JP2007101891A - Driving control apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and efficiently detect variation in rotational speed for an endless moving member. <P>SOLUTION: A driving control apparatus is provided with a density sensor 202 (composing a reflectivity detecting means) formed along the direction of periphery on an outer periphery surface of a rotating disc 201 attached to a shaft of lower right roller 66 (or any other roller) and detecting reflectivity in a density pattern with different reflectivity in positions in the direction of its periphery. The data for the reflectivity detected by the density sensor 202 during one rotation of a rotating disc 201 while keeping a constant speed are acquired for each specified time and written beforehand to memory, the data for reflectivity detected by a density sensor 202 are acquired for each specified time above when measuring (in image formation) afterward and the variation in the rotational speed is detected for the rotating disc 201 by comparing the data with the data in the memory. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotational speed fluctuation detecting device for detecting a rotational speed fluctuation of a rotating disk, a drive control device including the same, and an image forming apparatus such as a copying machine, a printer, and a facsimile machine including the same.

  In order to detect the rotational speed of the object to be rotated, the encoder disk (a disk-shaped disk having a large number of radial slit holes) and the encoder disk are opposed to each other on the same rotation axis as the object. In general, an encoder (general encoder) including a light emitter such as a light emitting diode and a light receiver such as a phototransistor is attached to detect a pulse signal corresponding to the angular velocity of the object.

In addition, a rotation angle detection device (encoder) including a disk in which slit patterns whose transmission density gradually increases or decreases according to the rotation speed is arranged on the circumference has been proposed (for example, see Patent Document 1). .
When feedback control is performed so that the rotational speed of the object to be rotationally driven is constant, the pulse signal generated by the encoder as described above is taken into the control unit, and the drive generated corresponding to the pulse signal The rotation operation may be controlled by giving a signal to the drive means of the object to be rotated.
For example, as one application example of the above technique, there is transfer drive control of a color image forming apparatus.

  As a general method of forming a color image in a color image forming apparatus, a direct transfer method in which toner images formed in different colors on a plurality of photosensitive members are transferred while being directly superimposed on a transfer sheet, and toners having the same color There is an intermediate transfer method in which an image is transferred while being superimposed on an intermediate transfer member, and then transferred onto a transfer sheet at once. These methods are commonly called a tandem method because a plurality of photosensitive members are arranged side by side facing a transfer paper or intermediate transfer member. For each photosensitive member, yellow (Y), magenta (M), cyan (C ), An electrophotographic process such as formation and development of an electrostatic latent image is executed for each color of black (K), and on the transfer paper in the direct transfer method, the intermediate transfer in the intermediate transfer method Transfer on the body.

  In a tandem color image forming apparatus using each of these methods, an endless belt (endless belt) that runs while supporting transfer paper is used in the direct transfer method, and a photoconductor in the intermediate transfer method. It is common to employ an endless belt that receives and carries an image. Image forming units each including four photoconductors are arranged side by side along one running side of the endless belt.

  In the tandem color image forming apparatus, it is important to prevent the occurrence of color misregistration by accurately superimposing the toner images of the respective colors. Therefore, in any transfer system, an encoder is attached to one of the plurality of driven shafts constituting the transfer unit in order to avoid color misregistration due to the speed fluctuation of the transfer belt, and according to the rotational speed fluctuation of the encoder. Thus, feedback control of the rotational speed of the drive roller is an effective means.

  The most common method for realizing such feedback control is proportional control (PI control). First, the position deviation e (n) is calculated from the difference between the target angular displacement Ref (n) of the encoder and the detected angular displacement P (n-1) of the encoder. Then, a low-pass filter is applied to the position deviation e (n) of the calculation result to remove high frequency noise, a control gain is applied, and a certain standard drive pulse frequency is added. By controlling the drive motor that drives the drive roller based on the obtained drive pulse frequency, the encoder output can be controlled to always be driven at the target angular displacement.

As actual control, a counter that counts the rising edge of the output of the encoder pulse and a counter that counts every control cycle (for example, 1 ms) are used, and the calculation result of the target angular displacement that moves during the control cycle (1 ms) The position deviation can be acquired from the difference from the detected angular displacement obtained by acquiring the encoder count value for each control cycle.
A specific calculation is as follows when the roller diameter of the driven shaft to which the encoder is attached is φ15.615.

e (n) = θ0 × q−θ1 × ne [rad]
The meaning of each symbol in this formula is as follows.
e (n) [rad]: Position deviation calculated in the current sampling θ0 [rad]: Movement angle per control cycle (= 2π × V × 10 ⁻³ /15.615π [rad])
θ1 [rad]: Movement angle per pulse of encoder (= 2π / p [rad], where p is the slit pitch of the encoder)
q: Count value of control cycle timer ne: Encoder count value V: Belt linear velocity [mm / s]

Here, for example, assuming that the encoder has a control period of 1 ms and the resolution of the encoder is 300 pulses per revolution, and the feedback control is performed so that the transfer belt operates at 162 mm / s, the following is assumed.
θ0 = 2π × 162 × 10 ⁻³ /15.615π=0.0207487 [rad]
θ1 = 2π × p = 2π / 300 = 0.0209439 [rad]
A position deviation is acquired by performing the above calculation for every control period, and feedback control is performed.

  The structure of a general encoder is as described above. The encoder disk is press-fitted into the driven roller shaft, and the encoder disk and the driven roller are mounted so as to rotate simultaneously. By detecting the slit on the encoder disk with a sensor, a pulse signal corresponding to the amount of rotation of the driven roller can be obtained. The rotational speed of the driving roller is controlled by detecting the moving angle of the driven roller using this pulse signal.

  However, due to the influence of the concentricity processing accuracy of the encoder disk, when the encoder disk is attached to the driven roller, it may be attached in a state shifted from each other. When rotating in this state, the encoder roller is rotated in an eccentric state even though the driven roller is rotating at a constant speed. When this is read by the light receiver, one rotation component of the encoder disk is output to the output of the light receiver, that is, the pulse signal. Further, since one rotation component is amplified by feedback control to rotate the driving roller, the transfer belt speed fluctuates every rotation of the encoder disk, and color misregistration occurs.

Originally, in feedback control, we would like to improve the response to load fluctuations by increasing the control gain. However, if the control gain is increased, one rotation component of the disk increases, resulting in increased color misregistration. Had to perform feedback control with a low control gain. For this reason, the removal of other variable components that are originally desired to be controlled has not been sufficiently performed.
Such a problem also occurs in the rotation angle detection device (encoder) described in Patent Document 1.

Therefore, an image carrier such as a photosensitive member is exposed at a time interval required for the image carrier to rotate by 1 / n (n: integer) of the circumferential length to form a pattern, and the pattern is read. A color image forming apparatus has also been proposed in which periodic rotation speed fluctuation data of an image carrier is created by processing with a shape filter, and the rotation speed of the image carrier is controlled by an antiphase component of the rotation speed fluctuation data. (For example, refer to Patent Document 2).
Japanese Patent Laid-Open No. 10-111147 JP 2003-66660 A

  However, in the color image forming apparatus described in Patent Document 2, in order to control the rotation speed of the image carrier, a pattern as described above is formed on the image carrier and read to create rotation variation data. Therefore, it takes a long time to complete the original image forming process, and there is a problem that the throughput of image formation is reduced.

  The present invention has been made to solve such a problem, and it is possible to reduce the rotational speed fluctuation of an endless moving member (such as an endless belt member) of a drive control device provided in an electronic apparatus such as an image forming apparatus. The object is to enable accurate and efficient detection.

In order to achieve the above object, the present invention provides a rotational speed fluctuation detecting device, a drive control device, and an image forming apparatus having the same.
A rotational speed fluctuation detecting apparatus according to a first aspect of the present invention is a rotational speed fluctuation detecting apparatus for detecting a rotational speed fluctuation of a rotary disk, wherein the rotary disk has a pattern in which a reflectance varies depending on a circumferential position of an outer peripheral surface thereof. Is formed along the circumferential direction, and the reflectance detection means for detecting the reflectance of the pattern and the reflection detected by the reflectance detection means in advance during one rotation of the rotating disk at a constant speed. Data acquisition means for acquiring rate data every predetermined time and writing it into the memory, and reflectance data detected by the reflectance detection means during measurement at every predetermined time and comparing with the data in the memory Thus, there is provided a fluctuation detecting means for detecting fluctuations in the rotational speed of the rotating disk.

  According to a second aspect of the present invention, there is provided a rotational speed fluctuation detecting apparatus for detecting a rotational speed fluctuation of a rotating disk, wherein the rotating disk has a pattern in which the reflectance varies depending on a circumferential position of an outer peripheral surface thereof. Is formed along the circumferential direction, and the reflectance detection means for detecting the reflectance of the pattern and the reflection detected by the reflectance detection means during one rotation of the rotating disk at a constant speed in advance. The data acquisition means for acquiring and storing the rate data every predetermined time, and writing the difference data between the reflectivity data stored last time and the reflectivity data stored this time in the memory, and the reflectivity at the time of measurement The reflectance data detected by the detecting means is acquired and stored every predetermined time, and each time the reflectance data stored last time and the reflectance data stored this time are stored. The difference data is provided with a a variation detecting means for detecting a rotational speed variation of the rotating disk by comparing the difference data in the memory.

According to a third aspect of the present invention, in the rotational speed fluctuation detecting device according to the first or second aspect, the pattern is constituted by a plurality of marks each having a different reflectance.
A drive control apparatus according to a fourth aspect of the present invention is a drive control apparatus comprising the rotational speed variation detection apparatus according to any one of the first to third aspects, wherein the drive disk rotates an endless moving member on the rotary disk or A driven roller that is driven and rotated by rotation of the endless moving member is attached, and the drive is driven based on a drive source that rotates the drive roller, and a rotational speed fluctuation of the rotary disk detected by the rotational speed fluctuation detecting device. And a control means for driving and controlling the source.

An image forming apparatus according to a fifth aspect of the present invention includes the drive control apparatus according to the fourth aspect, wherein the endless moving member is an endless moving member for image formation.
An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, wherein the endless moving member for image formation is a photosensitive belt, a transfer belt, an intermediate transfer belt, or an image recording medium conveying belt. One or more of the above.

  According to the rotational speed fluctuation detecting device of the present invention, the reflectance for detecting the reflectance of the pattern of the rotating disk (a pattern in which the reflectance varies depending on the position of the outer circumferential surface in the circumferential direction). A detecting unit is provided, and reflectance data detected by the reflectance detecting unit is acquired every predetermined time while the rotating disk rotates once at a constant speed (for example, when image formation is not being performed) and is stored in a memory. Reflection data detected by the reflectance detection means at the time of writing and subsequent measurement is obtained every predetermined time, and the rotational speed fluctuation of the rotating disk is detected by comparing with the data in the memory. Drive roller or endless for rotating an endless moving member (such as an endless belt member) of a drive control device provided in an electronic apparatus such as an image forming apparatus on a disk By mounting the driven roller is driven to rotate by the rotation of the rotary members, the rotational speed fluctuation of the endless moving member can be accurately and efficiently detected.

