JP4676746B2 - Drive control device and image forming apparatus - Google Patents

Description

This invention is an endless belt member and a drum-shaped member endless moving member appropriately endless moved so that drive motion control devices, etc., and a copying machine equipped with it, a printer, an image forming apparatus of the facsimile apparatus or the like.

  As an electrophotographic image forming apparatus, monochromatic images formed by a plurality of monochromatic toners respectively formed on a plurality of photosensitive members (first image carriers) are sequentially transferred onto an intermediate transfer member (second image carrier). Then, a plurality of primary transfer portions (primary transfer means) for forming a composite color image obtained by superimposing the single color images, and a composite color image formed on the intermediate transfer body thereby are collectively transferred onto a sheet. With a secondary transfer section (secondary transfer means) that sequentially transfers single-color images with respective single-color toners that are sequentially formed on the photosensitive member onto the intermediate transfer member, and then superimposes the single-color images. Some include a primary transfer unit that forms a composite color image and a secondary transfer unit that collectively transfers the composite color image formed on the intermediate transfer body onto a sheet.

In such an image forming apparatus, that is, in an image forming apparatus provided with an endless moving member (an endless belt member or a drum-like member) for image formation such as a belt-shaped or drum-shaped photoreceptor or an intermediate transfer member, an endless moving member In addition, in order to accurately position the image (toner image) on the paper (transfer material) conveyed by it, the amount and position of movement of the endless moving member (actually its moving surface) must be controlled accurately. Is required.
However, an endless drum-like member (photosensitive drum or intermediate transfer drum) that is an endless moving member or an endless belt-like member (photosensitive belt or intermediate transfer belt) is driven by a driving roller (rotating body). When the rotational angular velocity fluctuates for some reason, the moving speed, moving amount, and moving position of the endless moving member also fluctuate, and the position error of the image on the endless moving member and the paper conveyed by it is suppressed with high accuracy. There is a problem that becomes difficult.

  Therefore, in order to solve such problems, an endless drum-like member and a driving roller (for moving the endless belt-like member) are endless in order to suppress an image position error due to a change in rotational angular velocity with high accuracy. A rotary encoder is directly connected to the rotating shaft of the drum-shaped member and the rotating shaft of the driving roller, and the endless drum-shaped member and the driving roller are driven based on the rotational angular velocity of the endless drum-shaped member and the driving roller detected by the rotary encoder. There has been proposed an image forming apparatus that controls the rotational angular velocity of a drive motor as a means (see, for example, Patent Document 1). This image forming apparatus indirectly controls the movement amount (movement position) of the endless drum-like member or endless belt-like member by controlling the rotational angular velocity of the endless drum-like member or drive roller.

On the other hand, marks (or holes) are formed on the outer peripheral surface (front surface) or inner peripheral surface (back surface) of the belt (endless belt-like member) so as to be continuous at a predetermined interval along the moving direction, and the mark is formed by a sensor There has also been proposed an image forming apparatus in which the moving speed of the belt surface is calculated from the detected pulse interval and fed back to drive control (see, for example, Patent Documents 2 to 4). According to this image forming apparatus, since the behavior of the belt surface can be directly observed, the movement amount can be directly controlled. Thereby, it is possible to reduce the measurement error due to the eccentricity of the driving roller for driving the belt, the slippage of the driving roller and the belt, and the thickness deviation of the belt.
Japanese Patent No. 3107259 JP-A-6-263281 JP-A-9-114348 JP 11-24507 A

  However, in the image forming apparatus that directly controls the amount of movement of the belt surface as described above, it is effective when a stable signal output is possible like a rotary encoder, but when a mark is formed on the belt surface, When the mark is detected by an optical sensor (using a light-emitting element and a light-receiving element), the output of the optical sensor (light-receiving element) is stabilized by environmental changes such as the surrounding temperature change and the deterioration of the optical sensor itself over time. However, there is a problem that the image quality is adversely affected.

Also, in an image forming apparatus that directly controls the amount of movement of the belt surface, it is effective when a continuous signal output is possible like a rotary encoder, but when a mark is formed on the belt surface, If there is, there is a problem that an error occurs in the speed measurement at that portion and the operation becomes unstable.
In the above-described image forming apparatuses described in Patent Documents 2 to 4, the mark formation method on the belt surface is not mentioned, but marks at regular intervals (constant intervals) are not cut off due to the flexibility of the belt and the circumferential length deviation. It is very difficult to process the entire circumference.

  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 the fact that it is not applied or due to the strain inside the belt after molding, the resulting marks are not at regular intervals. Even when printing and adhesion are considered, if the belt circumference tolerance is 0.2 to 0.3%, a belt with a circumference of 500 mm has a deviation of 1 mm or more, and a mark is formed without a break (seam). It turns out to be very difficult to do.

In addition to the mark breaks described above, even if the marks become dirty or scratched, the optical sensor will not be able to detect the marks, resulting in breaks in the signal output. It is likely that the mark is likely to get dirty or scratched because there is a factor in the vicinity of the belt.
Therefore, as a method of performing stable control even when a break occurs in the signal output of the optical sensor due to a break in the mark, it is possible to detect a break in the mark and another control is performed when a break in the mark is detected. A method of performing stable control by switching to the method can be considered. However, in order to perform this method, means and a method for detecting mark breaks, dirt and scratches are required.

Therefore, the following may be considered.
Since the mark breaks that are created during the process of creating marks on the belt are known from the beginning, the presence and position of the marks are known. For example, the mark breaks using a dedicated mark and an optical sensor to detect only the mark breaks. Stable control can be performed by enabling detection of a break and switching to another control method when a mark break is detected.
However, dirt and scratches often appear while the device is being used, not at the time of device creation, and since it is not known in which part of the mark on the belt surface it is the same without providing a dedicated mark. It is necessary to be able to detect mark breaks, dirt and scratches from the mark.

  The present invention has been made in view of the above points, and even when the mark on the endless moving member is detected by an optical sensor, the output of the optical sensor can be used to change the ambient temperature, the deterioration of the optical sensor itself over time, etc. It aims to stabilize regardless of environmental changes. In addition, without using a dedicated mark and optical sensor, marks corresponding to discontinuous parts (mark breaks) and defective parts such as dirt and scratches where the distance between the marks on the endless moving member is outside the predetermined range It is also an object to make it possible to accurately detect the undetectable part.

The present invention, for achieving the above object, there is provided a drive motion control apparatus, and an image forming apparatus having the same.

The drive control device according to the first aspect of the present invention has a light emitting element and a light receiving element, and includes a plurality of marks (even holes) formed so as to be continuous at equal intervals along the endless moving direction of the endless moving member that moves endlessly. Is detected optically, and an analog signal continuously modulated by the presence or absence of a mark due to the movement of the endless moving member is output from the light receiving element (for example, the movement amount of the endless moving member is a sine wave with a DC component as a direct current component). which is an electrical signal obtained by superimposing an AC signal output into an analog alternating signal) and the optical science sensor, and binarization means for converting the analog signal into a binary signal output from the light receiving element, the light receiving element a plurality of comparing means for comparing the averaging means for outputting an analog signal by averaging, a different predetermined reference value an output value of the averaging means is output from the control signal based on the binary signal And control means for controlling the speed or position control of the endless moving member with, in accordance with a combination of comparison results of the plurality of comparing means, which switches the drive current of the light emitting device in stages.

Drive control unit according to the second aspect of the present invention, in the driving control device of claim 1, is provided with a temperature compensation means for stabilizing the output of the light receiving element.
Drive control unit according to the invention of claim 3 is the drive control apparatus according to claim 2, in which the temperature compensating means provided on the output side of the light receiving element.

