JP2005350195A - Endless movable member carrying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably conduct control to a drive means by continuously outputting signals or data for drive control even when disconnection occurs in detection signals in position marking parts formed along the whole circumference of an endless movable member due to seams, unevenness, flaw, contamination, or attached dust in the position marking parts. <P>SOLUTION: Complementary processing parts to output high resolution signals of a shorter cyclic period than that of the detection signals for marks are provided to respective outputs from mark sensors 15a and 15b. The complementary processing parts complements the interval cycle of marks signals to achieve the function of increasing the resolution, and it increases the resolution in a false way. For the signals with increased resolution by complementation, phase difference over the cyclic period of the complementary signals is not generated even when there is position difference between the two sensors. Even when two sensor signals are switched, measurement position precision can be secured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an endless moving member conveying apparatus and an image forming apparatus that control a moving speed of an endless moving member by a drive source using a measurement result of a sensor.

In general, in an image forming apparatus having an endless moving member for image formation such as a photosensitive belt, an intermediate transfer belt, etc., the positioning of the image on the transfer material conveyed by the endless moving member or the endless moving member is highly accurate. Therefore, it is required that the moving amount and moving position of the endless moving member be accurately controlled.
However, if the moving speed of the endless moving member fluctuates for some reason, the moving amount and moving position of the endless moving member also fluctuate. For this reason, it is generally a big problem to control the endless moving member and the position of the image on the transfer material conveyed by the endless moving member with high accuracy.

For this reason, in order to control the position of the image due to the movement speed fluctuation of the endless moving member with high accuracy, the rotating shaft of the driving roller that conveys the endless belt-like moving member such as a transfer belt or a paper conveying belt, Conventionally, a rotary encoder is directly connected to a rotating shaft of a cylindrical member such as a drum, and based on the rotational angular velocity of the rotating body detected by the encoder, the rotational angular velocity of a drive motor that is a driving source of the rotating body is controlled. The image forming apparatus is used.
This control method indirectly controls the movement amount (movement position) of the endless moving member by controlling the rotational angular velocity of the rotating body.

In Patent Document 1 and Patent Document 2, a mark is formed on the belt surface, and the belt moving speed is calculated from a pulse interval obtained by detecting the mark with an optical sensor and fed back to the control. An example of how to do this is shown.
According to this method, since the behavior of the belt surface can be directly observed, the amount of belt movement can be directly used for control.

Patent Document 3 previously filed by the present applicant is provided with pattern detection means that can simultaneously read a plurality of optical patterns arranged at equal intervals on the surface of the image carrier, and the polygon mirror of the exposure device. The rotational drive of the polygon mirror is controlled by comparing the position signal and the signal of the pattern detection means.
JP-A-6-263281 JP-A-9-114348 JP 2002-251049 A

  However, as in Patent Documents 1 and 2 described above, when a mark is formed on the belt surface and the mark is detected to control the moving speed of the belt, the marks at regular intervals are determined depending on the flexibility and circumferential deviation of the belt There is a problem that it is very difficult to process the entire circumference without any breaks.

For example, when considering forming the belt by forming irregularities on the mold when forming the belt, generally heat is uniformly distributed in the annealing process after taking out from the mold to control the circumference of the belt. Since the shrinkage rate is not uniform as a whole due to not being given or the internal strain of the belt after molding, the resulting marks often do not have a constant interval.
Also, when considering a method by printing or adhesion, if the belt circumferential tolerance is 0.2 to 0.3%, a belt having a circumferential length of 500 mm has a deviation of 1 mm or more, and a mark can be formed without a break. It turns out to be very difficult.

  Here, the above-mentioned one in Patent Document 1 is suitable for reducing the color shift by storing the speed fluctuation of one rotation in a memory and reproducing the speed fluctuation in the next round. It does not take into account the countermeasures for mark seams in detecting marks formed over the entire circumference at intervals.

  Patent Document 2 is effective for a continuous signal output such as a rotary encoder. However, when a mark is formed on the belt surface, if there is a mark break, an error occurs in speed measurement at that portion. Occurs, and the operation becomes unstable. In other words, it does not take into account measures for mark seams in detection of marks formed over the entire circumference of the belt.

  Further, the above-mentioned Patent Document 3 is affected by non-uniform mark signals, dirt, scratches, and attached dust by comparing the position signal of the polygon mirror with the result of reading a plurality of optical patterns. It is suitable to control the driving of the polygon mirror without any problems. However, the detection signal of the position indication part of the endless belt can be used as a countermeasure against the seam of the position indication part with a high resolution signal having a cycle shorter than the cycle. It is not taken into consideration to control the drive motor that moves the endless belt.