Alternatively, the reflectance data detected by the reflectance detection means is acquired and stored every predetermined time while the rotating disk rotates once at a constant speed, and the previously stored reflectance data and this time are stored each time. The difference data with the reflectivity data is written into the memory, and the reflectivity data detected by the reflectivity detecting means during subsequent measurement is acquired and stored at the predetermined time, and the reflectivity previously stored each time. By detecting the rotational speed fluctuation of the rotating disk by comparing the difference data between the data of the above and the reflectance data stored this time with the difference data in the memory, an electronic device such as an image forming apparatus is also provided on the rotating disk. A drive roller for rotating the endless moving member of the drive control device provided in the apparatus or a driven roller that rotates following the rotation of the endless moving member is attached. More, the rotational speed fluctuation of the endless moving member can be accurately and efficiently detected.
According to the image forming apparatus provided with the drive control device of the present invention, it is possible to perform appropriate image formation and improve image quality.

Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
First, referring to FIG. 2 and FIG. 3, a configuration example of an image forming apparatus provided with a drive control device having a rotational speed fluctuation detecting device according to the present invention will be described. This image forming apparatus is a color laser printer (hereinafter referred to as “laser printer”) that forms a color image by a direct transfer type electrophotographic method, and FIG. 2 is a schematic configuration diagram of the entire laser printer.

As shown in FIG. 2, the laser printer includes four sets of toner image forming units 1 (1Y) for forming images of each color of Y (yellow), M (magenta), C (cyan), and K (black). , 1M, 1C, 1K) are arranged in order from the upstream side (lower right side in the figure) in the direction in which the transfer paper P moves as the transfer conveyance belt 60 travels along the arrow A in the figure.
Each toner image forming unit 1 includes a photosensitive drum 11 (11Y, 11M, 11C, 11K) as an image carrier and a developing unit 12. The arrangement of the toner image forming units 1 is set so that the rotation axes of the photosensitive drums 11 are parallel to each other and arranged at a predetermined pitch in the transfer paper moving direction.

  In addition to the toner image forming unit 1, this laser printer carries an optical writing unit 2, paper feed cassettes 3 and 4, a registration roller pair 5, and a transfer paper (image recording medium) P to form each toner image. Belt driving device 6 equipped with a transfer conveyance belt (which combines the functions of a transfer belt and an image recording medium conveyance belt) 60 as an endless moving member that conveys the paper so as to pass through the transfer position of the belt, belt fixing type fixing A unit 7 and a paper discharge tray 8 are provided. The belt driving device 6 is a combination of a control system (a driving control device having a rotational speed fluctuation detecting device) described later, and also functions as a transfer unit.

The laser printer further includes a manual feed tray 14 and a toner replenishing container 22, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like (not shown) are also provided in a space S indicated by a two-dot chain line.
The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface (outer peripheral surface) of each photosensitive drum 11 while scanning with laser light based on image data. .

FIG. 3 is an enlarged view showing a schematic configuration of the belt driving device 6 described above.
The transfer conveying belt 60 used in the belt driving device 6 is a high-resistance endless single-layer endless belt (endless belt member) having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and the material thereof is, for example, PVDF (Polyvinylidene fluoride). The transfer conveyance belt 60 is stretched around support rollers 61 to 66 so as to pass through the transfer positions that are in contact with and face the photosensitive drum 11 of the toner image forming units 1.

  An electrostatic attraction roller 80 is provided so as to face the entrance roller 61 located upstream of the support rollers 61 to 66 in the transfer paper moving direction on the outer peripheral surface side of the transfer conveyance belt 60. Yes. A predetermined voltage is applied to the electrostatic attraction roller 80 by the power supply 18, and the transfer paper P that has passed between the two rollers 61 and 80 is charged and electrostatically adsorbed onto the transfer conveyance belt 60. A drive roller 63 frictionally drives the transfer conveyance belt 60 and is rotated in the direction of arrow D by a drive motor (described later) as a drive source.

  The transfer bias applying member 27 (27Y, 27M, 27C, 27K) as transfer electric field forming means for forming a transfer electric field is brought into contact with the back surface of the transfer conveyance belt 60 at each transfer position facing each photoconductor drum 11. Is provided. These transfer bias applying members 27 are bias rollers provided with a sponge or the like on the outer periphery, and a transfer bias voltage is applied to the roller core from each transfer bias power source 9 (9Y, 9M, 9C, 9K). By the action of the applied transfer bias voltage, a transfer charge is applied to the transfer conveyance belt 60, and a transfer electric field having a predetermined intensity is generated between the surface of the transfer conveyance belt 60 and the surface of the photosensitive drum 11 at each transfer position. It is formed. In addition, a backup roller 68 is provided in order to keep the contact between the transfer paper and the photosensitive drum 11 in an area where the transfer is performed, and to obtain the best transfer nip.

  Each transfer bias applying member 27 and the backup roller 68 disposed in the vicinity thereof are respectively integrally held by a swing bracket 93 so as to be rotatable, and can be rotated around a rotation shaft 94. This rotation is clockwise when the cam 96 fixed to the cam shaft 97 is rotated in the direction of arrow E.

  The entrance roller 61 and the electrostatic attraction roller 80 described above are integrally supported by the entrance roller bracket 90, and can be rotated clockwise from the state of FIG. A pin 92 projecting from the entrance roller bracket 90 is fitted into a hole 95 provided in the swing bracket 93, and the entrance roller bracket 90 also rotates in conjunction with the rotation of the swing bracket 93. . By rotating the brackets 90 and 93 in the clockwise direction, the respective transfer bias applying members 27 and the backup rollers 68 disposed in the vicinity thereof are separated from the photosensitive drum 11, and the entrance roller 61 and the electrostatic adsorption roller 80. Also move downwards. This makes it possible to avoid contact between the photosensitive drums 11Y, 11M, and 11C and the transfer conveyance belt 60 when an image is formed using only black toner.

  On the other hand, the transfer bias applying member 27K and the backup roller 68 adjacent to the transfer bias applying member 27K are rotatably supported by the outlet bracket 98, and are rotatable about a shaft 99 coaxial with the outlet roller 62. When the belt driving device 6 is attached to or detached from the laser printer main body, the exit bracket 98 is rotated clockwise by the operation of a handle (not shown), and the transfer conveying belt 60 is moved together with the transfer bias applying member 27K and the backup roller 68. It can be separated from the photosensitive drum 11K for black image formation.

As shown in FIG. 2, a cleaning device 85 including a brush roller and a cleaning blade is disposed on the outer peripheral surface of the portion of the transfer conveyance belt 60 wound around the driving roller 63. The cleaning device 85 removes foreign matters such as residual toner adhering to the transfer / conveying belt 60.
A roller 64 is provided so as to push the outer peripheral surface of the transfer conveyance belt 60 immediately downstream of the drive roller 63 in the traveling direction of the transfer conveyance belt 60, and a large winding angle of the transfer conveyance belt 60 with respect to the drive roller 63 is ensured. Yes. A tension roller 65 that is in contact with the inner peripheral surface of the transfer conveyance belt 60 and is pressed outward by the biasing force of a spring 69 that is a pressing member to apply tension to the transfer conveyance belt 60 is provided immediately downstream of the roller 64. It is arranged.

Next, an image forming operation by this laser printer will be described.
At the time of image formation by this laser printer, the transfer paper P is fed from one of the paper feed cassettes 3 and 4 and the manual feed tray 14 shown in FIG. 2, and is guided to a conveyance guide (not shown) along a conveyance path indicated by a one-dot chain line. And is conveyed to a temporary stop position where the registration roller pair 5 is provided.

  On the other hand, at the time of color image formation, the photosensitive drums 11 (11Y, 11M, 11C, 11K) of the four sets of toner image forming units 1 (1Y, 1M, 1C, 1K) are rotated clockwise in FIG. After the surface is uniformly charged by a charging member (not shown), the optical writing unit 2 irradiates and scans the surface with laser light modulated by data of each color of the image to be formed, A latent image is written. Thereafter, the toner is developed with toner of each color by the developing unit, and a toner image of each color is formed on the surface of each photoconductive drum 11.

The transfer paper P sandwiched between the registration roller pair 5 and temporarily stopped as described above is sent out at a predetermined timing by the registration roller pair 5 and is carried on the transfer conveyance belt 60 toward each toner image forming unit 1. It is sequentially conveyed and passes through each transfer nip. The toner images of the respective colors formed on the photosensitive drums 11 of the respective toner image forming units 1 are formed at sequentially shifted image forming timings so as to be superimposed on the transfer paper P at the respective transfer nips. When the transfer paper P passes through each transfer nip, it is transferred onto the transfer paper P under the action of the transfer electric field and nip pressure. A full color toner image is formed on the transfer paper P by this superposition transfer.
The surface of each photosensitive drum 11 after the toner image transfer is cleaned by a cleaning device 13 and is further discharged to prepare for the formation of the next electrostatic latent image.

  On the other hand, the transfer paper P on which the full-color toner image is formed is fixed in the first paper discharge direction B or the second in accordance with the rotation posture of the switching guide 21 after the full-color toner image is fixed by the fixing unit 7. In the paper discharge direction C. When the paper is discharged from the first paper discharge direction B onto the paper discharge tray 8, it is stacked in a so-called face-down state with the image surface down. On the other hand, when the paper is discharged in the second paper discharge direction C, it is conveyed toward another post-processing device (not shown) (such as a sorter or a binding device) or printed on both sides via a switchback unit. It is again conveyed to the registration roller pair 5.

As described above, this laser printer forms a full-color image on the transfer paper P.
In such a tandem image forming apparatus, it is important to prevent the occurrence of color misregistration by superimposing toner images of respective colors with high positional accuracy. However, the driving roller 63, the entrance roller 61, the exit roller 62, and the transfer / conveying belt 60 used in the belt driving device 6 cause a manufacturing error of several tens of μm at the time of manufacturing the parts. Due to this error, a fluctuation component generated when each part makes one rotation is transmitted to the transfer conveyance belt 60, and the transfer speed of the transfer paper varies.

Due to the change in the transfer paper conveyance speed (the rotation speed of the transfer conveyance belt 60), when the toner image on each photoconductive drum 11 is transferred to the transfer paper P, a subtle shift occurs in the timing. Color misregistration occurs in the direction (transfer paper transport direction). In particular, in an apparatus that forms an image with minute dots such as 1200 × 1200 DPI, a deviation in timing of several μm is conspicuous as a color deviation.
Therefore, in order to solve the problem, the belt driving device 6 (drive control device) in this embodiment is provided with means related to the present invention described later.
Here, before describing the means, conventional means to be compared will be described.

  In the conventional means, the rotational speed of the lower right roller 66 is detected by a detection signal of an encoder (general encoder) provided on the shaft of the driven roller (hereinafter referred to as “lower right roller”) 66 in the lower right in FIG. The transfer conveyance belt 60 is caused to travel at a constant speed by feedback controlling the rotation of the drive roller 63.

FIG. 4 is a perspective view showing the overall configuration of the belt driving device 6 through the transfer conveyance belt 60 relating to the conventional means. For convenience of explanation, the same reference numerals as in this embodiment are used.
The drive roller 63 is connected to the drive motor 32 via the timing belt 33 and is driven to rotate in proportion to the rotational speed of the drive motor 32. Then, the transfer conveying belt 60 is frictionally driven by the rotation of the driving roller 63, and the lower right roller 66 is frictionally rotated by driving the transfer conveying belt 60. An encoder 31 is provided on the shaft of the lower right roller 66, and the speed control of the drive motor 32 is performed based on the rotational speed of the lower right roller 66 detected from the encoder 31. As described above, this is performed in order to suppress color misregistration due to positional variation (rotational variation) of the transfer conveyance belt 60.