Drive control unit according to the fourth aspect of the present invention, in the driving control device of claim 2, in which the temperature compensating means provided on the output side of the light amount adjusting means.
Drive control unit according to the invention of claim 5 is the drive control apparatus according to claim 2, in which the temperature compensating means provided on both the output side of the output side and the light amount adjusting means of the light receiving element.
Drive control unit according to the invention of claim 6, in any of the drive control apparatus according to claim 2 to 5, in which using a thermistor to said temperature compensating means.

Drive control unit according to the invention of claim 7, in any of the drive control device of claims 1 to 6, discontinuities such as cut mark undetectable portion (mark the outside spacing of the marks is predetermined It is determined from the change in the output of the analog signal (especially the change in the amplitude of the sine wave AC signal) whether or not a corresponding portion (corresponding to a defective portion such as a portion or dirt or scratch) exists in the detection region of the optical sensor. Further, an error detection means for outputting an error signal when the mark undetectable part is present in the detection area is provided.

The drive control device according to the invention of claim 8, in the driving control device of claim 7, said error detection means includes averaging means for averaging the analog signal outputted from the optical sensor, of the averaging means By comparing the output value with a predetermined reference value, it is determined whether or not the mark non-detectable part exists in the detection area of the optical sensor. If the mark non-detectable part exists in the detection area, an error occurs. A signal is output.
Drive control unit according to the invention of claim 9, in the driving control device of claim 8, in which the averaging means of said error detection means and a low pass filter.

Drive control unit according to the invention of claim 10, in the driving control device of claim 7, said error detection means, by comparing the output value of the averaging means with a predetermined reference value, is the mark undetectable portions It is determined whether or not the detection area of the optical sensor exists, and an error signal is output when the mark non-detectable portion exists in the detection area .

Drive control unit according to the invention of claim 1 1, in the drive control apparatus according to claim 7 or 10, on the basis of the output of said error detection means, not the mark undetectable portion to the detection region of the optical sensor is present If this is recognized, speed control or position control is performed using a control signal based on the binarized signal output from the binarizing means, and the mark undetectable portion exists in the detection area of the optical sensor. When it is recognized that this is the case, speed / position control means for performing speed control or position control different from that in the case where the mark non-detectable portion does not exist in the detection area of the optical sensor is provided.

Drive control unit according to the invention of claim 1 2, in the drive control apparatus according to claim 8 or 9, a plurality of upper Symbol error detection unit, a low-pass filter whose respective cut-off frequency averaging means for each error detecting unit is different And error signal selection means for selecting and outputting any one of the error signals output from the plurality of error detection means according to the moving speed of the endless moving member.

Drive control unit according to the invention of claim 1 3, in the driving control device of claim 1 2, based on an output of said error signal selecting means, not the mark undetectable portion to the detection region of the optical sensor is present If this is recognized, speed control or position control is performed using a control signal based on the binarized signal output from the binarizing means, and the mark undetectable portion exists in the detection area of the optical sensor. When it is recognized that this is the case, speed / position control means for performing speed control or position control different from that in the case where the mark non-detectable portion does not exist in the detection area of the optical sensor is provided.
Drive control unit according to the invention of claim 1 4, in any one of the drive control apparatus according to claim 1-1 3, is obtained by the endless moving member and the belt or drum.

The image forming apparatus according to the invention of claim 1 5, claim 1-1 3 of any of the drive controller and the endless moving member in which a plurality of marks are formed continuously at equal intervals along the endless moving direction And a driving force transmitting means for transmitting the driving force for endlessly moving the endless moving member to the endless moving member, so that the drive control device performs drive control of the driving force transmitting means. It is a thing.
The image forming apparatus according to the invention of claim 1 6, in the image forming apparatus according to claim 1 5, the endless moving member, the conveyor belt, a transfer belt, an intermediate transfer belt, a photosensitive belt, a transfer drum, an intermediate transfer drum, the photosensitive One of the body drums.

According to the drive control apparatus of the present invention, the analog signal output from the light receiving element of the optical sensor for detecting the mark on the endless moving member is averaged and output, and based on the output, the light emitting element of the optical sensor is output. By adjusting the amount of light, the output of the optical sensor can be stabilized regardless of environmental changes. In other words, even when the mark on the endless moving member is detected by the optical sensor, the output change of the optical sensor due to the environmental change such as the ambient temperature change or the deterioration of the optical sensor itself over time can be suppressed (the output of the optical sensor can be Therefore, it is possible to prevent deterioration in edge accuracy of the binarized signal from the binarizing means . Therefore, by performing speed control or position control of the endless moving member using the control signal based on the binarized signal, it is possible to appropriately perform speed control or position control of the endless moving member without increasing the cost. .

Further, it is determined from the change in the output of the optical sensor whether or not the mark detection impossible portion where the mark interval on the endless moving member is outside the predetermined range exists in the detection region of the optical sensor. By outputting an error signal when it exists in the detection area, it is possible to detect a mark non- detectable portion in the endless moving member. That is, it is possible to accurately detect a mark non-detectable portion in the endless moving member without using a dedicated mark and an optical sensor.

According to the image forming apparatus of the present invention, by using the drive control device, appropriate image formation can be performed without increasing the cost, and the image quality can be improved.

Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 2 is a block diagram showing an internal configuration example of a color copying machine which is an embodiment of the image forming apparatus according to the present invention.

  This color copying machine is an electrophotographic apparatus of a tandem type indirect transfer system, and includes a plurality of (four in this example) sheet feeding cassettes 22 on which sheets P are stacked at the lower part of a copying machine body (apparatus body) 1. A paper feeding bank (paper feeding unit) 2, an automatic document feeding unit (hereinafter referred to as “ADF”) 3 that automatically feeds a document onto the contact glass 31 (FIG. 2), and a printer at the center. The sections (image forming sections) 20 are respectively arranged. Note that it is possible to add another sheet feeding unit to the sheet feeding bank 2 as necessary.

An operation unit (not shown) is provided on the upper surface of the copying machine main body 1 on the front side of the ADF 3, and there are a start key for starting a copying operation, a numeric keypad for setting the number of copies, a duplex mode ( Various modes including a mode for forming images on both the front and back sides of the paper, keys for selecting paper size, copy density, etc., a liquid crystal display for performing various displays, and the like.
A scanner unit 23 that reads a document image is provided above the printer unit 20, and a paper discharge tray (paper discharge storage unit) 24 is provided on the left side of the printer unit 20 in FIG. The sheet P on which the image is formed is discharged and stored.

  The printer unit 20 has a drum-shaped photoreceptor (hereinafter referred to as a “photoreceptor drum”) serving as a plurality of first image carriers on which the surface (however, which has been charged in advance) is exposed to form an electrostatic latent image. 26Y, 26M, 26C, and 26K (hereinafter collectively referred to as “photosensitive drum 26”), and electrostatic latent images formed on the surfaces of the respective photosensitive drums 26 are visualized with toners of respective colors. Each of the developing units 63 that form a single-color toner image (hereinafter referred to as a “single-color image”) and the single-color images formed on the respective photosensitive drums 26 are sequentially primary-transferred to form a four-color superimposed image. A drum-shaped intermediate transfer member (hereinafter referred to as “intermediate transfer belt”) 25, which is a second image carrier on which a composite color image is formed, is provided. The intermediate transfer belt 25 rotates in the direction of arrow A. It comes to move.