  The present invention has been made in view of such a situation, and the detection signal of the position indicator formed over the entire circumference of the moving part is caused by the joint of the position indicator, unevenness, scratches, dirt, adhered dust, etc. To provide an endless moving member conveying apparatus and an image forming apparatus capable of stably controlling a driving unit by allowing a signal or data for driving control to be output without interruption even when the interruption occurs. With the goal.

  In order to achieve this object, an endless moving member conveying apparatus as a first aspect of the present invention is an endless moving member conveying apparatus that moves (rotates, conveys, etc.) an endless moving member by power from a driving means. A position indicator (mark, hole, etc.) is arranged over the entire circumference at substantially constant intervals in the moving direction of the moving part, and when the moving part moves, it detects that the position indicator passes and outputs a signal. Two or more sensor means (mark sensors, etc.) are arranged to detect the position indicator at different positions in the moving direction of the moving part, and from the period of the detection signal of the position indicator outputted from the sensor means Further, the present invention is characterized by comprising an interpolation processing means for outputting a high-resolution signal with a short cycle and a control means for controlling the driving means based on the output from the interpolation processing means.

  The above-described interpolation processing means includes a signal period calculation section that samples the detection signal of the position indicator from the sensor means and calculates the period of the detection signal, and the signal period calculated by the signal period calculation section is divided into n It is preferable to include a divided signal generation unit that generates a periodic signal.

  The interpolation processing unit generates a high-resolution signal having a cycle shorter than the cycle of the detection signal of the position indicator output from the sensor unit, using a clock signal having a fixed cycle interval that is reset by a signal edge of the detection signal. It may be.

  The interpolation processing means described above may be configured by a computer that performs processing based on a program.

  The sensor means described above is an analog output type that outputs a sinusoidal wave depending on the presence or absence of a detection signal of the position indicator, and the interpolation processing means described above applies a pulse for each equal phase from the analog output of the sensor means according to the signal amplitude value. A multiplication circuit that generates and increases the resolution may be provided.

  The interpolation processing means described above preferably generates and outputs an interpolation signal similar to a state in which there is no signal failure when the detection signal from the sensor means is defective.

  The apparatus further comprises a seam sensor means for detecting a seam of the position indicating portion disposed in the moving part, and based on a detection result by the seam sensor means, measures a position that is not a seam from output signals from two or more sensor means. The signal from the sensor means is preferably selected.

  It is preferable that a phase comparison circuit for comparing the phases of output signals from the two or more sensor means described above is provided, and the control means described above further controls the drive means using the output from the phase comparison circuit.

  It is preferable that the above-described two or more sensor means are attached so that a gap wider than the width of the seam generated when the position indicator is formed on the entire circumference of the moving part.

The resolution improved by the above-described interpolation processing means is preferably higher than the required accuracy for positioning the endless moving member.
The moving part is preferably a drum-shaped member.

  The moving part described above is the front or back surface of the endless moving member, the endless moving member is an endless belt, and the endless moving member conveying device includes a plurality of rollers including a driving roller that rotates by obtaining driving torque from the driving means. And an endless belt that is stretched around a plurality of rollers.

  The endless moving member conveying device described above is a belt conveying device including a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a driving unit, and an endless moving member that is stretched over the plurality of rollers. The moved portion may be any of the rollers that stretch the endless moving member.

  The endless moving member conveying device described above is a belt conveying device including a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a driving unit, and an endless moving member that is stretched over the plurality of rollers. The moving part may be a rotary encoder that is linked to the driving means.

  An image forming apparatus according to a second aspect of the present invention includes an endless moving member conveying apparatus according to the first aspect of the present invention, and an electronic process unit using an electrophotographic method for forming an image of each color on a sheet. The moving portion described above is a photosensitive belt in an electronic process section.

  An endless moving member conveyance device as a first aspect of the present invention and an electronic process unit for forming an image on a sheet, and the moving part described above is a transfer for transferring an image of the electronic process unit to a sheet It may be a belt or an intermediate transfer belt.

  An endless moving member conveying device as a first aspect of the present invention and an inkjet image forming unit that forms an image on a sheet by an inkjet method, and the moving part described above may be a paper conveying roller or a paper conveying belt Good.

  As described above, according to the present invention, the detection signal of the position indicator formed over the entire circumference of the endless moving member is interrupted by the seam of the position indicator, unevenness, scratches, dirt, attached dust, etc. However, since the signal or data for drive control can be output without interruption, the drive means can be controlled stably.