FIG. 5 shows details of the lower right roller 66 and the encoder 31. The encoder 31 includes a rotating disk 311, a light emitting element 312, a light receiving element 313, and press-fit bushings 314 and 315. The rotary disk 311 is fixed by press-fitting press-fitting bushes 314 and 315 to the shaft of the lower right roller 66, and rotates simultaneously with the rotation of the lower right roller 66.
The rotating disk 311 is formed with radial slits that transmit light with a resolution of several hundred units in the circumferential direction, and light emitting elements 312 and light receiving elements 313 are arranged on both sides thereof. The light receiving element 313 generates a number of pulse signals corresponding to the rotation angle of the lower right roller 66. The movement angle (angular displacement) of the lower right roller 66 is detected using the pulse signal, and the drive amount of the drive motor 32 is controlled.

  However, for example, as shown in FIG. 6, an error of several μm occurs in the machining of the coaxial hole when the rotary disk 311 is press-fitted into the lower right roller 66, and it is practically impossible to make this zero. It is. Therefore, when the rotating disk 311 is attached to the lower right roller 66, it may be attached in a state shifted from each other. When rotating in this state, the lower right roller 66 rotates at a constant speed. The rotating disk 311 is rotated in an eccentric state. When this is read by the light receiving element 313, an angular displacement fluctuation occurs every cycle of the rotating disk 311.

FIG. 7 shows a sampling result when the drive motor 32 is driven at a constant speed and the count value of the output pulse of the encoder 31 is sampled at a constant timing.
In FIG. 7, (a) shows the sampling result when the rotating disk 311 is not eccentric, and (b) shows the sampling result when there is eccentricity. Usually, when there is no eccentricity of the rotating disk 311, a sampling result that rises to the right is obtained, but when there is eccentricity, a sine wave sampling result is obtained. Since the sampling result indicates the detected angular displacement of the encoder 31, the fact that the sampling result is a sine wave indicates that the detected position error is large accordingly. When the machining accuracy error of the coaxial hole of the rotating disk 311 is large, the amplitude of this sine wave is detected to be larger.

  In the proportional control calculation, as described above, a control gain is applied to the difference between the target angular displacement and the detected angular displacement for each control cycle to control the drive speed of the drive motor 32. Therefore, the detected angular displacement error due to the eccentricity of the rotating disk 311 is performed. If it is large, the drive motor 32 is driven with higher amplification. For this reason, position fluctuations of the transfer / conveying belt 60 occur every cycle of the rotating disk 311, and color misregistration occurs.

  Therefore, in order to solve the problem, the belt driving device 6 (including the drive control device) in this embodiment is provided with means according to the present invention. Thereby, in order to remove the angular displacement fluctuation caused by the eccentricity due to the machining accuracy error of the coaxial hole of the rotating disk 311 generated when the encoder 31 is used, the drive roller 63 and the entrance roller are not used without using the encoder 31. 61, an exit roller 62, or a density pattern formed on the outer peripheral surface of a rotating disk attached to the shaft of the lower right roller 66, etc., with respect to a transfer position variation of the transfer transport belt 60 due to a manufacturing error in manufacturing parts of the transfer transport belt 60. The transfer / conveyance belt 60 is allowed to travel at a constant speed by detecting the reflectance (detection) and controlling the feedback of the rotation of the drive roller 63.

FIG. 1 is a perspective view showing a first example of the main configuration of the belt driving device 6 (configuration of the variation detection mechanism of the transfer conveyance belt 60) when the target roller is the lower right roller 66. FIG.
In this belt driving device 6, the rotating disk 201 is attached to the lower right roller 66, and the outer circumferential surface (side surface) of the rotating disk 201 has a uniform density (reflectance) in the thickness direction, and the circumferential direction (rotating direction) ) Is formed with a density pattern having a different reflectance (density) depending on the position.
The density sensor 202 is a sensor for detecting the reflectance of the density pattern formed on the outer peripheral surface of the rotating disk 201, and is disposed so as to face the portion where the density pattern is formed.

The density sensor 202 includes a light irradiation part (LED, etc.) and a light detection part (photodiode, phototransistor, etc.), and irradiates light from the light irradiation part and is formed on the outer peripheral surface of the rotating disk 201. The light reflected by the density pattern is received by the light detection unit, and an analog potential corresponding to the received light amount is output.
The rotating disk 201 is fixed by press-fitting press-fitting bushes 314 and 315 on the shaft of the lower right roller 66, and rotates simultaneously with the rotation of the lower right roller 66.
Therefore, the density potential (reflectance) of the density pattern on the outer peripheral surface of the rotating disk 201 corresponding to the rotation angle of the lower right roller 66 is detected by the density sensor 202, so that the analog potential corresponding to the rotation angle of the lower right roller 66 is obtained. Can be obtained.
The rotating disk 201 is not limited to the lower right roller 66 but may be attached to at least one roller (target roller) of the drive roller 63, the entrance roller 61, and the exit roller 62.

FIG. 8 is a block diagram illustrating a hardware configuration example of a control unit including a drive motor control unit (drive control device) of the belt drive device 6 in the laser printer.
The drive motor controller of the belt driving device 6 converts the analog potential output from the density sensor 202 into a digital value (reflectance data), and digitally controls the drive pulse of the drive motor 32 based on the digital value (feedback). control).

The control unit 100 including the drive motor control unit includes a CPU 101, a RAM 102, a ROM 103, an I / O control unit 104, a drive motor I / F 106, a driver 107, a reflectance detection unit 108, a CPU bus 109, a timer 110, and an EEPROM 111. It is configured.
The reflectance detection unit 108 includes an IV conversion unit 112, an LPF 113, and an ADC 114.

The CPU 101 controls the entire laser printer based on the program stored in the ROM 103, including the reception of image data from the external device 120 such as a personal computer and the control of transmission / reception of control commands to / from the external device 120. Central processing unit.
In addition to the reflectance detection unit 108, a RAM 102, a ROM 103, and an I / O control unit 104 are connected to the CPU 101 via a CPU bus 109. A drive motor I / F 106 is connected via a CPU bus 109 and an I / O control unit 104.

A RAM 102 is a readable / writable memory used as a work memory when the CPU 101 performs control (processing) and an image memory when developing image data.
The ROM 103 is a read-only memory that stores fixed data such as a program executed by the CPU 101 (for the CPU 101 to operate).
The EEPROM 111 is a nonvolatile memory for storing various data (information).
The I / O control unit 104 controls each load 121 such as a motor, a clutch, a solenoid, and a sensor according to an instruction from the CPU 101.

  When the drive motor I / F 106 receives a drive command from the CPU 101 via the CPU bus 109 and the I / O control unit 104, the drive motor I / F 106 transmits power semiconductor elements to the drive motor 32 (drive roller 63) for rotating the transfer conveyance belt 60. The rotation drive of the drive motor 32 is controlled by outputting a drive pulse signal via a driver 107 composed of (for example, a transistor). Since this rotation driving is performed according to the frequency of the drive pulse signal, the rotation speed of the transfer conveyance belt 60 can be variably controlled.

The analog potential (analog signal) of the density sensor 202 is input to the reflectance detection unit 108. In the reflectance detection unit 108, the analog potential of the density sensor 202 is subjected to current-voltage conversion by the IV conversion unit 112, high frequency noise is removed by the LPF (low pass filter) 113, and then input to the ADC 114. The ADC (A / D converter) 114 converts the output value of the LPF 113 (corresponding to the analog potential of the density sensor 202) into a digital value.
The timer 110 is a periodic timer, which is activated by an instruction (repeatedly performed) from the CPU 101 (starts time measurement from “0”), and is sent to the CPU 101 at a predetermined timing (when a preset predetermined time is reached). An interrupt is generated.

Here, when receiving an interrupt from the timer 110, the CPU 101 executes access to the reflectance detection unit 108. Since the CPU 101 and the reflectance detection unit 108 are connected via the CPU bus 109, when the CPU 101 executes read access to the reflectance detection unit 108, the reflectance detection unit 108 outputs the output value (analogue) of the density sensor 202. Potential) is converted into a digital value as described above and output onto the CPU bus 109.
The CPU 101 acquires a digital value (an output value of the reflectance detection unit 108) corresponding to the output value of the density sensor 202 by read access (read processing) to the reflectance detection unit 108.

In this way, the CPU 101 can acquire a digital value corresponding to the output value of the density sensor 202 every predetermined time set in the timer 110.
The CPU 101 operates in accordance with a program in the ROM 103, and uses the density sensor 202, the reflectance detection unit 108, the timer 110, etc. as necessary, so that each means according to the present invention, that is, the reflectance detection means and the data acquisition means. , And a function as a fluctuation detecting means.

  In the following, embodiments of the laser printer relating to the present invention (control according to the present invention by the CPU 101 of the control unit 100) will be described with reference to FIGS. For convenience of explanation, the lower right roller 66 is a target roller (a roller used to detect fluctuations in the rotation speed of the transfer conveyance belt 60), but other rollers (a driving roller 63, a lower right roller 66). , Any one of the entrance roller 61 and the exit roller 62) may be the target roller.

[First embodiment]
First, the first embodiment will be described.
The CPU 101 first performs preprocessing.
That is, the drive motor 32 is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates. Reflected light from the density pattern formed on the outer peripheral surface (side surface) of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 as an analog potential while sequentially changing.

Then, the transfer conveyance belt 60 is driven at a constant speed (predetermined speed), and a digital value (data on the rotating disk 201) corresponding to the output value of the density sensor 202 is timered while the rotating disk 201 makes one rotation (one turn). 110 is acquired every predetermined time (every time an interrupt from the timer 110 is received), and written into the RAM 102. When the data for one rotation of the rotating disk 201 is prepared, the data is transferred to the EEPROM 111 and written and stored (held).
Since the above-described preprocessing is performed when the above-described image forming process (image formation) is not performed, it may be performed once at the time of factory shipment. Alternatively, if it is executed every time the power is turned on or the drive motor 32 is driven (however, the image forming process is not performed), data for one rotation of the rotating disk 201 is acquired in the RAM 102 and then transferred to the EEPROM 111. There is no need.

Control relating to detection of fluctuations in the rotational speed of the rotating disk 201 (lower right roller 66) is performed as follows.
During the image forming process, the CPU 101 drives the drive motor 32 via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotating disk 201 attached to the shaft of the lower right roller 66 rotates. The reflected light from the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 while changing sequentially.

Each time the CPU 101 receives an interrupt from the timer 110, the CPU 101 acquires a digital value (data) corresponding to the output value of the density sensor 202 from the reflectance detection unit 108. At this time, the data for one rotation of the rotating disk 201 obtained by the pre-processing and stored in the EEPROM 111 is compared as needed to detect the rotational speed fluctuation of the rotating disk 201, that is, the rotational speed fluctuation of the transfer conveyance belt 60. To do.
When the above preprocessing is performed at the time of shipment from the factory, data for one rotation of the rotating disk 201 stored in the EEPROM 111 is expanded in the RAM 102 when the power is turned on.

By the way, in the same way as the error that can occur in the processing of the coaxial hole when the rotary disk 311 of the encoder 31 is press-fitted into the lower right roller 66, the number of operations in the coaxial hole when the rotary disk 201 is press-fitted into the lower right roller 66 is several. An error of μm is inevitable.
In the conventional method, when the rotating disk 311 is attached to the lower right roller 66, the rotating disk 311 may be attached so as to be shifted from each other. If the rotating disk 311 is rotated in this state, the lower right roller 66 rotates at a constant speed. Regardless, if the rotating disk 311 is rotated in an eccentric state and is read by the light receiving element 313, there is a problem that angular displacement fluctuations occur in every cycle of the rotating disk 311.