Around each photosensitive drum 26 (26Y, 26M, 26C, 26K) shown in FIG. 2, each charging unit 62 that uniformly charges the surface of each photosensitive drum 26, and each photosensitive drum Each photoconductor for performing a cleaning process for removing and collecting untransferred toner (residual toner) remaining on each photoconductive drum 26 after primary transfer of the monochrome image (visible image) on the photoconductive drum 26 to the intermediate transfer belt 25 A cleaning unit 64 is provided.
The upper part of the printer unit 20 is irradiated with laser light corresponding to the image information of each color on the exposure position (charged surface) on each photosensitive drum 26 of the printer unit 20, and the electrostatic latent image is applied thereto. An exposure unit 7 is provided to form

  Further, a registration roller 33 constituting a registration unit is provided on the upstream side of the paper conveyance of the printer unit 20 and a fixing unit 28 is provided on the downstream side of the paper conveyance of the printer unit 20, and skew correction of the paper is performed by the registration roller 33. The sheet is fed to the secondary transfer portion between the intermediate transfer belt 25 and the secondary transfer counter roller 54 in timing with the toner image on the photosensitive drum 26. In the secondary transfer portion, the composite color image carried on the intermediate transfer belt 25 is sequentially applied to the paper P fed from any of the paper feed cassettes 22 or the manual paper feed tray 70 in the paper feed bank 2. After the transfer, the combined color image is fixed by applying heat and pressure at the fixing unit 28. On the downstream side of the fixing unit 28, a paper discharge roller 41 that discharges the paper that has passed through the fixing unit 28 onto the paper discharge tray 24 is provided.

Now, when making a copy using this color copying machine, the user sets a document on the document table of the ADF 3. Alternatively, the ADF 3 is opened, a document is set on the contact glass 31 of the scanner unit 23, and the ADF 3 is closed and pressed by it.
When the start key on the operation unit is pressed, the color copying machine performs the following operation.
That is, first, when a document is set on the document table of the ADF 3, after the document is automatically fed onto the contact glass 31, when the document is directly set on the contact glass 31, Then, the scanner unit 23 is driven, and the first traveling body 32a and the second traveling body 32b are reciprocated in the left-right direction in FIG.

  Then, the light source for illuminating the document is turned on by the first traveling body 32a, and the reflected light from the document surface is further reflected toward the second traveling body 32b and reflected by the mirror of the second traveling body 32b to form the imaging lens. 34 is put into a CCD (reading sensor) 35 to read the image of the original. At this time, photoelectric conversion is performed for each color separation light of R (red), G (green), and B (blue), and electrical R, G, and B image signals are output. The RGB image signal is digitized and subjected to image processing, and is sent to the exposure unit 7 as an image signal of yellow (Y), magenta (M), cyan (C), and black (K). By being driven by a modulation method such as PM (Phase Modulation) or PWM (Pulse Width Modulation), laser light corresponding to the document image is emitted. Then, the charged surface (by the charging unit 62) of each photosensitive drum 26 is exposed by the laser light through a polygon mirror and a lens (not shown), and an electrostatic latent image is formed there.

In addition, when the start key is pressed, the driving roller 51 is rotationally driven by a driving motor (not shown), the other rollers 52 and 53 are driven to rotate, and the intermediate transfer belt 25 is rotated. At the same time, each of the photosensitive drums 26 is rotated by the printer unit 20, and each single color toner of Y, M, C, and K is attached to each electrostatic latent image on each photosensitive drum 26 by each developing unit 63. Toner image (single color image) is formed.
Then, as the intermediate transfer belt 25 rotates, the monochrome images are sequentially transferred to form a four-color superimposed composite color image on the intermediate transfer belt 25.

  That is, first, the Y image (yellow image) on the photosensitive drum 26Y is primary-transferred by the primary transfer roller 65 (FIG. 3) onto the intermediate transfer belt 25 rotating in the arrow A direction in FIG. Next, when the Y image moves to the position of the photosensitive drum 26M, the M image (magenta image) is superimposed on the Y image and is primarily transferred by the primary transfer roller 65. When the portion to which the M image has been transferred has moved to the position of the photosensitive drum 26C, the C image (cyan image) is superposed thereon and primary transferred by the primary transfer roller 65, and the C image is further transferred. When the transferred portion moves to the position of the photosensitive drum 26K, a K image (black color image) is superimposed thereon and is primarily transferred by the primary transfer roller 65.

Then, the combined color image obtained by superimposing the four colors Y, M, C, and K is rotated by the intermediate transfer belt 25 so that the secondary transfer roller 53 positioned on the inner side and the secondary transfer counter roller positioned on the outer side. When the sheet is moved to the secondary transfer position between the second transfer roller 53 and the sheet (recording sheet) fed in synchronism with the timing, the second transfer roller 53 performs batch transfer.
As described above, the color copying machine performs an image forming process in which the intermediate transfer belt 25 rotates once to form one composite color image.
After the four-color superimposed composite color image on the intermediate transfer belt 25 is collectively transferred onto the paper, the untransferred toner remaining on the intermediate transfer belt 25 is transferred by the intermediate transfer cleaning unit (belt cleaning unit) 55. Removed and recovered.

The paper on which the composite color image has been fixed and passed through the fixing unit 28 is discharged to the paper discharge tray 24 by the paper discharge roller 41 when the single-sided mode (mode for forming an image only on one side of the paper) is set. Is done.
In addition, when the duplex mode is set, the paper is disposed below the printer unit 20 by the branching claw 43 provided on the conveyance path between the fixing unit 28 and the paper discharge roller 41. The sheet is fed to the double-sided portion 29, reversed, and conveyed again to the registration roller 33. This time, after a composite color image is formed on the back surface (second surface), the sheet is discharged onto the discharge tray 24 by the discharge roller 41. Is done.

On the other hand, the paper feed bank 2 for feeding paper is provided with a paper feed unit 4 for each paper feed stage.
The paper feed unit 4 of each paper feed stage includes a bottom plate 5 on which the paper P is stacked, and a pickup roller 6 that feeds the paper P stacked on the bottom plate 5 by rotating it counterclockwise in FIG. Further, when there are a plurality of sheets P fed by the pickup roller 6, there is provided a separating means 8 composed of a feed roller and a reverse roller for separating the sheet P into a single sheet.
The sheet feeding unit 4 feeds the unused sheet P stored on the bottom plate 5 of the sheet feeding cassette 22 so that the sheet positioned at the uppermost position is moved up by the bottom plate 5 turning upward. As the pickup roller 6 rotates in this state, the sheet is fed out from the sheet feeding cassette 22.

  Therefore, when two or more sheets P are sent out, they are separated into one sheet by the separating means 8. Then, the sheet P is conveyed to the registration roller 33 in a stopped state, where it is temporarily stopped, and at the timing at which the positional relationship between the leading end and the composite color image on the intermediate transfer belt 25 exactly coincides with the registration roller 33. When the roller 33 starts rotating, it is conveyed toward the printer unit 20. Thereafter, image formation is performed through the above-described process, and the image is discharged to the discharge tray 24.

  As described above, this color copying machine scans an original, reads the image, digitizes the image information, and forms an image on a sheet. This is a multi-function image forming apparatus having a function as a facsimile apparatus that exchanges image information with a remote place and a function as a printer that prints image information handled by a computer on paper. Then, all images formed by any function are discharged to one discharge tray 24.

Next, the printer unit 20 will be specifically described with reference to FIG.
FIG. 3 is a configuration diagram showing the configuration of the printer unit 20 in detail.
As described above, the printer unit 20 includes the charging unit 62, the developing unit 63, the primary transfer roller (primary transfer unit) 65, and the photosensitive member cleaning unit 64 around each photosensitive drum 26. In order to perform the image formation, an electrostatic latent image corresponding to each color is formed on each photosensitive drum 26, and a toner image is formed by attaching toner of each color to each electrostatic latent image. A tandem image forming unit that forms a four-color composite color image on the intermediate transfer belt 25 by sequentially primary-transferring each color toner image onto the intermediate transfer belt 25 by each primary transfer roller 65. is there.