Next, an embodiment in which the endless moving member conveying apparatus and the image forming apparatus according to the present invention are applied to a tandem type color image forming apparatus will be described in detail with reference to the drawings.
The color image forming apparatus of the present embodiment exemplifies a suitable one that can perform stable drive control by obtaining a continuous signal without a break even if there is a seam in the belt mark.

  An example of a color image forming apparatus as a preferred embodiment of the present invention will be described with reference to FIG. This color image forming apparatus forms toner images of respective colors on a sheet 2 in order from the upstream side toward the moving direction (conveying direction) of the conveying belt along a conveying belt 3 that conveys a transfer sheet 2 as a recording medium. This is a so-called tandem type in which electronic process units 1K, 1M, 1Y, and 1C are provided. These electronic process units 1 function as an image forming unit.

  The electronic process unit 1K forms a black image, the electronic process unit 1M forms a magenta, the electronic process unit 1C forms a cyan image, and the electronic process unit 1Y forms a yellow image. The internal configuration is the same for each electronic process unit. Therefore, in the following description, the electronic process unit 1K will be described in detail. However, for other electronic process units, symbols such as M, Y, and C are used instead of K of the components related to the electronic process unit 1K. It is only displayed in the figure with the attached ones.

  The conveyor belt 3 is composed of a driving roller, one of which is driven to rotate, and an endless belt that is rotatably supported by the conveying rollers 4, 5 that are driven rollers that are driven to rotate on the other side. , Can be rotated in the direction of the arrow. A paper feed tray 6 in which the paper 2 is stored is provided below the transport belt 3. Of the sheets 2 stored in the sheet feeding tray 6, the sheet 2 at the uppermost position is sent out at the time of image formation and is attracted to the transport belt 3 by electrostatic attraction. The sheet 2 thus sucked on the conveyor belt 3 is conveyed to the first electronic process section 1K, where a black image is transferred.

  The electronic process unit 1K includes a photoconductor drum 7K as an image carrier, and a charger 8K, an exposure device 9K, a developing device 10K, a photoconductor cleaner 11K, and the like disposed around the photoconductor drum 7K. . As the exposure device 9K, a laser scanner is used, and laser light from a laser light source is reflected by a polygon mirror and emitted as exposure light through an optical system using an fθ lens, a deflection mirror, and the like.

  At the time of image formation, the peripheral surface of the photosensitive drum 7K is uniformly charged by the charger 8K in the dark, and then exposed by exposure light 12K corresponding to the black image from the exposure device 8Y, in this example, by laser light. An electrostatic latent image is formed. The electrostatic latent image is visualized with black toner in the developing device 10K, and a black toner image is formed on the photosensitive drum 7K.

  This toner image is transferred onto the sheet 2 by the action of the transfer device 13K at a position where the photosensitive drum 7K and the sheet 2 on the conveyance belt 3 are in contact, that is, a so-called transfer position, and a monochrome (black) image is formed on the sheet 2. It is formed. After the transfer, the photosensitive drum 7K has unnecessary toner remaining on the peripheral surface of the photosensitive drum 7K removed by the photosensitive cleaner 11K, and is ready for the next image formation.

  In this way, the sheet 2 on which the single color (black) is transferred by the electronic process unit 1K is transported to the next electronic process unit 1M by the transport belt 3. In the electronic process unit 1M, the magenta toner image formed on the photosensitive drum 7M by the same process as in the electronic process unit 1K described above is superimposed and transferred onto the black toner image on the paper 2.

The paper 2 is further transported to the next electronic process unit 1Y, and the yellow toner image formed on the photosensitive drum 7Y is similarly transferred to the black and magenta toner images already formed on the paper 2. The Similarly, in the next electronic process unit 1C, a cyan toner image is transferred and overlapped to obtain a full color image.
The sheet 2 on which the full-color superimposed image is thus formed passes through the electronic process unit 1C, is peeled off from the conveying belt 3 and fixed by the fixing unit 14, and is then discharged.

  In the color image forming apparatus configured as described above, the error in the distance between the photosensitive drum axes, the parallelism error in the photosensitive drum, the installation error in the deflection mirror, the writing timing error of the exposure light on the photosensitive drum, the linear velocity of the photosensitive drum. Due to fluctuations and the like, there is a possibility that an image does not overlap at a position that should originally overlap, and a problem arises that a positional shift occurs between colors.