  In the first embodiment, the density pattern formed on the outer peripheral surface (side surface) of the rotating disk 201 is detected by the reflective density sensor 202. The concentricity processing accuracy between the rotating disk 201 and the lower right roller 66 is affected by the distance between the upper surface of the density pattern formed on the outer peripheral surface of the rotating disk 201 and the density sensor 202, but the fluctuation is in units of several μm. There is no problem in actual use.

  As described above, the first embodiment includes the driving roller 63 that rotates the transfer conveyance belt 60, and the lower right roller 66 that is driven to rotate by the rotation of the transfer conveyance belt 60, the entrance roller 61, and the exit roller 62. The rotating disk 201 attached to the shaft of the lower right roller 66 (which may be the driving roller 63, the inlet roller 61, or the outlet roller 62) and the density pattern formed on the outer peripheral surface thereof (the density depends on the rotation angle of the rotating disk 201). A density sensor 202 for detecting the reflectance of the sensor 202 (differing in the reflectance detected by the sensor 202), a timer 110 for measuring time, and an EEPROM 111 (or RAM 102) for holding data, and a rotating disk 201 Is rotating at a constant speed (when the image forming process is not being performed) (Tal value) is acquired by the density sensor 202 every time the measurement time by the timer 110 reaches a predetermined time (every predetermined time), and data for one rotation of the rotating disk 201 is held in the EEPROM 111 in advance, Even during the image process, the rotational speed fluctuation of the rotating disk 201 is detected by acquiring the data of the rotating disk 201 by the density sensor 202 every predetermined time and comparing it with the data held in the EEPROM 111.

  According to the first embodiment, in order to remove the angular displacement fluctuation caused by the eccentricity due to the machining accuracy error of the coaxial hole of the encoder disk (rotating disk) generated when a general encoder is used, The transfer position fluctuation (rotation) of the transfer conveyance belt 60 due to manufacturing errors in manufacturing parts of the drive roller 63, the entrance roller 61, the exit roller 62, and the transfer conveyance belt 60 used in the belt driving device 6 without using an encoder. Speed fluctuation) can be reliably and efficiently detected by detecting the density (reflectance) of the density pattern on the outer peripheral surface of the rotating disk 201 attached to the shaft of the target roller such as the lower right roller 66. Therefore, it is possible to easily avoid the color shift of the color image formed on the transfer paper.

[Second Embodiment]
Next, a second embodiment will be described.
The CPU 101 first performs preprocessing.
That is, the drive motor 32 is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotating disk 201 attached to the shaft of the lower right roller 66 rotates. The reflected light from the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 as an analog potential while sequentially changing.

Then, the transfer conveyance belt 60 is driven at a constant speed, and a digital value (data on the rotating disk 201) corresponding to the output value of the density sensor 202 is rotated at predetermined intervals using the timer 110 while the rotating disk 201 rotates once. get. At this time, at least two digital values to be compared are stored in the memory in the CPU 101 or the RAM 102 so that the digital value acquired this time can be compared with the digital value acquired last time. Since this is the same in the embodiments described later, the description thereof will be omitted.
Next, the digital value (digital value acquired after the second time) corresponding to the output value of the density sensor 202 acquired this time is the immediately preceding (previously acquired) digital value (initially the initial digital value acquired first time). And the difference is calculated, and the difference data is written in the RAM 102. When the difference data for one rotation of the rotating disk 201 is prepared, the difference data is transferred to the EEPROM 111 (or RAM 102), written and stored.

Control relating to detection of fluctuations in the rotational speed of the rotating disk 201 (lower right roller 66) is performed as follows.
During the image forming process, the CPU 101 drives the drive motor 32 via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates. The reflected light from the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 while changing sequentially.

Each time the CPU 101 receives an interrupt from the timer 110, the CPU 101 acquires a digital value (data) corresponding to the output value of the density sensor 202 from the reflectance detection unit 108. Also at this time, at least two digital values to be compared are stored in the memory in the CPU 101 or the RAM 102 so that the digital value acquired this time can be compared with the digital value acquired last time. Since this is the same in the embodiments described later, the description thereof will be omitted.
Next, a difference is calculated by comparing the digital value acquired this time (digital value acquired after the second time) with the immediately preceding digital value (initially the initial digital value acquired for the first time), and the difference data is Comparison with the difference data acquired by the processing and stored in the EEPROM 111 is performed as needed to detect the rotational speed fluctuation of the rotating disk 201, that is, the rotational speed fluctuation of the transfer conveyance belt 60.
In this embodiment, the difference data written to the RAM 102 or the EEPROM 111 is the difference data with the immediately preceding value, but it is not necessary to limit to the immediately preceding value.

  As described above, in the second embodiment, data for one rotation of the rotating disk 201 obtained by the density sensor 202 when the transfer conveyance belt 60 that does not perform the image forming process is rotating at a constant speed is stored in the EEPROM 111 ( Alternatively, the data stored in advance in the RAM 102) is a data difference. Therefore, it is possible to reduce the amount of data stored in the EEPROM 111 in advance. In particular, if the density pattern formed on the outer peripheral surface of the rotary disk 201 is a pattern in which the reflectance gradually changes, the data capacity can be greatly reduced.

[Third embodiment]
Next, a third embodiment will be described with reference to FIGS.
FIG. 9 is an explanatory diagram showing a first development example of a part of the rotating disk 201 attached to the shaft of the lower right roller 66 and the density pattern on the outer peripheral surface thereof.
In FIG. 9, the density pattern formed in the circumferential direction on the outer peripheral surface of the rotating disk 201 has a reflectivity detected by the density sensor 202 from a high reflectance (white) to a low reflectance according to the rotation of the rotating disk 201. It is composed of a plurality of marks that gradually change to (black).

  In the third embodiment, a specific reflectivity serving as a reference is determined, and a mark having the reflectivity is set as a mark having the highest reflectivity (white). This is because the reflectivity detected by the density sensor 202 gradually changes from a high reflectivity (white) to a low reflectivity (black) in accordance with the rotation of the rotating disk 201. This is because when the rotating disk 201 rotates once, the reflectance to be switched is suddenly switched from the lowest reflectance (black) to the highest reflectance (white), and the detection error can be minimized. .

  Here, specific processing (control) according to the present invention by the CPU 101 in the case where the density pattern formed on the outer peripheral surface of the rotating disk 201 has been described with reference to FIG. I will explain. Note that the control reflects the control of the second embodiment, but the control of the first embodiment may be reflected.

FIG. 10 is a flowchart showing a first example of pre-processing by the CPU 101 according to the present invention.
FIG. 11 is a flowchart showing a first example of main control by the CPU 101 according to the present invention.
First, the CPU 101 executes preprocessing as shown in FIG.
That is, first, in step S 1, the drive motor 32 as a measurement target is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates.

Next, in step S2, the presence or absence of an interrupt from the reflectance detection unit 108 is checked.
Here, the reflected light from the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 as an analog potential while sequentially changing. The reflectance detection unit 108 converts the analog potential from the density sensor 202 into a digital value by the ADC 114 and outputs the digital value. When the digital value is equal to or greater than a predetermined threshold, that is, the reflection detected using the density sensor 202. When the rate is a specific reflectance (the highest reflectance), an interrupt is generated for the CPU 101.

When the CPU 101 receives an interrupt from the reflectance detection unit 108 (when the reflectance detected using the density sensor 202 is a specific reflectance), the detection by the density sensor 202 on the outer peripheral surface of the rotating disk 201 is performed. The position is recognized as a reference position, and the process proceeds to step S3, where a digital value (reflectance detected using the density sensor 202) corresponding to the output value of the density sensor 202 is obtained from the reflectance detection unit 108, and the digital value is obtained. Is written in the RAM 102 as an initial value, and the internal counter value is cleared to “0” in step S4.
Next, in step S5, the timer (periodic timer) 110 is started to start time measurement from “0”, the internal counter value is incremented (+1) in step S6, and the reflectance detection unit 108 in steps S7 and S8. Alternatively, an interrupt from the timer 110 is awaited.

  When an interrupt from the timer 110 is detected, a digital value (data) corresponding to the output value of the density sensor 202 is acquired in step S9, and a difference from the immediately preceding value (initial value is initially set) is calculated in step S10. The difference data is written in the RAM 102 together with the internal counter value at that time in step S11. The internal counter value corresponds to the number of activations of the timer 110, that is, the number of acquisitions of a digital value corresponding to the output value of the density sensor 202, and this is used as an identifier for subsequent data reading.

After performing the processing of step S11, in order to acquire data corresponding to the next output value of the density sensor 202, the timer 110 is restarted in step S5, and time measurement is started again from “0”. In step S6, the internal counter value is incremented (+1).
Thereafter, a digital value (data) corresponding to the output value of the density sensor 202 is acquired every interruption period of the timer 110, and the difference from the data corresponding to the output value of the density sensor 202 acquired by the previous internal counter value is obtained. Data is sequentially written into the RAM 102 (steps S5 to S11).

Thereafter, when an interrupt from the reflectance detection unit 108 is received (when the reflectance detected using the density sensor 202 is a specific reflectance), the detection by the density sensor 202 on the outer peripheral surface of the rotating disk 201 is performed. The position is recognized as the reference position, and the preprocessing of FIG.
In this way, data for one rotation of the rotating disk 201 can be stored in the RAM 102. Then, when the acquisition of the necessary data (accumulation in the RAM 102) is completed, the necessary data (data for one rotation of the rotating disk 201) in the RAM 102 is transferred to the EEPROM 111 to be written and stored.

On the other hand, the CPU 101 performs control (main control) related to detection of rotational speed fluctuations of the rotating disk 201 (lower right roller 66) as shown in FIG.
That is, during the image forming process, first, in step S21, the drive motor 32 that is the measurement target is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107. The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates.

Next, in step S22, the presence or absence of an interrupt from the reflectance detection unit 108 is checked, and when an interrupt from the reflectance detection unit 108 is received (the reflectance detected using the density sensor 202 is a specific reflectance). In this case, the position detected by the density sensor 202 on the outer peripheral surface of the rotating disk 201 is recognized as the reference position, and the process proceeds to step S23. The reflectance detected by using 202 is acquired, and the digital value is written in the RAM 102 as an initial value, and the internal counter value is cleared to “0” in step S24.
Next, in step S25, the timer (periodic timer) 110 is activated to start time measurement from “0”, the internal counter value is incremented (+1) in step S26, and the reflectance detection unit 108 in steps S27 and S28. Alternatively, an interrupt from the timer 110 is awaited.

When an interrupt from the timer 110 is detected, a digital value (data) corresponding to the output value of the density sensor 202 is acquired in step S29, and a difference from the immediately previous value (initial value) is calculated in step S30.
Next, in step S31, preprocess data (difference data) corresponding to the internal counter value (initially “1”) at that time is read from the EEPROM 111, and the difference data is compared with the previously calculated difference data in step S32. If the comparison result is less than the predetermined threshold value, it is determined that there is no fluctuation in the rotational speed of the rotary disk 201, that is, there is no fluctuation in the rotational speed of the transfer conveyance belt 60, and the process returns to step S25.