Each charging unit 62 is a roller-shaped contact charging member (charging roller), and uniformly charges the surface of the photosensitive drum 26 by applying a voltage by contacting the corresponding photosensitive drum 26. Of course, charging can be performed by a contact charging member other than the roller shape or a non-contact scorotron charger.
Each developing unit 63 may use a one-component developer, but in the illustrated example, a two-component developer composed of a magnetic carrier and a non-magnetic toner is used. Then, the agitation unit that conveys the two-component developer while stirring and supplies and adheres the two-component developer to the developing sleeve, and transfers the toner of the two-component developer attached to the developing sleeve to the photosensitive drum 26. And the developing unit is positioned lower than the developing unit.

Each primary transfer roller 65 is a roller-like contact transfer member, and primary-transfers the corresponding monochrome image on the photosensitive drum 26 onto the intermediate transfer belt 25. Of course, primary transfer can also be performed with a contact transfer member other than a roller or a non-contact scorotron charger.
Each photoconductor cleaning unit 64 removes and collects untransferred toner remaining on the corresponding photoconductor drum 26.

The intermediate transfer belt 25 is stretched between the driving roller 51, the driven roller 52, and the secondary transfer roller 53, and is rotatable in the A direction.
An intermediate transfer cleaning unit 55 is provided on the surface of the portion of the intermediate transfer belt 25 that is stretched between the driven roller 52 and the secondary transfer roller 53.

The secondary transfer roller 53 is a roller-like contact transfer member that constitutes a secondary transfer portion together with the secondary transfer counter roller 54, and collectively transfers the composite color image formed on the intermediate transfer belt 25 onto a sheet. Of course, the secondary transfer can be performed by a contact transfer member other than the roller shape or a non-contact scorotron charger.
The intermediate transfer cleaning unit 55 removes and collects untransferred toner remaining on the surface after image transfer by the intermediate transfer belt 25.

  A high voltage power supply unit (not shown) is connected to each primary transfer roller 65, secondary transfer roller 53, and intermediate transfer cleaning unit 55. The high-voltage power supply unit applies a predetermined bias voltage to each primary transfer roller 65 in order to primarily transfer a monochrome image formed on each photosensitive drum 26 onto the intermediate transfer belt 25. I do. Further, a secondary transfer process is performed in which a predetermined bias voltage is applied to the secondary transfer roller 53 in order to secondarily transfer the composite color image formed on the intermediate transfer belt 25 onto the sheet. Further, a predetermined bias voltage is applied to the intermediate transfer cleaning unit 55 in order to remove the untransferred toner remaining on the intermediate transfer belt 25.

Next, the parts related to the present invention in this color copying machine will be described in detail with reference to FIGS.
FIG. 4 is a diagram showing a configuration example of a belt drive device that constitutes the intermediate transfer belt 25 of FIG. 3 and its peripheral drive system and control system.
In this belt driving device, the intermediate transfer belt 25, which is an endless belt-like member (endless moving member), is continuously arranged at equal intervals (predetermined intervals) along the rotation direction (endless moving direction) of the intermediate transfer belt 25. Thus, a scale 250 having a plurality of marks (reflection portions) is provided.

  The drive control device 100 uses a microcomputer (CPU) that functions as a speed / position control means, and uses an intermediate transfer belt 25 using a control signal based on the output of the mark sensor 110 that detects a mark on the scale 250. Speed control or position control is performed. That is, the speed (moving speed) of the outer peripheral surface (front surface) of the intermediate transfer belt 25 is calculated from the pulse interval (binary signal described later) obtained by detecting the mark on the scale 250 by the mark sensor 110. The calculation result is fed back to the control, and a corresponding control signal is output to the drive motor 120 to drive and control the drive motor 120, whereby the outer periphery of the intermediate transfer belt 25 is driven via the gears 121 and 122 and the drive roller 51. The surface speed or position is controlled to an optimum value.

The drive motor 120, the gears 121 and 122, and the drive roller 51 correspond to drive force transmission means for transmitting a drive force for rotating (endlessly moving) the intermediate transfer belt 25 to the intermediate transfer belt 25.
Further, the mark sensor 110 is an optical sensor, and may be the entire mark detection device or a part thereof (for example, a combination of a light emitting element and a light receiving element). In this embodiment, mark detection is performed. The entire device. Further, the mark sensor 110 only needs to be connected to the drive control device 100, and therefore may be a part of the drive control device 100 or may be separated from the drive control device 100.

  FIG. 5 is a configuration diagram showing an example of the scale 250 and the mark sensor 110 (optical sensor) provided on the inner peripheral surface of the intermediate transfer belt 25, and (a) is a front view of a part of the scale 250 as viewed from above. (B) is a diagram showing the configuration and optical path of the optical system of the mark sensor 110, and (c) is a front view of the mark sensor 110 as viewed from above.

The scale 250 is a reflective scale, and includes a reflection portion (mark) 251 and a light shielding portion 252 that are shown by oblique lines along the rotation direction A on the inner peripheral surface (or the outer peripheral surface) of the intermediate transfer belt 25. It is formed alternately (formed so that the reflection portions 251 are continuous at equal intervals). For example, aluminum having high reflectivity is used for the reflecting portion 251.
The mark sensor 110 includes a light emitting element (LED or the like) 111, a collimating lens 112, a slit mask 113, a glass 114 (may be a transparent cover such as a transparent resin film), a light receiving element (phototransistor or the like) 115, and the like. Yes.

In the mark sensor 110, a beam (light beam) emitted from the light emitting element (light source) 111 and converted into parallel light by the collimator lens 112 passes through a slit mask (sensor slit member) 113 including a plurality of slits parallel to the scale 250. The beam LB is divided into a plurality of (three in this example) beams LB, is incident on the scale 250 of the intermediate transfer belt 25, and a part thereof is reflected by the reflecting portion 251.
A plurality of split beams LB, which are light reflected by the reflecting portion 251 of the scale 250 of the intermediate transfer belt 25, are received by the light receiving element 115 through the glass 114 of the mark sensor 110, and the change in brightness of the reflected light is detected by an electrical signal. Convert to

Therefore, the light receiving element 115 of the mark sensor 110 detects the reflection portion (mark) 251 of the scale 250 by receiving the reflected light, and is continuously modulated by the presence or absence of the reflection portion 251 due to the rotation of the intermediate transfer belt 25. An analog alternating signal (analog signal) can be output (the movement amount of the intermediate transfer belt 25 is converted into an electric signal obtained by superimposing a sine AC signal on a DC component and output).
Here, the slit mask 113 and the glass 114 positioned in the beam optical path on the surface of the mark sensor 110 are defined as a mark detection region (detection region of the optical sensor). As the slit mask 113, a photoemulsion type optical slit may be used.

FIG. 6 is a diagram illustrating a state in which dirt (dust) is attached to the mark detection area of the mark sensor 110.
FIG. 7 is a diagram showing waveform examples of various signals when the mark sensor 110 detects a mark. FIG. 7A shows waveform examples of various analog alternating signals (sensor analog signals) output from the mark sensor 110. b) each shows a waveform example of a binarized signal obtained by binarizing an analog alternating signal.

Here, the analog alternating signal corresponds to an electrical signal obtained by superimposing a sine wave AC signal on a DC component (which varies slightly due to variations in reflectance or transmittance, fluctuations in detection distance, etc.).
As can be seen from FIG. 7, the analog alternating signal output from the light receiving element 115 of the mark sensor 110 depends on the presence or absence of dust adhering to the mark detection area (dirt of the mark detection unit) and the amount of dust (dirt). The waveform is different.
For example, as shown in FIG. 6, if dust adheres to the mark detection area of the mark sensor 110, the beam from the light emitting element 111 is thereby blocked, and the amount of light that can be received by the light receiving element 115 is reduced. The output level of the signal (analog alternating signal) decreases.

  If it does so, it will become difficult to convert from an analog alternating signal to the binarization signal used in the case of control. Although not shown, the mark sensor (optical) is changed depending on the temperature characteristics (change in characteristics due to temperature) of the light emitting element (LED or the like) 111 or the light receiving element (phototransistor or the like) 115 constituting the mark sensor 110. The characteristics of the sensor 110 also change with temperature, and the output level fluctuates as shown in FIG. In the case of temperature characteristics, the output level increases or decreases based on the characteristics at room temperature.