  Such inter-color misregistration components mainly include skew (diagonal misalignment) due to uneven inclinations of the scanning lines of the respective colors, and sub scanning directions (conveying direction of the sheet 2 by the conveying belt 3) orthogonal to the main scanning direction. There are sub-scanning registration shifts in which the image position is shifted, sub-scanning pitch unevenness, writing positions in the main scanning direction, or magnification shifts in which the scanning line length is different between main scanning registration shift colors in which the writing end position is shifted.

The present embodiment provides a belt conveying apparatus that can reduce unevenness in the speed of the conveying belt that causes the above-described sub-scanning registration deviation.
As described in the prior art, the positioning error due to the speed fluctuation of the belt conveying device used in the image forming apparatus as shown in FIG. 1 is caused by the fluctuation of the thickness of the conveying belt 3, the eccentricity of the roller, the drive motor (driving means). Due to the speed variation, a waveform having a plurality of frequency components as shown in FIG. 2 is obtained. In an output image obtained by superimposing images formed during position fluctuation, an image in which the positions of the respective colors are not aligned may be output, which causes image quality deterioration such as color shift or color change.

  A mark is formed on the conveyor belt as in the prior art, and the mark is read by an optical sensor as shown in FIG. 3, for example, and the speed is calculated from the time interval of the signal to control the drive motor. However, it is possible to reduce the speed unevenness and positioning error of the conveyor belt as described above. However, when the mark is actually formed on the conveyor belt, the leading end and the end of the mark are aligned as described in the related art. As shown in FIG. 4, generally, a seam is formed in the mark.

For this reason, in the conventional belt conveying apparatus described above, a discontinuous portion of the signal is generated by the joint portion of the mark, and for example, when speed control is performed by a PLL which is a general motor control algorithm, it is shown in FIG. As described above, the phase difference between the reference clock and the sensor signal greatly fluctuates due to the discontinuous portion (marker discontinuous portion) of the joint, and the control becomes unstable.
The belt conveying device of the present invention that can solve such problems and can perform positioning with high accuracy will be described below.

A color image forming apparatus according to a preferred embodiment of the present invention can obtain a continuous signal without a break even if a mark with a seam is used, and this enables stable belt drive control. is there.
In other words, when reading the marks on the belt with an optical sensor, the motor control is used to solve the problem that the signal is interrupted due to seams, dust, scratches, etc. that are generated when marks are generated on the belt at regular intervals. The present invention provides a method of outputting signals or data necessary for motor control without causing problems.
Further, it is possible to eliminate an error due to a phase difference between sensor signals that occurs when two sensor signals are discriminated.

  The endless moving member conveying apparatus as the present embodiment is an endless moving member conveying apparatus that moves (rotates, conveys, etc.) the endless moving member by obtaining driving torque from a motor. It has a position indicator (mark or hole) formed over the entire circumference at regular intervals in the transport direction on the back surface, and is arranged near the endless moving member to detect the passing of the mark or hole described above and send a signal Two or more generated mark sensors 15 (15a, 15b), and an interpolation processing unit that outputs a signal with improved resolution of a signal of a mark interval period output from the mark sensor, the two or more The mark sensors are arranged so as to detect different positions in the moving direction of the marks.

FIG. 6 shows a conceptual diagram of a mark when applied to a conveyor belt as an example of an endless moving member and a mark sensor 15 according to the present invention. The basic configuration of the drive system as the belt conveying device may be the same as that shown in FIG.
In the embodiment of the belt conveying device, a motor and a speed reducer are shown in the driving portion, but the configuration of the driving force source may be any. Further, although the mark is shown on the belt surface as an example, it may be formed on the back surface.

As illustrated in FIG. 6, the mark sensor 15 (15 a, 15 b) is disposed in the vicinity of the conveyance belt 3 so as to be shifted in the moving direction of the marks formed continuously.
The mark sensor may be any means that can detect the formed mark. In the example shown in FIG. 3, the optical sensor detects the mark due to the change in reflectivity. However, when the mark is a magnetic pattern, a magnetic head may be used. It is also possible to use an encoder head by bonding the linear scale.

  Since the mark detection signal is interrupted at the joint portion of the mark, as shown in FIG. 7, it can be determined as the joint portion of the mark by detecting the discontinuous portion of the mark. What is necessary is just to comprise so that it may judge that it is a joint and outputs a joint signal when the period of a sensor signal is counted with a base clock and the count value (period) exceeds a certain threshold value.