In step S25, the timer 110 is restarted to start time measurement again from “0”. In step S26, the internal counter value is incremented (+1), and in steps S27 and S28, the reflectance detection unit 108 or timer is restarted. 110 is waiting for an interrupt from 110.
Thereafter, a digital value (data) corresponding to the output value of the density sensor 202 is acquired every interruption period of the timer 110, and the difference from the data corresponding to the output value of the density sensor 202 acquired by the previous internal counter value is obtained. Data and the corresponding preprocess data are sequentially compared using the internal counter value as an identifier (steps S25 to S32).

If the comparison result is equal to or greater than a predetermined threshold value, it is determined that the rotation speed of the rotary disk 201, that is, the rotation speed of the transfer conveyance belt 60 has fluctuated, and the process proceeds to an error processing routine (not shown). Inform. For example, the determination result is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).
Further, if the rotating disk 201 makes one rotation with no change in the rotation speed of the transfer conveyance belt 60, an interruption from the reflectance detection unit 108 is accepted again (step S27). In this case, the position detected by the density sensor 202 on the outer peripheral surface of the rotating disk 201 is recognized as the reference position again, a digital value corresponding to the output value of the density sensor 202 is acquired, and is used as an initial value in step S23. The value is reset in the RAM 102, and the internal counter value is cleared to "0" in step S24.

  As described above, in the third embodiment, when the same control as in the second embodiment (or the first embodiment may be performed), out of the reflectance of the density pattern formed on the outer peripheral surface of the rotating disk 201. By detecting a specific reflectance by the density sensor 202, the data obtained by the density sensor 202 and the data held in the EEPROM 111 are compared in synchronization every predetermined time. This can be done accurately without adding parts. Therefore, the cost of the belt drive device 6 can be reduced.

[Fourth embodiment]
Next, a fourth embodiment will be described.
In the preprocessing of the third embodiment described with reference to FIG. 10, the acquisition of data for one rotation of the rotating disk 201 is started when a specific reflectance is detected by the density sensor 202, that is, the output value of the density sensor 202. This is performed by interruption from the reflectance detection unit 108 to the CPU 101 when the digital value corresponding to (analog potential) is greater than or equal to a predetermined threshold (highest reflectance = white) (step S2). In the main control of the third embodiment described with reference to FIG. 11 (control related to detection of rotational fluctuation of the rotating disk 201), acquisition of data for one rotation of the rotating disk 201 is started by detecting the same condition (step S22). Then, the data acquired in the preprocessing and the data acquired in the main control are compared (step S32).

  Also, the position of the mark with the highest reflectance (white) corresponding to the stationary angle of the lower right roller 66 (the rotational angle when the rotating disk 201 is stationary) before the start of preprocessing (the reflectance constituting the density pattern). In the pre-processing of the third embodiment, the drive motor 32 is driven (if any one of the different marks) is at a position downstream of the position opposite to the density sensor 202 with respect to the rotation direction of the rotary disk 201 ( From step S1) until the specific reflectance on the density pattern formed on the outer peripheral surface of the rotating disk 201 is detected by the density sensor 202 (step S2-Yes), the rotating disk 201 is rotated at most once. I have to let it.

On the other hand, in the fourth embodiment, data for one rotation of the rotating disk 201 obtained by the density sensor 202 when the rotating disk 201 is rotating at a constant speed during preprocessing is stored in the EEPROM 111 in advance. When setting, the detection start position is set to one rotation from the arbitrary position (reflectance) on the density pattern formed on the outer peripheral surface of the rotating disk 201 until the position (reflectance) is detected again. The data corresponding to the reflectance (digital value corresponding to the output value of the density sensor 202) is stored in the EEPROM 111, the data obtained by the density sensor 202 every predetermined time during the main control, and the data held in the EEPROM 111 Is synchronized with the reflection of the detection start position from the density pattern formed on the outer peripheral surface of the rotating disk 201. It is carried out by detecting by the density sensor 202.
According to the fourth embodiment, it becomes possible to immediately execute the pre-processing regardless of the position of the stationary angle of the rotating disk 201 before the start of the pre-processing, thereby increasing the processing efficiency.
The characteristic part of the fourth embodiment can be added to the first embodiment or the second embodiment.

[Fifth embodiment]
Next, a fifth embodiment will be described with reference to FIG.
FIG. 12 is a timing chart showing an example in which the interrupt period of the timer 110 differs with respect to the output value (analog potential) of the density sensor 202.

  When the density pattern formed on the outer peripheral surface of the rotating disk 201 is as shown in FIG. 9, the reflectance of the density pattern detected by the density sensor 202 is changed from high reflectance (white) to low reflectance (black). Since it gradually changes, as shown in FIG. 12, the output value (analog potential) of the density sensor 202 gradually changes from a high value to a low value. Therefore, if the reflectance detected first by the density sensor 202 is the highest reflectance, when the lower right roller 66 makes one rotation (one turn), the lowest reflectance (black) to the highest reflectance (white). ), The output value of the density sensor 202 is suddenly switched from a low value to a high value.

  The main control of the third embodiment described with reference to FIG. 11 (in the control relating to the detection of the rotational speed fluctuation of the rotating disk 201, the detection of a specific reflectance, that is, the reflectance detector 108 is the ADC 114 and the output value of the density sensor 202 (analog Potential) is converted to a digital value, and when it is equal to or higher than a predetermined threshold (highest reflectance = white), the CPU 101 changes the output value of the density sensor 202 every interruption period from the timer 110. The corresponding digital value is acquired, the difference data between the digital value corresponding to the output value of the density sensor 202 acquired with the previous internal counter value, and the corresponding preprocessing data (in the EEPROM 111) using the internal counter value as an identifier The process of sequentially comparing the difference data) is repeated (steps S25 to S32).

  When the rotating disk 201 rotates once, the reflectance of the density pattern detected by the density sensor 202 is switched from the lowest reflectance (black) to the highest reflectance (white). Data exceeding the threshold (highest reflectance = white) is detected, and an interrupt is generated in the CPU 101 (step S27—Yes).

  At this time, as shown in FIG. 12A, when one rotation period of the rotating disk 201 is not an integral multiple of the interrupt period (timer period) of the timer 110, reflection is performed while the timer 110 is activated. An interrupt is generated from the rate detection unit 108. The CPU 101 clears the internal counter value to “0” by the interrupt (step S24), and restarts the timer 110 (step S25). As a result, the interrupt cycle of the timer 110 that is constant, that is, the acquisition timing of the digital value corresponding to the output value of the density sensor 202 is shifted at the timing when the rotating disk 201 makes one rotation, and a cycle fluctuation occurs.

On the other hand, in the fifth embodiment, the period of one rotation of the rotating disk 201 is an integral multiple of the period of the timer 110 (the period for acquiring the digital value corresponding to the output value of the density sensor 202).
According to the fifth embodiment, when the rotating disk 201 rotates once and the reflectance detection unit 108 detects data that is equal to or higher than a predetermined threshold value (highest reflectance = white) again, the CPU 101 is interrupted. When generated (step S27-Yes), as shown in FIG. 12B, since one rotation period of the rotating disk 201 is an integral multiple of the period of the timer 110, an interruption from the reflectance detection unit 108 is performed. Interrupts from the timer 110 occur almost simultaneously. Strictly speaking, since the interrupt of the reflectance detection unit 108 occurs first in the order of the processing shown in the flowcharts of FIGS. 10 and 11, the CPU 101 clears the internal counter value to “0” (step S24), The timer 110 is restarted (step S25).

As a result, the interrupt cycle of the timer 110 can be made constant without causing cycle fluctuations even at the timing when the rotating disk 201 makes one rotation, and therefore the timing for acquiring the digital value corresponding to the output value of the density sensor 202 is also constant. Can be.
In addition, the characteristic part of 5th Example can also be added to 1st Example, 2nd Example, or 4th Example.

[Sixth embodiment]
Next, a sixth embodiment will be described with reference to FIGS.
FIG. 13 is a diagram showing an example of the relationship between the internal counter value and the output value of the density sensor 202 during pre-processing and main control by the CPU 101.
When the density pattern formed on the outer peripheral surface of the rotating disk 201 is as shown in FIG. 9, the reflectance of the density pattern detected by the density sensor 202 is changed from high reflectance (white) to low reflectance (black). Since it gradually changes, as shown in FIG. 13, the output value of the density sensor 202 also gradually changes from a high value to a low value.

In the pre-processing (for example, the one described with reference to FIG. 10), the CPU 101 outputs the output value (actually the corresponding digital value) P _n at the internal counter value = n and the previous internal counter value = n. The difference ΔP _n with respect to the output value P _n−1 of the density sensor 202 at −1 is calculated and written in the RAM 102 as difference data at the internal counter value = n. In the main control (control relating to detection of fluctuations in the rotational speed of the rotating disk 201), the output value P _{n ′} of the density sensor 202 at the internal counter value = n ′ and the density sensor at the previous internal counter value = n′−1. When the difference ΔP _{n ′} with the output value P _{n′−1 of} 202 is calculated, the difference data ΔP _n in the internal counter value n (= n ′) is read from the RAM 102, and ΔP _{n ′} and ΔP _n are compared.

FIG. 13A shows a state in which noise is mixed in the output value P _{n ′} of the density sensor 202 when the internal counter value = n ′ in the main control.
In the belt driving device 6 of this laser printer, unexpected noise may be mixed into the control signal during the image forming process due to the influence of the transfer bias power supply 9 (9Y, 9M, 9C, 9K) or the like.

In FIG. 13A, the output value P _{n ′} of the density sensor 202 is data including noise in the positive direction, and difference data ΔP _{n ′ from} the immediately preceding value of the density sensor 202 when the internal counter value = n ′. Is smaller than the original difference data. When acquiring the difference data ΔP _n from the immediately preceding value of the density sensor 202 at the internal counter value = n in the preprocessing, since the transfer bias power source 9 and the like are not turned on, the original difference data is acquired. Yes. Therefore, when ΔP _{n ′} and ΔP _n are compared, there is a difference corresponding to noise.
Therefore, in the sixth embodiment, when the reflectance data of the density pattern formed on the outer peripheral surface of the rotating disk 201 obtained by the density sensor 202 is acquired every predetermined time, the reflectance data is obtained from the predetermined time. Sampling and averaging sequentially within a short time.

Here, specific control of the sixth embodiment will be described with reference to FIG. 13B and FIGS.
FIG. 14 is a block diagram showing another hardware configuration example of the control unit including the drive motor control unit of the belt driving device 6 in this laser printer. Parts corresponding to those in FIG. Description is omitted.

In the sixth embodiment, the laser printer is provided with a control unit 100 shown in FIG. In the control unit 100, a timer (sampling timer) 116 is provided separately from the timer (period timer) 110.
The timer 116 is a sampling timer, which is activated by an instruction (repeatedly performed) from the CPU 101 (starts time measurement from “0”), and is sent to the CPU 101 at a predetermined timing (when a preset predetermined time is reached). An interrupt is generated. Note that the predetermined time set in the timer 116 is shorter than the predetermined time set in the timer 110.

FIG. 15 is a flowchart showing a second example of preprocessing according to the present invention by the CPU 101 of FIG.
FIG. 16 is a flowchart showing a second example of the main control according to the present invention by the CPU 101 of FIG.
FIG. 17 is a flowchart illustrating an example of a subroutine of average data acquisition processing in FIGS. 15 and 16.
The first internal counter value (Count1) in FIG. 15 corresponds to the internal counter value (Count) in FIG.