  FIG. 8 shows a case where the mark sensor 110 cannot detect a mark (corresponding to a mark non-detectable portion) when the color copying machine performs a low speed copy (normal copy) (when the intermediate transfer belt rotates at a low speed). FIG. 4 is a diagram illustrating waveform examples of various signals, where (a) corresponds to a waveform example of an analog alternating signal output from the light receiving element 115 of the mark sensor 110, and (b) and (c) correspond to the analog alternating signal. 2 shows waveform examples of signals output from respective circuits to be described later.

  FIG. 9 is a diagram showing waveform examples of various signals when the mark sensor 110 cannot detect a mark when the color copying machine performs high-speed copying (when the intermediate transfer belt rotates at high speed). (A) is a waveform example of an analog alternating signal output from the light receiving element 115 of the mark sensor 110, and (b) and (c) are waveforms of signals output from respective circuits described later corresponding to the analog alternating signal. Each example is shown.

FIG. 1 is a block diagram showing a configuration example of a control system (mark detection circuit) of the mark sensor 110 of FIG.
In the mark sensor 110, a light receiving element (in this example, an NPN type phototransistor) 115 constituting the sensor unit 201 (including the light emitting element 111, the collimating lens 112, the slit mask 113, the glass 114, the light receiving element 115, and the like) described above. Are connected to a predetermined power source, and the emitter terminal is grounded via a resistor (RL) 301.

In addition, an amplifier 302 and a binarization circuit 303 are connected in series between the connection point between the collector terminal of the light receiving element 115 and the resistor 301 and the output terminal of the mark signal, and a temperature compensation circuit (temperature compensation means) ) Is connected in parallel with the amplifier 302.
Further, an LPF (low-pass filter) 305 and a binarization circuit 306 constituting an error detection circuit (error detection means) are provided between the connection point between the collector terminal of the light receiving element 115 and the resistor 301 and the output terminal of the error signal 1. However, an LPF 307 and a binarization circuit 308 constituting another error detection circuit are connected in series between the connection point and the output terminal of the error signal 2, respectively.

On the other hand, an anode terminal of a light emitting element (LED in this example) 111 constituting the sensor unit 201 is connected to a predetermined power source, and a cathode terminal is connected to a collector terminal of an NPN transistor 309.
The emitter terminal of the transistor 309 is grounded via the resistor 310, and the base terminal is connected to the output side of the drive circuit 311.
Further, an LPF 312 is connected between the input side of the drive circuit 311 and the connection point between the collector terminal of the light receiving element 115 and the resistor 301.

  In this mark sensor 110, an analog alternating signal (actually, a current flowing out from the emitter terminal of the light receiving element 115) output from the light receiving element 115 is converted into a voltage by the resistor 301. , Which is an analog alternating signal) is amplified by the amplifier 302 and then output to the binarization circuit 303. At this time, the output of the amplifier 302 (light receiving element 115) is stabilized by the thermistor 304. That is, the thermistor 304 performs gain adjustment (temperature correction) of the amplifier 302 so that the output from the amplifier 302 to the binarization circuit 303 does not change due to the influence of the ambient temperature. The thermistor 304 is a PTC type temperature sensor whose resistance value increases (current value decreases) as the temperature rises.

The binarizing circuit 303 is binarizing means, which converts the analog alternating signal from the amplifier 302 into a binarized signal (digital signal) as shown in FIG. Is output to the drive control apparatus 100.
The analog alternating signal output from the light receiving element 115 is also input to the LPFs 305, 307, and 312 respectively.
The LPF 305 averages the analog alternating signal (1 K to 2 KHz) output from the light receiving element 115 as shown in FIG. 8A during low-speed copying (normal copying) as shown in FIG. Smoothed) and output to the binarization circuit 306. That is, of the analog alternating signal from the light receiving element 115, only a signal having a frequency band equal to or lower than a predetermined cut-off frequency (corresponding to low-speed copying) is allowed to pass, and this is passed to the binarization circuit 306 as a filter passing signal 1. Output.

  The binarization circuit 306 has a comparator (comparison means), and has a discontinuous portion (mark break), dirt or scratches where the interval between the reflective portions (marks) 251 of the scale 250 is outside a predetermined range. It is determined from the output change of the filter pass signal 1 from the LPF 305 whether or not a mark detection impossible portion corresponding to a defective portion or the like exists in the mark detection region. That is, the comparator compares the voltage level of the filter pass signal 1 from the LPF 305 with a predetermined threshold level (reference value), so that a mark non-detectable portion exists in the mark detection region (the voltage of the filter pass signal 1). It is determined whether or not the level has become lower than a predetermined threshold level. When a mark undetectable portion exists in the mark detection area, a corresponding binary signal (low level signal) is generated as shown in FIG.

  The LPF 307 averages the analog alternating signal as shown in FIG. 9A output from the light receiving element 115 during high-speed copying, as shown by the solid line in FIG. 9B, and outputs it to the binarization circuit 308. To do. In other words, among the analog alternating signals from the light receiving element 115, only a signal having a frequency band equal to or lower than a predetermined cut-off frequency (corresponding to high-speed copying) is passed, and the signal is passed to the binarization circuit 308 as a filter passing signal 2. Output. Note that the filtered signal 1 at the time of low-speed copying shown in FIG. 8B is indicated by a broken line in FIG. 9B. From this, it can be seen that the cutoff frequencies of the LPFs 305 and 307 are different.

  The binarization circuit 308 has a comparator, and determines from the output change of the filter pass signal 2 from the LPF 307 whether or not the mark detection impossible portion exists in the mark detection region. That is, the comparator compares the voltage level of the filter pass signal 2 from the LPF 307 with a predetermined threshold level, so that a mark non-detectable portion exists in the mark detection region (the voltage level of the filter pass signal 2 is a predetermined level). It is determined whether or not it has become lower than the threshold level. When a mark undetectable portion exists in the mark detection area, a corresponding binary signal is generated as indicated by a solid line in FIG. 9C and is output as an error signal 2. Note that the error signal 1 at the time of low-speed copying shown in FIG. 8C is indicated by a broken line in FIG. 9C.

Similar to the LPF 305, the LPF 312 averages the analog alternating signal output from the light receiving element 115, and outputs it as a filter passing signal 3 to the drive circuit 311.
The drive circuit 311 functions as a light amount adjusting unit with the transistor 309, and adjusts the light amount of the light emitting element 111 by changing the amount of current to the base terminal of the transistor 309 based on the output of the LPF 312. Do.

  FIG. 10 is a circuit diagram showing a specific configuration example of the drive circuit 311 in FIG. Although not shown in FIG. 1, the connection point between the transistor 309 and the resistor 310 is connected to the input terminal (−) of the operational amplifier 407 that forms a constant current circuit together with them.

In this drive circuit 311, the comparator 401 compares the output value (voltage level) Vs of the LPF 312 with a predetermined reference value (threshold level) Vref1 and turns on or off the transistor 402 according to the comparison result. Turn off.
That is, when the relationship between the output value Vs of the LPF 312 and the reference value Vref1 is Vs> Vref1, the transistor 402 is turned on by setting the output to the transistor 402 to the high level “H”. Further, if the relationship between the output value Vs of the LPF 312 and the reference value Vref1 is Vs ≦ Vref1, the transistor 402 is turned off by setting the output to the transistor 402 to a low level “L”.