Here, when the joint process is to be performed using two sensors, the other sensor signal may be selected and used at the joint portion of the mark.
FIG. 8 shows an example of a waveform when two sensor signals are selected using a joint signal. When selecting a waveform with a joint signal as shown in FIG. 8, if the signal phases of the two sensors (the positions of the edges of the rectangular signal) are not aligned, the position is changed by the phase difference when the signals are switched. It is detected as if a shift has occurred.

  For example, positioning of a color image forming apparatus that is an object of the present invention requires positioning of about 10 μm. If the mark pitch is 100 μm, the maximum mark pitch of 100 μm is measured depending on the phase of two sensors. An error will be produced. Since this measurement error is defined by the (period) resolution of the mark pitch, there is no problem if sufficient resolution is obtained. However, a position detection device such as an encoder having a resolution of 10 μm is expensive and cannot be used for mass-produced products. Further, an endless belt or the like in the image forming apparatus targeted by the present invention is difficult to detect a mark with high resolution due to vertical movement and undulation during conveyance.

  In the present invention, in order to ensure the measurement position accuracy even when the two sensor signals as described above are switched, means for solving the problem by using means for artificially increasing the resolution is provided. In the present invention, in order to solve the above problem, “interpolation processing unit that outputs a high-resolution signal having a period shorter than the period of the detection signal of the position indicator (mark or hole)” is output to each of the mark sensors 15a and 15b. It prepares for. The interpolation processing unit is a part that performs processing having a function of increasing the resolution by interpolating the interval period of the mark signals, and several methods described in the following embodiments can be used.

A signal whose resolution is increased by interpolation (high resolution signal) does not generate a phase difference greater than the period of the interpolation signal even if there is a phase difference between the two sensors.
For example, in the circuit shown in FIG. 9, if the interpolation signal is generated with the same clock as shown in FIG. 10, the phase difference before and after switching the sensor signal to be selected can be completely eliminated, and extremely accurate position detection can be performed. Will be able to.
In the circuit illustrated in FIG. 9, an interpolation processing circuit is provided for the outputs of the sensors 1 and 2, and the two sensor signals are multiplied and added to increase the resolution in a pseudo manner. Even if the phases are different, continuous position data as shown in FIG. 10 can be obtained.

  As shown in FIG. 11, the interpolation processing unit samples the signal of the mark sensor and calculates the period of the signal of the mark sensor, and n-divides the signal period obtained by the signal period calculation unit. A division signal generation unit (period division unit and pulse generation circuit) that generates a periodic signal is provided.

The signal period calculator can calculate the signal period using a counter as shown in the waveform of FIG. If the counter is configured so that the reset is performed by the signal of the mark sensor and counting is performed by the reference clock signal, the count numbers T1, T2,... Tn corresponding to the signal period are obtained as shown in FIG. A value obtained by multiplying Tn by a clock period is a signal period.
The output obtained from the “divided signal generation unit” that generates a pulse having a period obtained by dividing the signal period obtained here by the desired number of divisions by the period dividing unit by the pulse generation circuit is a signal obtained by dividing the sensor signal. At this time, as shown in FIG. 12, the count data is updated when the edge of the mark signal occurs.

As a second embodiment of the interpolation processing unit, for example, a configuration using F / V conversion and a VCO (voltage controlled oscillator) as shown in FIG. 13 may be used.
The F / V converter is a circuit that converts a frequency into a voltage, and can extract a voltage corresponding to the signal frequency. The VCO generates a pulse having a frequency corresponding to the voltage, and has the reverse effect of the F / V converter.
By adjusting the pulse frequency transmitted by the VCO with the voltage corresponding to the frequency obtained by the F / V converter, a pulse having a frequency proportional to the sensor signal frequency can be obtained, and the conversion coefficient is arbitrarily selected. Thus, a signal having a divided period can be obtained.

Furthermore, as a third embodiment of the interpolation processing unit, it may be configured by means for interpolating with a clock signal having a fixed period interval shorter than the signal period of the mark sensor and reset by the signal edge of the mark sensor.
FIG. 14 shows a conceptual diagram of the configuration, and FIG. 15 shows an example of a waveform. As a means for artificially improving the resolution of the mark signal, interpolation may be performed using a clock signal having a fixed period.

  However, since the clock signal has a constant frequency even if the sensor signal period changes, an error occurs if there is a speed fluctuation exceeding one clock period. In the electrophotographic image forming apparatus to be controlled according to the present invention, the photosensitive member, the intermediate transfer belt, the paper, and the like are configured to be conveyed at a constant speed. Can be used.