  In the flowchart of FIG. 15, the data acquisition process of step S <b> 9 in the preprocessing is changed to an average data acquisition process compared to the flowchart of FIG. 10. In the flowchart of FIG. 16, the data acquisition process in step S <b> 29 in the main control (control related to detection of fluctuations in the lower right roller 66) is changed to the average data acquisition process as compared with the flowchart of FIG.

  In the average data acquisition process subroutine of FIG. 17, when an interrupt is generated from the timer 110 (step S8-Yes or step S28-Yes), the CPU 101 of FIG. 14 sets the digital value corresponding to the output value of the density sensor 202 to the first. Is sampled (acquired) as data (step S41). Then, a prescribed value is set in the second internal counter value (Count2) (step S42), the timer (sampling timer) 116 is started and time measurement is started from “0” (step S43). An interrupt wait state is entered (step S44-No).

Here, the product of the second internal counter value (specified value) and the set period of the timer 116 corresponds to the width for performing the averaging process on the density pattern formed on the outer peripheral surface of the rotating disk 201. It will be.
When the CPU 101 detects an interrupt from the timer 116 (step S44—Yes), the digital value corresponding to the output value of the density sensor 202 is sampled as second data (step S45).

Next, the second internal counter value is decremented (−1) (step S46), and if the second internal counter value is not “0” (step S47—No), the timer 116 is started again and “ Time measurement is started again from "0" (step S43), and the state again waits for an interrupt from the timer 116 (step S44-No).
In this manner, digital values (data) corresponding to the output value of the density sensor 202 for the specified value (specified number of times) set as the second internal counter value are sequentially sampled, and the second internal counter value is “0”. (Step S47-Yes), the average value of the sampled digital values for the specified number of times is calculated (Step S48).

FIG. 13B shows the case where noise is mixed in the output value P _{n ′} of the density sensor 202 when the internal counter value = n ′ in the main control (control related to detection of fluctuations in the rotational speed of the rotating disk 201). The mode which performed control of the flowchart of FIGS. 15-17 is shown.
In FIG. 13B, the Δt period from the time when the output value P _{n ′} (actually the digital value corresponding thereto) of the density sensor 202 at the internal counter value = n ′ is sampled with respect to FIG. The output value of the density sensor 202 is averaged until elapses.
At the time when the internal counter value = n ′, the output value P _{n ′} is data including noise in the positive direction, but the average of the data in the Δt period including data including noise in the negative direction that is generated thereafter. By acquiring, the noise component can be canceled.

As described above, the difference data ΔP _{n ′} in the main control is the average value of the output value P _{n ′} of the density sensor 202 when the internal counter value = n ′ and the density sensor when the previous internal counter value = n′−1. It calculates _{| requires} by calculating the difference with the average value of 202 output value _Pn'-1 . Similarly, the difference data ΔP _{n in the} preprocessing is the average value of the output value P _n of the density sensor 202 when the internal counter value = n, and the output value P of the density sensor 202 when the previous internal counter value = n−1. Obtained by calculating the difference from the average value of _n-1 .
Therefore, since ΔP _{n ′} is compared with ΔP _n and the comparison result is _equal to or greater than a predetermined threshold (step S32—Yes), the rotation speed of the rotary disk 201, that is, the rotation speed of the transfer conveyance belt 60 fluctuates. It is possible to reduce the contribution of a sudden noise component in the case of judging that.

[Seventh embodiment]
Next, a seventh embodiment will be described with reference to FIG.
FIG. 18 is an explanatory diagram showing a second development example of a part of the rotating disk 201 attached to the shaft of the lower right roller 66 and the density pattern on the outer peripheral surface thereof.
In FIG. 18A, the density pattern formed on the outer peripheral surface of the rotating disk 201 is composed of a plurality of marks having different reflectances depending on the position of the rotating disk 201 in the circumferential direction.

Printing (forming) a pattern on the outer peripheral surface (curved surface) of the rotating disk 201 is not easy in terms of processing.
Therefore, in the seventh embodiment, in the belt driving device 6 having the same configuration as that of any of the first to sixth embodiments, the density pattern is the lower right roller 66 (the driving roller 63, the inlet roller 61, or the outlet roller 62). It is printed on a sticker that is attached along the circumferential direction to the outer peripheral surface of the rotating disk 201 attached to a good shaft.
According to the seventh embodiment, since a rectangular seal on which a density pattern is printed may be attached to the outer peripheral surface of the rotating disk 201, the density pattern can be formed on the rotating disk 201 by a simple method, and the cost can be reduced. Leads to.

[Eighth embodiment]
Next, an eighth embodiment will be described with reference to FIG.
In FIG. 18B, the density pattern formed on the outer peripheral surface of the rotating disk 201 is a pattern that gradually changes from a low reflectance (black) to a high reflectance (white) in the circumferential direction of the rotating disk 201. Alternatively, the pattern gradually changes from a high reflectance (white) to a low reflectance (black) in the circumferential direction of the rotating disk 201.

  In the eighth embodiment, the belt drive device 6 having the same configuration as that of any of the first to sixth embodiments is attached to the shaft of the lower right roller 66 (which may be the drive roller 63, the entrance roller 61, or the exit roller 62). Rotating a seal printed with a density pattern composed of a plurality of marks whose reflectivity gradually changes from low reflectivity to high reflectivity or from high reflectivity to low reflectivity in the circumferential direction of the rotating disk 201 The structure is affixed to the disk 201.

  According to the eighth embodiment, both ends of the seal formed by any of the patterns shown in FIG. 18B have the lowest reflectance (black) and the highest reflectance (white). For example, if the third embodiment reflects the characteristic part of the eighth embodiment (use of the above-mentioned seal), a mark with a specific reflectivity serving as a reference may be a high reflectivity (white) mark or a low reflectivity ( When the rotating disk 201 is rotated once by setting a black mark, the lowest reflectance (black) to the highest reflectance (white), or the highest reflectance (white) to the lowest reflectance (black). Therefore, there is an advantage that the detection error can be minimized.

  In addition, if a marginal part extending the mark with the same reflectance is provided at one end (one of both ends) of the seal so as to overlap and bond, the processing performance can be improved. Also in this case, since the reflectance is a portion that changes sharply, the influence of the thickness due to the overlapping on the sensitivity of the density sensor 202 can be reduced.

[Ninth embodiment]
Next, a ninth embodiment will be described with reference to FIG.
FIG. 19 is a perspective view illustrating the configuration of the transfer conveyance belt 60 in the belt driving device 6 when the target roller is the driving roller 63.
As described above, the drive roller 63 is connected to the drive motor 32 via the timing belt 33, and is driven to rotate in proportion to the rotation speed of the drive motor 32. When the driving roller 63 rotates, the transfer / conveying belt 60 is driven, and when the transfer / conveying belt 60 is driven, the lower right roller 66 rotates. Then, the transfer conveying belt 60 is frictionally driven by the rotation of the driving roller 63, and the lower right roller 66 is frictionally rotated by driving the transfer conveying belt 60.

In the ninth embodiment, the inertia moment is increased by connecting the flywheel 203 to the rotation shaft of the drive roller 63 in order to stabilize the rotation speed of the transfer conveyance belt 60.
The density pattern for detecting the rotational speed fluctuation of the transfer conveyance belt 60 is affixed to the outer peripheral surface (side surface) of the flywheel 203 with a seal formed by the density pattern used in the seventh embodiment or the eighth embodiment. In addition, the density pattern on the outer peripheral surface is detected by the density sensor 202.

The density pattern on the outer peripheral surface of the flywheel 203 connected to the rotating shaft of the driving roller 63 is not a configuration in which the rotating disk 201 is attached to the lower right roller 66 and the density sensor 202 detects the density of the density pattern on the outer peripheral surface. Is the same as that of any one of the first to eighth embodiments except that the density sensor 202 is used.
According to the ninth embodiment, the flywheel 203 necessary for the function of the drive control device also serves as the function of the rotating disk 201 that is indispensable in each of the embodiments described above, whereby the rotating disk 201 can be reduced. This contributes not only to cost advantages but also to securing an effective space on the device layout.

[Tenth embodiment]
Next, a tenth embodiment will be described with reference to FIG.
FIG. 20 is a front view for explaining an example in which the main configuration of the belt driving device 6 is different when the target roller is the lower right roller 66.

As described with reference to FIGS. 2 and 3, the drive roller 63 is connected to the drive motor 32 via the timing belt 33 and is driven to rotate in proportion to the drive speed of the drive motor 32. Then, the transfer conveyance belt 60 is rotated by the rotation of the driving roller 63, and the lower right roller 66 is rotated by the rotation.
In addition, a cleaning device 85 including a brush roller and a cleaning blade is disposed on the outer peripheral surface of a portion of the transfer conveyance belt 60 that is wound around the driving roller 63. The toner adhering to 60 is removed.

However, in the case of the cleaning mechanism of the cleaning blade type, toner accumulates at the blade edge portion, and the toner may fall or scatter. The falling toner stains the inside of the apparatus or reattaches to the transfer / conveying belt 60, but of course, the toner may fall on the outer peripheral surface of the rotating disk 201 attached to the shaft of the lower right roller 66. There is.
Therefore, when the density sensor 202 is disposed below the rotating disk 201 as shown in FIG. 20A, the toner that has fallen on the outer peripheral surface of the rotating disk 201 moves along with the rotation of the rotating disk 201. When attached to the light irradiating unit 202 or the light detecting unit (light receiving unit) 202, the reflectance of the density pattern on the outer peripheral surface of the rotating disk 201 is lower than the original reflectance due to the deterioration of the irradiation light amount and the shortage of the received light amount. The reflectance may be detected, or the reflectance itself cannot be detected.

Therefore, in the tenth embodiment, the density sensor 202 is disposed on the upper side (above) of the rotating disk 201 as shown in FIG. Others are the same as any one of the first to eighth embodiments.
When the density sensor 202 detects the density pattern on the outer peripheral surface of the flywheel 203 connected to the rotation shaft of the drive roller 63 as in the ninth embodiment described with reference to FIG. It is preferable to arrange the density sensor 202 on the upper side.
According to the tenth embodiment, the density sensor 202 is connected to the rotating disk 201 even when foreign matter such as toner dropped or scattered from the outer peripheral surface of the transfer conveyance belt 60 falls on the outer peripheral surface of the rotating disk 201 (or flywheel 203). Since the light irradiation part and the light detection part are arranged downward, the possibility that the toner on the outer peripheral surface of the rotating disk 201 will adhere to the light irradiation part or the light detection part of the density sensor 202 is reduced. .

[Eleventh embodiment]
Next, an eleventh embodiment will be described with reference to FIG.
FIG. 21 is a perspective view illustrating a second example of the main configuration of the belt driving device 6 when the target roller is the lower right roller 66.

As described above, in the case of the cleaning mechanism of the cleaning blade type, toner accumulates at the blade edge portion, and the toner may fall or scatter. The falling toner stains the inside of the apparatus or reattaches to the transfer / conveying belt 60, but of course, the toner may fall on the outer peripheral surface of the rotating disk 201 attached to the shaft of the lower right roller 66. There is.
For this reason, if falling toner adheres to the outer peripheral surface of the density pattern formed on the outer peripheral surface of the rotating disk 201, the reflectance of the density pattern becomes a value different from the original reflectance, which is If detected by the sensor 202, normal control cannot be performed.