The comparator 403 compares the output value Vs of the LPF 312 with a predetermined reference value Vref2 set in advance, and turns on or off the transistor 404 according to the comparison result.
That is, if the relationship between the output value Vs of the LPF 312 and the reference value Vref2 is Vs> Vref2, the transistor 404 is turned on by setting the output to the transistor 404 to the high level “H”. If the relationship between the output value Vs of the LPF 312 and the reference value Vref2 is Vs ≦ Vref2, the transistor 404 is turned off by setting the output to the transistor 404 to a low level “L”.

A combination of outputs (output signals) of the comparators 401 and 403, that is, a combination of ON / OFF of the transistors 402 and 404, is input to the base terminal of the transistor 309 constituting the constant current circuit via the voltage follower 405 and the LPF 406. The current (base current) changes in three stages.
Here, assuming that the relationship between the reference values Vref1 and Vref2 is Vref1 <Vref2, and the relationship between the resistors R1 and R2 is R1> R2, the base currents are as shown in the following (1) to (3).
(1) When the relationship between the output value Vs of the LPF 312 and the reference values Vref1 and Vref2 is Vs ≦ Vref1 <Vref2, the outputs of the comparators 401 and 403 are both at the low level “L”. Is also turned off, and the base current (B1) at this time becomes the maximum value.

(2) When the relationship between the output value Vs of the LPF 312 and the reference values Vref1 and Vref2 is Vref1 <Vs ≦ Vref2, the output of the comparator 401 is high level “H” and the output of the comparator 403 is low level “L”. The transistor 402 is turned on, the transistor 404 is turned off, and the base current (referred to as B2) at this time has an intermediate value.
(3) When the relationship between the output value Vs of the LPF 312 and the reference values Vref1 and Vref2 is Vref1 <Vref2 <Vs, the outputs of the comparators 401 and 403 are both “H”, so that the transistors 402 and 404 are both on. In this state, the base current (referred to as B3) at this time becomes the minimum value.

That is, the relationship between the base current B1 in the case of (1), the base current B2 in the case of (2), and the base current B3 in the case of (3) is B1>B2> B3. Therefore, since the magnitude of the drive current of the light emitting element 111 proportional to the magnitude of the base current can be switched in three stages, the light amount of the light emitting element 111 can also be switched in three stages.
The LPF 406 has the same characteristics as the LPF 312. The LPF 406 can be omitted.
Here, in order to switch the voltage dividing resistor in the drive circuit 311 to three stages, two combination circuits of a comparator, a transistor, and a resistor are provided in parallel, but three or more may be provided. If it does so, it will become possible to switch the light quantity of the light emitting element 111 in four steps or more.

  On the other hand, the drive control apparatus 100 shown in FIG. 4 selects the output of the binarization circuit 306 of the mark sensor 110 at the time of low-speed copying, and based on the output, there is a mark non-detectable portion in the mark detection area. When it is recognized that there is no mark, the speed control or position control of the intermediate transfer belt 25 is performed using a control signal based on the binarized signal output from the binarizing circuit 303, and a mark non-detectable portion is detected in the mark detection area. When it is recognized that the mark detection area exists, speed control or position control different from the case where no mark detection impossible portion exists in the mark detection area is performed.

  Further, at the time of high-speed copying, if the output of the binarization circuit 308 of the mark sensor 110 is selected, and if it is recognized that there is no mark undetectable part in the mark detection area based on the output, the binary signal is output. When speed control or position control of the intermediate transfer belt 25 is performed using a control signal based on the binarized signal output from the digitizing circuit 303, and it is recognized that a mark non-detectable portion exists in the mark detection area Then, speed control or position control different from the case where no mark detection impossible portion exists in the mark detection area is performed.

In this embodiment, the LPF 312 is connected between the input side of the drive circuit 311 and the connection point between the collector terminal of the light receiving element 115 and the resistor 301. However, the LPF 305 and the high speed copy corresponding to the low speed copy. It is possible to connect two LPFs equivalent to the LPF 307 corresponding to the above in parallel.
In addition, when the color copying machine of this embodiment can switch the copy speed to three or more stages, it is preferable to provide three or more error detection circuits that are series circuits of an LPF and a binarization circuit. However, it is necessary to make the cutoff frequency of each LPF different for each copy speed. Further, an LPF equivalent to the LPF of each error detection circuit may be connected between the input side of the drive circuit 311 and the connection point between the collector terminal of the light receiving element 115 and the resistor 301.

FIG. 11 is a flowchart showing an example of speed control of the intermediate transfer belt 25 by the drive control device 100 (speed control when no mark detection impossible portion exists in the mark detection area).
When a signal for turning on the drive motor 120 is input from a main control device (a control device that comprehensively controls the entire device) (not shown), the drive control device 100 (at the drive start timing of the intermediate transfer belt 25). 11), the processing routine of FIG. 11 is started. First, in step S1, the drive motor 120 is turned on and rotated at a basic speed V (for example, corresponding to low-speed copying), which is the target speed, and in step S2, the main control device. To check whether or not a signal for turning off the drive motor 120 is input.

If a signal for turning off the drive motor 120 from the main control device is not input, a signal from the mark sensor 110 fed back in step S4 is input, and the surface of the intermediate transfer belt 25 is input from the signal. The actual speed V ′ of the (outer peripheral surface) is calculated (calculated), the basic speed V is compared with the calculated actual speed V ′ in step S5, and the basic speed V and the actual speed V ′ are determined in step S6. It is determined whether or not they are the same. If they are the same, the process returns to step S2 and the same determination and processing as described above are performed.
If the basic speed V and the actual speed V ′ are different, a speed difference V ″ (V−V ′) between the basic speed V and the actual speed V ′ is calculated in step S7, and the speed is determined in step S8. It is determined whether or not the difference V ″ is V ″> “0”.

When the speed difference V ″ is V ″> “0”, it can be determined that the actual speed V ′ is slower than the basic speed V, so the speed difference V ″ is added to the basic speed V in step S9. The rotational speed (rotational speed) of the drive motor 120 is controlled so that the speed becomes V ₁ (V + V ″), and the process returns to step S2. If the speed difference V ″ is not V ″> “0”, that is, if V ″ <“0”, it can be determined that the actual speed V ′ is faster than the basic speed V. The number of rotations of the drive motor 120 is controlled so that the speed V ₂ (V−V ″) obtained by subtracting the speed difference V ″ from V is returned to Step S2.

Therefore, correction control is performed so that the actual speed V ′ of the surface of the intermediate transfer belt 25 becomes the basic speed V by repeating the determination and processing after step S2.
Thereafter, when it is determined in step S2 that a signal for turning off the drive motor 120 is input from the main controller, the process proceeds to step S3, the drive motor 120 is turned off, and the control of FIG.

  By the way, when the drive control apparatus 100 described above recognizes that there is no mark non-detectable portion in the mark detection area, the drive control apparatus 100 performs the speed control described with reference to FIG. In the circuit configuration of the mark sensor 110 shown in FIG. 1, when it is recognized that a mark detection unusable part exists in the mark detection area by either one of the two error signals 1 or 2, the speed control described with reference to FIG. This is partly different from the control. For example, in the case of a mark non-detectable part (mark break, etc.), since that part can be recognized (detected) by inputting an error signal, the step of FIG. 11 is performed only while the error signal (low level signal) is being input. The determination and processing in S4 to S10 are prohibited, and the rotation speed of the drive motor 120 is held at the speed before the error signal is input. Or you may make it control the rotation speed of the drive motor 120 using the technique described in Japanese Patent Application No. 2003-140376 etc. which this applicant submitted previously.

FIG. 12 is a block diagram showing another configuration example of the control system of the mark sensor 110 in FIG. 4. The same parts as those in FIG.
In this mark sensor 110, the LPF 350 has functions of an LPF for error detection (error signal generation) (corresponding to the LPF 305 in FIG. 1) and an LPF for adjusting the light amount of the light emitting element 111 (corresponding to the LPF 312 in FIG. 1). It is also a thing. However, since these LPFs may have the same function, one LPF can be reduced. However, since the LPF 350 corresponds to low-speed copying, when performing high-speed copying, the LPF (corresponding to the LPF 307 in FIG. 1) and a binarization circuit (binarization circuit 308 in FIG. 1). Equivalent to the above).