  Further, when the mark sensor is an analog output type in which a sine wave output can be obtained depending on the presence or absence of a mark, as a fourth embodiment of the interpolation processing unit, a pulse is output for each equal phase from the analog output of the mark sensor according to the signal amplitude value. It can also be configured by a multiplier circuit that generates and increases the resolution.

FIG. 16 shows a waveform obtained by plotting data obtained by dividing a sine wave into 20 angular phases.
The angle phase with respect to the amplitude of the sine wave can be calculated by Asin {amplitude intensity}. However, if it is intended to divide into 20 as in this example, levels of horizontal lines 0.309... 0.588. . 809... And the like as a threshold value to generate a pulse waveform can improve the resolution of the sensor output.
Since the sine wave has peaks at angles of π / 2 and 3π / 2, the amplitude change with respect to the angle is reduced. However, if a signal with a 90 ° phase shift is taken out simultaneously as the output of the mark sensor, the waveform becomes cos θ. As shown in FIG. 16, it is possible to continuously use a portion close to linear, and the accuracy can be further increased.

  As described above, according to the present embodiment, by using two or more sensors, a malfunction caused by dust or a deposit can be supplemented by other sensor outputs. For this reason, a more stable signal output can be obtained.

  In addition, by improving the resolution of the mark sensor over the mark pitch, it is possible to increase the detection resolution and improve the control performance, and eliminate the error due to the phase difference between the sensor signals that occurs when the two sensor signals are discriminated. Thus, highly accurate positioning can be realized.

As for the interpolation processing unit as each embodiment described above, as in the fifth embodiment, a signal failure due to a joint or dust or scratch is detected by a signal from the sensor, and the interpolation signal of the sensor signal is detected even when the signal is defective. It is also possible to generate and output an interpolation signal similar to the state without signal failure without updating or resetting.
FIG. 17 shows a conceptual diagram of an output signal according to the fifth embodiment. In the configuration of each embodiment described above, it has been described that the joint is detected and the position of the sensor signal not detected by the joint is selected to perform position detection. Since the transfer is performed at a constant speed, the accuracy is often not greatly affected even when the interpolation signal is continuously output without being reset at the joint portion. In addition, since the resolution is improved by the interpolation process, the phase error between the two sensors does not exceed the resolution. Therefore, both data may be simultaneously acquired and used as position data.

  According to the fifth embodiment, there is also an effect of expanding the detection area of the mark by reading two sensors simultaneously, so that the adjacent pitch error of the mark can be reduced, and more accurate sensing is possible. .

Further, as another embodiment of the present invention, a configuration having a seam mark sensor (seam sensor means) for detecting a seam of a mark separately from the mark sensor may be adopted.
A configuration example in another embodiment is shown in FIG. For example, when a mark portion is formed in a belt or drum shape by pasting a tape on which a mark is printed in advance, a tape joint appears as a mark joint. At such a joint portion of the mark, a sensor signal Tends to become unstable, and the accuracy near the joint may deteriorate.
Therefore, a signal from a plurality of mark sensors can be obtained by arranging a joint mark (joint target indicator) at the joint portion of the conveyor belt and detecting the joint mark with another sensor such as a dedicated joint mark sensor. Among them, the output signal from the mark sensor that is measuring a position that is not a joint can be reliably selected by the signal selection circuit.

Further, for each of the above-described embodiments, for example, as shown in FIG. 19, a phase comparison circuit for comparing the phases of output signals from a plurality of mark sensors is further provided, and control means is also used using the phase output from the phase comparison circuit. May perform drive control of the drive motor.
According to this configuration, it is possible to obtain a seamless signal output seamlessly according to each of the above-described embodiments, and it is possible to detect not only the conveyance speed of the conveyance belt but also the elongation of the conveyance belt by a change in phase, More accurate motor drive control can be performed.

In addition, in each of the above-described embodiments, if accurate position information is obtained even at a joint portion, when one sensor detects a joint, the other detects a portion that is not a joint. There is a need.
For this reason, it is preferable that the plurality of mark sensors described above are arranged so that when one sensor detects a joint, another sensor detects a portion that is not a joint.

  Further, as described above, the error due to the phase difference between the two sensors is at most equal to or less than the signal resolution. Therefore, it is preferable to perform interpolation processing with a resolution higher than the accuracy of positioning.

In addition, the signal processing parts such as the interpolation processing circuit and the phase comparison circuit shown in the block circuit diagram described above can be configured in software using a DSP (Digital Signal Processor). In the case of performing complicated signal processing, if a DSP is used, it is possible to easily perform operation confirmation, debugging, etc. without configuring the logic circuit with hardware.
That is, the signal processing part may be configured by a computer that performs processing based on a program.

