ... Object to be detected (position mark)

Claims (3)

In an image forming apparatus provided with an endless belt stretched by a driving roller and a driven roller, which carries a toner image formed of a plurality of colors of toner and transfers the toner image to a transfer material.
A plurality of detected objects and non-detected objects provided at substantially equal intervals on the peripheral surface of the driven roller;
Means for detecting the detected object;
Count means for counting the number of clock pulses between the rising edge and the falling edge of the pulse signal generated along with the detection of the detected object, or between the falling edge and the rising edge;
Speed calculating means for calculating the moving speed of the driven roller from the count value of the number of clock pulses by the counting means;
Means for storing a target speed of the driven speed of the driven roller;
A correction amount calculating means for obtaining a speed correction amount so that the driven roller becomes a constant speed from the calculated moving speed and the target speed;
An image forming apparatus comprising: motor driving means for driving a motor based on the speed correction amount. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the driving roller has an outer periphery that is an integral multiple of the outer periphery of the driven roller. A computer of an image forming apparatus comprising an endless belt stretched by a driving roller and a driven roller, which carries a toner image formed of a plurality of colors of toner and transfers the toner image onto a transfer material. ,
A counting means for counting the number of clock pulses between the rising edge and the falling edge of the pulse signal generated along with the detection of a plurality of detection objects provided at substantially equal intervals on the peripheral surface of the driven roller;
Speed calculating means for calculating the moving speed of the driven roller from the count value of the number of clock pulses by the counting means;
Means for storing a target speed of the driven speed of the driven roller;
A correction amount calculating means for obtaining a speed correction amount so that the driven roller becomes a constant speed from the calculated moving speed and the moving speed of the driven roller;
Motor driving means for driving the motor based on the speed correction amount;
Program to function as.

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