In the mark sensor 110 described with reference to FIGS. 1 and 12, all or a part of the portion excluding the sensor unit 201 can be configured by an arithmetic unit such as a DSP (Digital Signal Processor).
In this embodiment, as a temperature compensation circuit for stabilizing the output of the light receiving element 115 for detecting the reflecting portion 251 (mark) of the scale 250 in the intermediate transfer belt 25, the emitter terminal of the light receiving element 115 and the resistor (fixed) Although the thermistor 304 is connected (inserted) between the connection point with the (resistor) 301 and the binarization circuit 303, any one of the following (1) to (4) may be used.

(1) The thermistor 304 is deleted, and the resistor 301 is changed to a thermistor. However, as the thermistor in that case, an NTC type whose resistance value decreases (current value increases) with increasing temperature is used.
(2) The thermistor 304 is deleted, and the resistor 310 is changed to a PTC type thermistor.
(3) The thermistor 304 is left as it is, and the resistor 310 is changed to a PTC type thermistor.
(4) The thermistor 304 is deleted, and the resistor 301 is changed to an NTC type thermistor and the resistor 310 is changed to a PTC type thermistor.

Here, when the resistor 310 is replaced with the thermistor, the current flowing through the light emitting element (LED) 111 is stabilized by the temperature correction, and the light emission amount is maintained at a constant value, and as a result, the output of the light receiving element 115 is stabilized. Will do.
Further, instead of the thermistor described above, another temperature compensation circuit having the same characteristics can be provided.
Furthermore, the amplifier 302 can be omitted, and when the thermistor 304 is not necessary, the connection point between the emitter terminal of the light receiving element 115 and the resistor 301 (or NTC type thermistor) is set in the binarization circuit 303. Connect directly to the input terminals.

  Thus, the mark sensor 110 in this color copying machine is provided with a temperature compensation circuit (thermistor) that stabilizes the output of the light receiving element 115 for detecting the mark (reflecting portion) of the scale 250 on the intermediate transfer belt 25. The analog signal output from the light receiving element 115 is averaged by the LPF 312 (which may be other averaging means), and the drive circuit 311 (light quantity adjusting means) adjusts the light quantity of the light emitting element 111 based on the output. As a result, even when the mark on the intermediate transfer belt 25 is detected by the mark sensor 110, it is possible to suppress changes in the output of the mark sensor 110 due to environmental changes such as ambient temperature changes and deterioration of the mark sensor 110 itself over time (mark The output of the sensor 110 can be stabilized regardless of environmental changes)Therefore, it is possible to prevent the edge accuracy of the mark signal (rectangular signal) from the binarization circuit 303 from being lowered.

  Each of the comparators 401 and 403 in the drive circuit 311 compares the output value of the LPF 312 with a predetermined reference value (different for each comparator), outputs a signal corresponding to the comparison result, and outputs each output signal. The constant current circuit switches the driving current of the light emitting element 111 in a stepwise manner according to the combination, whereby the light amount of the light emitting element 111 can be easily adjusted. One comparator compares the output value of the LPF 312 with a predetermined reference value and outputs a signal corresponding to the comparison result. The constant current circuit switches the drive current of the light emitting element 111 according to the output signal. You can also.

  Further, the output of the light receiving element 115 is averaged by the LPF 305 or 307, and the output value is compared with a predetermined reference value by the comparator in the binarization circuit 306 or 308, whereby the mark on the intermediate transfer belt 25 is compared. It is determined whether or not there is a mark non-detectable part in the mark detection area corresponding to a discontinuous part (mark break) whose interval is outside the predetermined range or a defective part such as dirt or scratches (mark non-detectable) Whether or not the part exists in the mark detection area is determined from the output change of the light receiving element), and when the mark undetectable part exists in the mark detection area, an error signal is output, The drive control device 100 can detect a mark non-detectable portion in the intermediate transfer belt 25. That is, the mark non-detectable portion of the intermediate transfer belt 25 can be accurately detected without using a dedicated mark and an optical sensor. Therefore, it is not necessary to use a dedicated mark and sensor for detecting the mark non-detectable portion, and low cost can be realized.

Furthermore, when copying is performed at any one of a plurality of copy speeds, an error detection circuit including an error detection LPF (LPFs 305 and 307 in this embodiment) corresponding to each of the copy speeds is provided. Even when copying is performed at a high speed, an error signal is output at an optimum timing when a mark-undetectable portion exists in the mark detection area. Therefore, the drive control device 100 on the side receiving the error signal It is possible to detect a mark non-detectable portion in the intermediate transfer belt 25. That is, it is possible to accurately detect a mark non-detectable portion on the intermediate transfer belt regardless of the copy speed without using a dedicated mark and an optical sensor.
Further, by using the LPF 350 having both the error detection LPF function and the LPF function for adjusting the light amount of the light emitting element, it is possible to realize a cheaper mark sensor.

  Further, when the drive control device 100 recognizes that there is no mark non-detectable portion in the mark detection area based on the output of the mark sensor 110, a control signal based on the mark signal (binarized signal) When the speed control or position control of the intermediate transfer belt is performed using the, and it is recognized that the mark non-detectable part exists in the mark detection area, the mark non-detectable part does not exist By performing speed control or position control different from the above, even when there is a mark non-detectable portion in the mark detection area, optimal control as speed control or position control of the intermediate transfer belt 25 can be performed.

  Therefore, in the color copying machine of this embodiment, the intermediate transfer belt 25 having the drive controller 100 and the scale 250 formed so that a plurality of marks are continuously arranged at equal intervals along the rotation direction (endless movement direction). (Endless moving member) and a drive motor 120, gears 121 and 122, and a drive roller 51 for transmitting a drive force for rotating the intermediate transfer belt 25 to the intermediate transfer belt 25, and a drive control device 100. However, since the drive control of the drive motor 120 enables accurate speed control or position control of the intermediate transfer belt 25 via the gears 121 and 122 and the drive roller 51, each color toner image on the intermediate transfer belt 25 is controlled. Can be performed with high accuracy, and the image quality can be improved.

  In the above-described embodiment, the scale 250 formed so that a plurality of marks are continuously arranged at equal intervals along the rotation direction of the intermediate transfer belt 25, and the light reflection type for detecting the presence or absence of the marks. The mark sensor 110 is used, but the scale is replaced with a hole (transmission part) such as a slit (transmission part and light-shielding part are alternately formed along the rotation direction of the intermediate transfer belt), etc. It is also possible to use a light transmission type sensor for detecting the presence or absence of the hole.

Further, the rotational direction of an endless moving member such as an endless belt member (conveying belt, transfer belt, photoconductor belt, etc.) other than the intermediate transfer belt 25 or an endless drum-like member (transfer drum, intermediate transfer drum, photoconductor drum, etc.). It is also possible to use a scale or the like in which marks or holes are formed so as to continue at regular intervals (predetermined intervals).
Furthermore, in this embodiment, the speed control or the position control of the intermediate transfer belt is performed by detecting the mark on the scale using one mark sensor. However, the mark on the scale using a plurality of mark sensors. By detecting this, it is also possible to perform speed control or position control of an endless moving member such as an intermediate transfer belt (see, for example, JP-A-9-175687). In that case, a plurality of mark sensors each having the same function as the mark sensor 110 described above may be used.

  As described above, the present invention is applied to a mark (hole) detection circuit for appropriately endlessly moving an endless moving member such as an intermediate transfer belt, a drive control device connected thereto, and a color copying machine equipped with the same. However, the present invention is not limited to this, and can be applied to various image forming apparatuses such as a printer, a facsimile machine, and a multi-function machine equipped with the drive control device.