Further, in each of the above-described embodiments, in order to measure the moving speed of the endless moving member in the endless moving member transport apparatus, position indicator portions (marks or holes) are arranged on the entire circumference at substantially constant intervals in the moving direction. Although the movement part interlocked with the movement member has been described as the endless movement member itself, the present invention is not limited to this. For example, a drum-like member, an endless belt, a drum or a belt-like photoreceptor, a transfer belt, or an intermediate transfer It may be a belt, a roller that stretches such an endless belt, a rotary encoder that rotates in conjunction with a driving means (motor), or the like.
When this moving part is applied as an endless belt, the endless moving member conveying device is wound around a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a motor (driving means), and the plurality of rollers. A belt conveyance device including an endless belt is obtained.

When the moving part is applied to a drum or belt-shaped photoconductor, the image forming apparatus forms an image on the paper 2 by the electrophotographic method using the drum or belt-shaped photoconductor.
According to this configuration, the speed / positioning error in the photosensitive member can be extremely reduced, so that high-quality image formation with less magnification error and image distortion is possible.

In addition, when the moving part is applied to a transfer belt or an intermediate transfer belt for transferring an image of an electronic process unit in a color image forming apparatus to a sheet, the speed stability and positioning accuracy of the transfer belt and the intermediate transfer belt are improved. It can be greatly improved.
For this reason, in the tandem type color image forming apparatus as shown in FIG. 1, it is possible to transfer the image from the electronic process unit of each color to the paper 2 with higher accuracy, and to stabilize the speed of the transfer belt and the intermediate transfer belt. Since the influence of image quality and positioning accuracy on image quality is very large, high-quality image output can be obtained by using the present invention.

Further, the moving part can be similarly realized even when applied to a roller that stretches an endless belt or a rotary encoder that rotates in conjunction with a driving means (motor).
That is, even if the position indicator (mark or hole) is disposed on any of a plurality of rollers including the drive roller, or on a rotary encoder, and the like, each of the above-described components is detected by the mark sensor. As in the embodiment, the position indicator can be detected, the speed can be calculated, and a stable signal output can be obtained, so that the drive means can be controlled stably.

In each of the above-described embodiments, the color image forming apparatus has been described as a laser system, but an ink jet system may be used. That is, it may be configured to include a recording head (inkjet image forming unit) that records an image on a sheet by an inkjet method, and to form an image on the sheet using the endless moving member.
In this configuration, the moving part may be a paper transport roller or a paper transport belt.

1 is a diagram illustrating a configuration example of a color image forming apparatus as an embodiment of the present invention. It is a wave form diagram which shows the positioning error by the speed fluctuation | variation of a belt conveying apparatus. It is sectional drawing which shows the structural example of an optical mark sensor. It is a perspective view which shows the basic composition of the drive system as a belt conveying apparatus, and the joint of a mark. It is a wave form diagram which shows the phase difference of a reference clock and a sensor signal. It is a perspective view which shows the mark sensor 15 periphery of the conveyance belt which concerns on this invention. It is a wave form diagram which shows the example which judges the discontinuous part of a mark from count data and a threshold value. It is a wave form diagram which shows an example when two sensor signals are selected using a joint signal. It is a block diagram which shows the outline | summary of the circuit structure in embodiment of this invention. It is a wave form diagram which shows an output signal at the time of producing | generating an interpolation signal with the same clock. It is a block diagram which shows the 1st structural example of an interpolation process part. It is a wave form diagram which shows the example which a signal period calculating part calculates a signal period using a counter. It is a block diagram which shows the 2nd structural example of an interpolation process part. It is a block diagram which shows the 3rd structural example of an interpolation process part. It is a wave form diagram which shows the example of the interpolation clock signal by this 3rd structural example. It is a wave form diagram which shows the example which divided | segmented the sine wave into 20 angle phases as the 4th structural example of an interpolation process part. It is a wave form diagram which shows notionally the output signal by the 5th example of composition of an interpolation processing part. It is a perspective view which shows the mark sensor 15 periphery by other embodiment of this invention. It is a block diagram which shows the outline | summary of a circuit structure at the time of further providing a phase comparison circuit.