  Therefore, in the eleventh embodiment, as shown in FIG. 21, in addition to the variation detection mechanism of the transfer conveyance belt 60 in the tenth embodiment shown in FIG. 20B, in order to clean the surface of the density pattern, A brush-shaped or blade-shaped cleaning member 204 is attached to the density sensor 202 with respect to the rotation direction of the rotary disk 201 attached to the shaft of the lower right roller 66 (which may be the drive roller 63, the entrance roller 61, or the exit roller 62). It is provided upstream of the position where the irradiated light is reflected. However, the attachment position of the cleaning member 204 is not necessarily upstream. Except for providing the cleaning member 204, it is the same as any one of the first to eighth and tenth embodiments.

When the density sensor 202 detects the density pattern on the outer peripheral surface of the flywheel 203 connected to the rotation shaft of the drive roller 63 as in the ninth embodiment described with reference to FIG. It is preferable to provide a cleaning member (same as the cleaning member 204) for cleaning the surface of the surface upstream of the position where the light irradiated by the density sensor 202 reflects with respect to the rotation direction of the flywheel 203.
According to the eleventh embodiment, even when the toner dropped or scattered from the surface of the transfer conveyance belt 60 adheres to the density pattern formed on the outer peripheral surface of the rotating disk 201 (or flywheel 203), By cleaning the surface of the density pattern with the cleaning member 204, a reflectance different from the original reflectance of the density pattern is not detected by the density sensor 202, so that a good detection is possible.

[Twelfth embodiment]
Next, a twelfth embodiment will be described.
In the seventh embodiment, the eighth embodiment, or the ninth embodiment described above, a structure in which a seal printed with a density pattern is attached to the outer peripheral surface of the rotary disk 201 or flywheel 203 attached to the shaft of the lower right roller 66 It is said. In this configuration, in the unlikely event that the seal is peeled off, the reflectance of the rotating disk 201 or flywheel 203 on which nothing is affixed is read by the density sensor 202. Since the rotating disk 201 or the flywheel 203 is formed of a uniform material, the reflectance thereof is always a constant value.

On the other hand, in the twelfth embodiment, when a plurality of data (reflectance data) obtained by the density sensor 202 does not change with the rotation of the rotary disk 201 or the flywheel 203, the CPU 101 (FIG. 8 or FIG. FIG. 14) determines that the device is in an abnormal state, and notifies the device diagnosis abnormality (“the state where the seal attached to the outer peripheral surface of the rotating disk or flywheel has been peeled off”). For example, the device diagnosis abnormality is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown). Except for the processing, it is the same as the seventh embodiment or the eighth embodiment.
According to the twelfth embodiment, it is possible to notify the user of the abnormality by detecting and notifying the abnormal state of the device.

[Thirteenth embodiment]
Next, a thirteenth embodiment will be described with reference to FIG.
FIG. 22 is a block diagram showing still another hardware configuration example of the control unit including the drive motor control unit of the belt driving device 6 in this laser printer, and parts corresponding to those in FIG. Most of those explanations are omitted.

In the thirteenth embodiment, the laser printer is provided with a control unit 100 shown in FIG. The control unit 100 adds an integration circuit 117 and a constant current circuit 118 that constitute a control circuit that varies the amount of light emitted from the density sensor 202 to the control unit 100 shown in FIG.
The CPU 101 shown in FIG. 22 has a built-in PWM generation module that generates a PWM (Pulse Width Modulation) signal.
The integrating circuit 117 generates an integrated waveform (DC level) according to the PWM duty of the PWM signal from the CPU 101.

  The constant current circuit 118 is composed of an operational amplifier and an NPN transistor. The non-inverting input terminal of the operational amplifier is the output terminal of the integrating circuit 117, the inverting input terminal is the emitter terminal of the NPN transistor, and the output terminal is the NPN type. Each is connected to the base terminal of the transistor. The emitter terminal of the NPN transistor is grounded via a resistor, and the collector terminal is connected to the cathode terminal of the light irradiation part (herein referred to as “light emitting diode”) of the concentration sensor 202.

  The constant current circuit 118 can draw the collector current corresponding to the DC level of the integrating circuit 117, that is, the forward current of the light emitting diode (LED) of the concentration sensor 202. Since the operational amplifier of the constant current circuit 118 operates so that the potentials of the non-inverting input terminal and the inverting input terminal are equal, the CPU 101 can control the irradiation light amount (light emission amount) of the light emitting diode of the density sensor 202 by the PWM duty. it can.

  The light emitting diode of the concentration sensor 202 has temperature dependency, and the luminance decreases as the temperature increases, and the luminance increases as the temperature decreases. Similarly, the light detection portion (herein referred to as “phototransistor”) of the density sensor 202 also has temperature dependency, and the DC current gain increases as the temperature rises. In addition, the density pattern formed on the outer peripheral surface of the rotating disk 201 may have an overall density offset variation depending on the manufacturing lot. Furthermore, since the light emitting diode of the density sensor 202 deteriorates with time, the luminance decreases with the years.

  Therefore, in the thirteenth embodiment, when the plurality of data obtained by the density sensor 202 is data that uniformly shows a reflectance lower than the normal range as the rotary disk 201 rotates, the CPU 101 The on-duty is increased and the DC level of the integration value of the integration circuit 117 is increased. As a result, the potential of the non-inverting input terminal of the operational amplifier in the constant current circuit 118 rises, so that the collector current is increased so as to raise the potential of the inverting input terminal, that is, the emitter terminal of the NPN transistor. Accordingly, the amount of light emitted from the density sensor 202 also increases.

  In addition, when the plurality of data obtained by the density sensor 202 is data that shows a reflectance that is uniformly higher than the normal range as the rotating disk 201 rotates, the CPU 101 reduces the on-duty of the PWM. Then, the DC level of the integration value of the integration circuit 117 is lowered. As a result, since the potential of the non-inverting input terminal of the operational amplifier in the constant current circuit 118 is lowered, the collector current is decreased so as to lower the potential of the inverting input terminal, that is, the emitter terminal of the NPN transistor. Accordingly, the amount of light emitted from the density sensor 202 is also reduced.

  Furthermore, when the plurality of data obtained by the density sensor 202 is data that shows a higher reflectance or lower reflectance than the normal range as the rotating disk 201 rotates, the irradiation light amount of the density sensor 202 is changed. If the obtained data does not fall within the normal range even after the increase / decrease, it is determined that the device is in an abnormal state and a device diagnosis abnormality is notified. For example, the device diagnosis abnormality is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).

Here, specific control of the thirteenth embodiment will be described with reference to FIGS.
FIG. 23 is a flowchart showing a third example of preprocessing according to the present invention by the CPU 101 of FIG.
FIG. 24 is a flowchart illustrating an example of a subroutine of the reflectance offset detection process in FIG.
Note that the first internal counter value (Count1) in FIG. 23 corresponds to the internal counter value (Count) in FIG. The average data acquisition processing subroutine in FIG. 23 is the same as that shown in FIG. The main control is the same as that shown in FIG.

  In the flowchart of FIG. 23, the reflectance offset detection process (a plurality of data obtained by the density sensor 202 has a reflectance that is uniformly higher or lower than the normal range in the main routine of the pre-processing compared to the flowchart of FIG. And a determination as to whether or not the irradiation light quantity of the density sensor 202 has been changed as a result of the reflectance offset detection process and a determination as to whether or not the device is in an abnormal state is added (steps S52 to S57). Further, initialization of the device abnormal condition determination counter (step S51) and a subroutine for reflectance offset detection processing (FIG. 24) are added.

  An internal counter is used to determine the state of the device (laser printer), and the third internal counter value (Count3) determines that the data obtained by the density sensor 202 is lower than a predetermined value (the lower limit value of the normal range). The number of times, the fourth internal counter value (Count4) is the number of times that the data obtained by the density sensor 202 is determined to be higher than a predetermined value (the upper limit value of the normal range), and the fifth internal counter value (Count5) is the density sensor The number of times of increasing the irradiation light quantity of 202, and the sixth internal counter value (Count6) are used for counting the number of times of decreasing the irradiation light quantity of the density sensor 202.

In the subroutine of the reflectance offset detection process in FIG. 24, CPU 101 of FIG. 22, the output value (digital value corresponding thereto in practice) of the density sensor 202 in the internal counter value = n and the average value of P _n, 1 previous difference data [Delta] P _n obtained by calculating the difference between the average value of the output value P _n-1 of the density sensor 202 in the internal counter value = n-1 it is determined whether the lower than a predetermined value ( Step S61). If the difference data ΔP _n is not lower than the predetermined value and is within the normal range (step S61—No), it is determined whether or not the third internal counter value is “0” (step S63).

For the third internal counter value and the fourth internal counter value described later, prescribed values are written by initialization of the internal counter value group of the main routine (step S4).
If the third internal counter value is not “0” (step S63—No), it is determined whether or not the difference data ΔP _n is higher than a predetermined value (step S66). If the difference data ΔP _n is not higher than the predetermined value and is within the normal range (step S66—No), it is determined whether or not the fourth internal counter value is “0” (step S68). If the fourth internal counter value is not “0” (step S68—No), the subroutine of the reflectance offset detection process is exited.

When the difference data ΔP _n is lower than the predetermined value (step S61—Yes), the third internal counter value is decremented (−1) and the fourth internal counter value is set to a specified value (cleared). If the third internal counter value is not “0” (step S63—No), the process proceeds to determination of whether the difference data ΔP _n is higher than a predetermined value (step S66).

The case where the difference data ΔP _n is lower than the predetermined value continuously occurs (step S61—Yes), the third internal counter value is decremented (−1), and the fourth internal counter value is set to the specified value. As a result of the setting (step S62), if the value of the third internal counter value is “0” (step S63—Yes), the on-duty of the PWM is increased to increase the irradiation light amount of the density sensor 202. (Step S64), and after decrementing the fifth internal counter value (-1) (step S65), an adjustment flag indicating whether or not the irradiation light quantity of the density sensor 202 has been changed is set (step S71). Exit from the reflectance offset detection subroutine.

When the difference data ΔP _n is higher than the predetermined value (step S66—Yes), the fourth internal counter value is decremented (−1), and the third internal counter value is set to the specified value (cleared). If the fourth internal counter value is not “0” (step S68—No), the process exits the reflectance offset detection processing subroutine.

The case where the difference data ΔP _n is higher than the predetermined value continuously occurs (step S66—Yes), the fourth internal counter value is decremented (−1), and the third internal counter value is set to the specified value. As a result of the setting (step S67), if the fourth internal counter value is “0” (step S68—Yes), the on-duty of the PWM is decreased to reduce the irradiation light amount of the density sensor 202 ( Step S69) After decrementing the sixth internal counter value (-1) (Step S70), an adjustment flag indicating whether or not the irradiation light quantity of the density sensor 202 has been changed is set (Step S71), and the reflectance is set. Exit the offset detection subroutine.

In the main routine of the preprocessing of FIG. 23, when the first internal counter value is “1” (step S52—Yes), the output value P _n of the density sensor 202 at the first internal counter value = n the average value, when obtaining the difference data [Delta] P _n by calculating the difference between the average value of the output value P _n-1 of the density sensor 202 in the internal counter value = n-1 of the previous, the internal counter value = Since there is no average value of the output values P n−1 of the density sensor 202 at _n−1 , the reflectance offset detection process is not executed under this condition.