As is apparent from the above description, according to the drive control device of the present invention, even when the mark on the endless moving member is detected by the optical sensor, the output of the optical sensor is used for the temperature change of the surroundings or the time of the optical sensor itself. It can be stabilized regardless of environmental changes such as deterioration. Further, without using a dedicated mark and optical sensor, when the mark detection disabled portion serving as outside the interval marks in endless moving member is a predetermined exists in the detection area of the optical sensor, detection knowledge it it can. Therefore , since the mark (including the mark non-detectable portion) of the endless moving member can be detected accurately and reliably, speed control or position control of the endless moving member can be appropriately performed without increasing the cost. Therefore, if this invention is utilized, the drive control apparatus which can be optimally driven at low cost can be provided.

According to the image forming apparatus of this invention, by using the above driving control device, perform appropriate image formation without cost, it is possible to improve image quality. Therefore, by using the present invention, it is possible to provide an image forming apparatus that can acquire a high-quality image at low cost.

FIG. 5 is a block diagram illustrating a configuration example of a control system (mark detection circuit) of the mark sensor 110 in FIG. 4. 1 is a configuration diagram showing an example of the internal configuration of a color copying machine as an embodiment of an image forming apparatus according to the present invention. It is a block diagram which shows the structure of the printer part 20 shown in FIG. 2 in detail. FIG. 4 is a diagram illustrating a configuration example of a belt driving device that configures the intermediate transfer belt 25 of FIG. 3 and its surrounding drive system and control system.

FIG. 5 is a configuration diagram showing an example of a scale 250 and a mark sensor (optical sensor) 110 provided on the inner peripheral surface of the intermediate transfer belt 25 shown in FIG. 4. FIG. 6 is a diagram illustrating a state in which dirt (dust) is attached to a mark detection region of the mark sensor 110 illustrated in FIG. 5. FIG. 6 is a diagram showing waveform examples of various signals when a mark is detected by the mark sensor 110 shown in FIG. 5. FIG. 6 is a diagram showing waveform examples of various signals when mark detection by the mark sensor 110 shown in FIG. 5 is impossible (corresponding to a mark detection impossible portion).

It is a diagram which shows the example of another waveform similarly. FIG. 2 is a circuit diagram illustrating a specific configuration example in a drive circuit 311 in FIG. 1. FIG. 5 is a flowchart showing an example of speed control of the intermediate transfer belt 25 by the drive control device 100 of FIG. 4. It is a block diagram which shows the other structural example of the control system of the mark sensor 110 of FIG.

Explanation of symbols

1: Copier body 20: Printer unit 25: Intermediate transfer belt 26: Photosensitive drum 51: Drive roller 53: Secondary transfer roller 54: Secondary transfer counter roller 62: Charging unit 65: Primary transfer roller 100: Drive control Device 110: Mark sensor 111: Light emitting element 112: Collimating lens 113: Slit mask 114: Glass 115: Light receiving element 120: Drive motor 121, 122: Gear 201: Sensor part 250: Scale 251: Reflecting part (mark) 301, 310 : Resistor 302: Amplifier 303, 306, 308: Binary circuit 304: Thermistor 305, 307, 312, 350, 406: LPF
309, 402, 404: Transistor 311: Drive circuit 401, 403: Comparator 405: Voltage follower

Claims (16)

A plurality of marks having a light emitting element and a light receiving element, and formed continuously at equal intervals along the direction of endless movement of the endless moving member that moves endlessly, and the movement of the endless moving member an optical science sensor continuously modulated analog signal according to the presence or absence of a mark you output from the light receiving element by,
Binarizing means for converting an analog signal output from the light receiving element into a binarized signal;
Averaging means for averaging and outputting analog signals output from the light receiving elements;
A plurality of comparing means for comparing the output values of the averaging means with different predetermined reference values ;
Control means for performing speed control or position control of the endless moving member using a control signal based on the binarized signal ;
Wherein in accordance with a combination of comparison results of the plurality of comparing means, the drive control device and switches stepwise the driving current of the light emitting element. The drive control device according to claim 1,
A drive control apparatus comprising temperature compensation means for stabilizing the output of the light receiving element. The drive control apparatus according to claim 2, wherein
The mark detection apparatus, wherein the temperature compensation means is provided on the output side of the light receiving element. The mark detection apparatus according to claim 2,
The drive control device , wherein the temperature compensation means is provided on the output side of the light amount adjustment means. The drive control apparatus according to claim 2, wherein
Said temperature compensating means, the drive control device, characterized in that the output side are provided on both the output side of said light amount adjusting means of the light receiving element. In the drive control device according to any one of claims 2 to 5,
It said temperature compensating means, the drive control device, characterized in that by using a thermistor. In the drive control device according to any one of claims 1 to 6,
It is determined from the change in the output of the analog signal whether or not a mark non-detectable portion where the mark interval is outside a predetermined range exists in the detection region of the optical sensor, and the mark non-detectable portion is the detection region A drive control device comprising error detection means for outputting an error signal when it exists in the drive control device . The drive control device according to claim 7, wherein
The error detection means includes averaging means for averaging analog signals output from the optical sensor, and the mark detection impossible portion is determined by comparing the output value of the averaging means with a predetermined reference value. A drive control device that determines whether or not the detection area of the optical sensor exists, and outputs an error signal when the mark non-detectable portion exists in the detection area. The drive control apparatus according to claim 8, wherein
The drive control apparatus characterized in that the averaging means of the error detection means is a low-pass filter. The drive control device according to claim 7, wherein
The error detection means determines whether the mark detection impossible portion exists in the detection area of the optical sensor by comparing the output value of the averaging means with a predetermined reference value, and the mark detection impossible. drive controller and outputs an error signal if the portion is present in the detection region. The drive control device according to claim 7 or 10,
Control based on the binarization signal output by the binarization unit when it is recognized that the mark non-detectable portion does not exist in the detection area of the optical sensor based on the output of the error detection unit When speed control or position control is performed using a signal and it is recognized that the mark non-detectable portion exists in the detection region of the optical sensor, the mark non-detectable portion is present in the detection region of the optical sensor. A drive control apparatus comprising speed / position control means for performing speed control or position control different from that in the case where it does not exist. The drive control apparatus according to claim 8 or 9,
A plurality of pre-Symbol error detecting means, respectively averaging means that each error detecting unit is a low-pass filter cut-off frequency is different,
A drive control device comprising: error signal selection means for selecting and outputting any one of error signals output from the plurality of error detection means according to the moving speed of the endless moving member. In the drive control apparatus according to claim 1 wherein,
Based on the binarized signal output from the binarizing means when it is recognized that the mark detection impossible portion does not exist in the detection area of the optical sensor based on the output of the error signal selecting means. When speed control or position control is performed using a control signal and it is recognized that the mark non-detectable portion exists in the detection region of the optical sensor, the mark non-detectable portion in the detection region of the optical sensor A drive control apparatus comprising speed / position control means for performing speed control or position control different from that in the case where the motor does not exist. In the drive control apparatus according to any one of claims 1乃 optimum 1 3,
The drive control device, wherein the endless moving member is a belt or a drum. And a drive control device according to any one of claims 1乃 optimum 1 3,
An endless moving member formed such that a plurality of marks continue at equal intervals along the endless moving direction;
Driving force transmitting means for transmitting a driving force for endlessly moving the endless moving member to the endless moving member;
An image forming apparatus, wherein the drive control device performs drive control of the drive force transmission means. The image forming apparatus according to claim 1 5, wherein,
An image forming apparatus, wherein the endless moving member is any one of a conveyance belt, a transfer belt, an intermediate transfer belt, a photosensitive belt, a transfer drum, an intermediate transfer drum, and a photosensitive drum.

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