Explanation of symbols

1K, 1M, 1Y, 1C Electronic process part 2 Paper (recording paper)
3 Conveyor belt (endless moving member and moving part)
4, 5 Transport roller 6 Paper feed tray 7 Photosensitive drum 8 Charger 9 Exposure unit 10 Developer 11 Photoconductor cleaner 12 Exposure light (laser beam)
13 Transfer Device 14 Fixing Device 15 Mark Sensor (Sensor Means)

Claims (17)

An endless moving member conveying device that moves the endless moving member by power from a driving means,
Position marking portions are arranged over the entire circumference at substantially constant intervals in the moving direction in the moving portion,
Two or more sensor means for detecting the passage of the position indicator when the moving part moves and outputting a signal detect the position indicator at different positions in the moving direction of the moving part. Arranged so that
Interpolation processing means for outputting a high-resolution signal having a cycle shorter than the cycle of the detection signal of the position indicator output from the sensor unit;
An endless moving member conveying apparatus comprising: a control unit that controls the driving unit based on an output from the interpolation processing unit. The interpolation processing means includes
Sampling a detection signal of the position indicator from the sensor means and calculating a period of the detection signal;
The endless moving member conveying device according to claim 1, further comprising: a divided signal generating unit that generates a periodic signal obtained by dividing the signal period calculated by the signal period calculating unit into n.   The interpolation processing means uses the clock signal with a constant cycle interval that resets the high resolution signal having a cycle shorter than the cycle of the detection signal of the position indicator outputted from the sensor unit. The endless moving member conveying device according to claim 1, wherein the endless moving member conveying device is generated.   The endless moving member conveying apparatus according to claim 1, wherein the interpolation processing means is configured by a computer that performs processing based on a program. The sensor means is an analog output type that performs sinusoidal output depending on the presence or absence of a detection signal of the position indicator,
2. An endless moving member conveying apparatus according to claim 1, wherein said interpolation processing means comprises a multiplier circuit for generating a pulse for every equal phase from the analog output of said sensor means for increasing the resolution.   The said interpolation process means produces | generates and outputs the interpolation signal similar to the state without a signal defect at the time of the signal defect of the detection signal from the said sensor means, The output of any one of Claim 1 to 5 characterized by the above-mentioned. The endless moving member conveying apparatus as described. It further comprises a seam sensor means for detecting a seam of the position indicator disposed on the moving part,
7. The signal from the sensor means that measures a position that is not a joint is selected from the output signals from the two or more sensor means based on the detection result by the joint sensor means. The endless moving member conveying device according to claim 1. A phase comparison circuit for comparing phases of output signals from the two or more sensor means;
8. The endless moving member conveying apparatus according to claim 1, wherein the control unit further controls the driving unit by further using an output from the phase comparison circuit. 9.   2. The two or more sensor means are attached so as to have an interval wider than a width of a seam generated when the position indicator is formed on the entire circumference of the moving part. The endless moving member conveying device according to any one of 1 to 8.   10. The endless moving member conveying apparatus according to claim 1, wherein the resolution improved by the interpolation processing unit is higher than a required accuracy for positioning the endless moving member. 11.   The endless moving member conveyance device according to any one of claims 1 to 10, wherein the moving portion is a drum-shaped member. The moving part is the front or back surface of the endless moving member, the endless moving member is an endless belt,
The endless moving member conveying device is a belt conveying device including a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a driving unit, and the endless belt stretched around the plurality of rollers. The endless moving member conveying device according to any one of claims 1 to 11, wherein the conveying device is an endless moving member conveying device. The endless moving member conveying device is a belt conveying device including a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a driving unit, and the endless moving member that is stretched over the plurality of rollers.
The endless moving member conveying device according to any one of claims 1 to 11, wherein the moving portion is any of a roller that stretches the endless moving member. The endless moving member conveying device is a belt conveying device including a plurality of rollers including a driving roller that rotates by obtaining a driving torque from a driving unit, and the endless moving member that is stretched over the plurality of rollers.
The endless moving member conveying device according to any one of claims 1 to 11, wherein the moving portion is a rotary encoder interlocking with the driving unit. An endless moving member conveying apparatus according to any one of claims 1 to 14, and an electronic process unit using an electrophotographic method for forming an image of each color on a sheet,
The image forming apparatus, wherein the moving part is a photosensitive belt in the electronic process unit. An endless moving member conveying device according to any one of claims 1 to 14, and an electronic process unit for forming an image on a sheet,
The image forming apparatus, wherein the moving part is a transfer belt or an intermediate transfer belt for transferring an image of the electronic process unit onto a sheet. An endless moving member conveying device according to any one of claims 1 to 14, and an inkjet image forming unit that forms an image on a sheet by an inkjet method,
The image forming apparatus according to claim 1, wherein the moving part is a paper transport roller or a paper transport belt.

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