  In this case, in order to acquire data corresponding to the next output value of the density sensor 202, the timer 110 is restarted and time measurement is started again from “0” (step S5), and the first internal counter value is set. Increment (+1) (step S6), and then perform the determination and processing of steps S7 to S11 and proceed to step S52, but the first internal counter value is set to “2” by these processing (step S52). -No), it transfers to step S53 and performs the reflectance offset detection process mentioned above.

  Thereafter, the result of the reflectance offset detection process is determined by referring to the adjustment flag. That is, when the irradiation light quantity of the density sensor 202 is not changed in the subroutine of the reflectance offset detection process, the adjustment flag is not set (step S54-No), and therefore corresponds to the next output value of the density sensor 202. In order to obtain the digital value, the process returns to step S5, the timer 110 is restarted, the time measurement is started again from “0”, the internal counter value is incremented (+1) (step S6), and the reflectance detection is performed again. Waiting for an interrupt from the unit 108 or the timer 110 (step S7-No, step S8-No).

When an interrupt from the reflectance detection unit 108 is received again (step S7—Yes), it means that the rotating disk 201 has made one rotation, and thus the preprocessing is normally terminated.
In this way, a digital value (data) for one rotation of the rotating disk 201 can be stored in the RAM 102. When the acquisition of necessary data (digital value for one rotation of the rotating disk 201) is completed, the data is transferred to the EEPROM 111 to be written and stored.

  When the irradiation light quantity of the density sensor 202 is changed in the subroutine of reflectance offset detection processing, the adjustment flag is set (step S54-Yes), so the fifth internal counter value or the sixth internal counter value is set. Is determined to be “0” (steps S55 and S56). If none of the internal counter values is “0” (step S55-No, step S56-No), the adjustment flag is reset (step S57), and the irradiation light quantity of the density sensor 202 is changed. The preprocessing starting from the reflectance detection (step S2) is performed again.

  When either the fifth internal counter value or the sixth internal counter value is “0” (step S55—Yes or step S56—Yes), the irradiation light amount of the density sensor 202 is increased or decreased a predetermined number of times. However, it is determined that the obtained data does not fall within the normal range, that is, “the abnormal state of the light emitting diode that is the light emitting portion of the density sensor 202 or the phototransistor that is the light detecting portion”. Then, the abnormal state (device diagnosis abnormality) is notified by an error processing routine (not shown). For example, the abnormal state is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).

According to the thirteenth embodiment, the temperature dependency of the light irradiation part (light emitting diode) of the density sensor 202, the temperature dependency of the light detection part (phototransistor) of the density sensor 202, and the outer peripheral surface of the rotating disk 201 are formed. Optimum control is possible for variations in the density pattern depending on the production lot.
In addition, it is possible to optimally control the reduction in luminance due to the deterioration of the light irradiation part of the density sensor 202 over time.
Further, when there is an abnormality in the light irradiation unit or the light detection unit of the density sensor 202, the belt drive device 6 is in an abnormal state by detecting an increase or decrease in the reflected light amount when the irradiation light amount of the density sensor 202 is increased or decreased. It can be judged.

[14th embodiment]
Next, a fourteenth embodiment will be described with reference to FIG.
25 shows the density pattern formed on the outer peripheral surface of the rotating disk 201 attached to the shaft of the lower right roller 66 in the belt driving device 6 when the lower right roller 66 in FIG. 3 is the target roller. 6 is a timing chart showing an example of the relationship between the output value (analog potential) of the density sensor 202 and time when it is shown.

  The reflectance of the density pattern detected by the density sensor 202 gradually changes from high reflectance (white) to low reflectance (black). Therefore, in an ideal state where the rotating disk 201 is not decentered, the reflectance shown in FIG. As shown, the output value of the density sensor 202 gradually changes from a high value to a low value. Further, if the light intensity of the density sensor 202 is high and the distance between the density sensor 202 and the reflection position on the density pattern formed on the outer peripheral surface of the rotating disk 201 is short, the eccentricity of the rotating disk 201 has occurred. In addition, the linearity of the output transition of the density sensor 202 shown in FIG.

  However, when the amount of light emitted from the density sensor 202 is increased, an offset is generated in which the output value of the density sensor 202 does not change even if the reflectance of the density pattern changes, and the actual use area is narrowed. When the irradiation light quantity of the density sensor 202 is reduced, the linearity of the output transition of the density sensor 202 is impaired when the rotating disk 201 is eccentric as shown in FIG.

Therefore, in the fourteenth embodiment, the density sensor 202 has a configuration that can vary the amount of irradiation light (here, the control unit 100 shown in FIG. 22 is used), and the lower right roller 66 (the driving roller 63, the entrance roller 61, Alternatively, the density pattern formed on the rotating disk 201 attached to the rotating roller 201 attached to the outlet roller 62, that is, the density pattern for detecting the rotating angle of the rotating disk 201 has a reflectivity that varies depending on the rotating angle of the rotating disk 201. In the pattern, areas having uniform reflectance (uniform reflectance areas) appear at regular intervals.
The CPU 101 detects the uniform reflectance region of the density pattern by the density sensor 202 and adjusts (varies) the amount of light emitted from the density sensor 202 according to the reflectance.

FIG. 26 is an explanatory diagram showing a third development example of a part of the rotating disk 201 attached to the shaft of the lower right roller 66 and the density pattern on the outer peripheral surface thereof.
In FIG. 26, the density pattern formed on the outer peripheral surface of the rotating disk 201 is superimposed on a pattern that gradually changes from a high reflectance (white) to a low reflectance (black) as the rotating disk 201 rotates. A band portion (uniform reflectance region) having uniform reflectance is formed at regular intervals.

When the density pattern shown in FIG. 26 is detected by the density sensor 202, the output value (analog potential) has a waveform as shown in FIG.
FIG. 27 is a timing chart showing an example of the relationship between the output value of the density sensor 202 of FIG. 26 and time.
When the CPU 101 detects the uniform reflectance area in the pre-processing and the main control, the CPU 101 controls the on-duty of the PWM to adjust the irradiation light amount of the density sensor 202 so that the reflectance of the area becomes a predetermined value. .

  According to the fourteenth embodiment, when the irradiation light amount of the density sensor 202 is increased, an offset is generated in which the output value of the density sensor 202 does not change even if the reflectance of the density pattern changes, and the irradiation light amount of the density sensor 202 is reduced. In this case, when the eccentricity of the rotating disk 201 occurs, the irradiation light quantity of the density sensor 202 is optimal for the eccentricity of the rotating disk 201 with respect to the problem that the linearity of the output transition of the density sensor 202 is impaired. As a result, even when the eccentricity of the rotating disk 201 occurs, it is possible to perform good control without losing the linearity of the output (analog potential) transition of the density sensor 202.

[Fifteenth embodiment]
Next, a fifteenth embodiment will be described with reference to FIGS.
FIG. 28 is a flowchart showing first preprocessing (fourth example of preprocessing) according to the present invention by the CPU 101 of FIG.
FIG. 29 is a flowchart showing second preprocessing (fifth example of preprocessing) according to the present invention by the CPU 101 of FIG.
FIG. 30 is a flowchart showing an example of a subroutine of average data acquisition processing in FIG.

  Note that the first internal counter value (Count1) in FIG. 28 corresponds to the internal counter value (Count) in FIG. Also, the subroutine of the reflectance offset detection process in FIG. 29 is the same as that shown in FIG. Further, the main control is the same as that shown in FIG. However, the subroutine of the average data acquisition process of the main control is the same as that shown in FIG.

First, the first preprocessing of FIG. 28 will be described.
The CPU 101 first initializes the internal counter value (step S81). That is, the first internal counter value (Count1) is cleared to “0”, and the seventh internal counter value (Count7) is set to a specified value.

  Here, the first internal counter value corresponds to the number of activations of the timer 110, that is, the number of acquisitions of the output value (actually the corresponding digital value) of the density sensor 202, and serves as an identifier for writing and reading data in the RAM 102. The initial value is “0”. The seventh internal counter value corresponds to the number of adjustments of the irradiation light amount of the density sensor 202, that is, the total processing time relating to the adjustment of the irradiation light amount, and the initial value (specified value) is the uniform reflection area width and the rotation speed of the rotating disk 201. It is set so as to be within the allowable time for adjusting the irradiation light quantity determined in step (1).

Next, the CPU 101 drives the drive motor 32 to be measured via the I / O control unit 104, the drive motor I / F 106, and the driver 107 (step S82). The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates.
Next, it is checked whether or not there is an interruption from the reflectance detection unit 108 (step S83).

  Here, the reflected light in the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 as an analog potential while sequentially changing. The reflectance detection unit 108 converts the analog potential from the density sensor 202 into a digital value by the ADC 114 and outputs the digital value. When the digital value is equal to or greater than a predetermined threshold (highest reflectance = white), the CPU 101 Is interrupted (step S83-Yes).

When the CPU 101 receives an interrupt from the reflectance detection unit 108, the CPU 101 subsequently uses the density sensor 202 (actually also uses the reflectance detection unit 108) until the first uniform reflection region is detected from the reference position. The system waits for an interrupt from the detection unit 108 (step S84—No).
Thereafter, when an interruption from the reflectance detection unit 108 is detected (step S84—Yes), the seventh internal counter value is not “0”, that is, the time limit for adjusting the irradiation light amount of the density sensor 202 (step S85). -No), a digital value (data) corresponding to the output value of the density sensor 202 is acquired (step S86), and it is determined whether or not the reflectance of the detected uniform reflection region is within an appropriate range (appropriate level). (Step S87).

  If the determination result is within the appropriate range (step S87-Yes), the first internal counter value is incremented (+1) (step S90), and the first internal counter value and the PWM on-duty are increased. The value is written into the RAM 102 (step S91). At this time, since the uniform reflection area is still detected by the density sensor 202, it waits for the detection by the density sensor 202 to deviate from the uniform reflection area (step S92-No).

When it is detected by the density sensor 202 that it has deviated from the uniform reflection region (step S92-Yes), it is determined whether or not the next appearing mark has a specific reflectance, that is, a predetermined threshold value or higher (highest reflectance = white). (Step S93). If the determination result is not a specific reflectance (step S93-No), it waits for an interrupt from the reflectance detection unit 108 until the density sensor 202 detects the next uniform reflection region (step S84-No).
Thereafter, each time the uniform reflection area is detected by the density sensor 202, the value of the first internal counter value and the PWM on-duty value are written in the RAM 102 (step S84-Yes to step S93).

Here, the case where the influence of the eccentricity of the rotating disk 201 reaches the data acquired by the density sensor 202 will be described.
When the CPU 101 detects an interrupt from the reflectance detection unit 108 (step S84—Yes), the seventh internal counter value is not “0”, that is, the time limit for adjusting the irradiation light amount of the density sensor 202 (step S84). (S85-No), a digital value corresponding to the output value of the density sensor 202 is acquired (step S86), and it is determined whether or not the detected reflectance of the uniform reflection region is within an appropriate range (step S87).

If the determination result is not within the appropriate range (step S87-No), the density sensor is changed by changing the on-duty of the PWM by a predetermined width depending on whether the detected reflectance is higher or lower than the appropriate level. The amount of irradiation light 202 is changed (step S88), and the seventh internal counter value is incremented (+1) (step S89).
Then, it is confirmed that the seventh internal counter value is not “0”, that is, it is not the time limit for adjusting the irradiation light quantity of the density sensor 202 (step S85—No), and the digital corresponding to the output value of the density sensor 202 is obtained. A value is acquired again (step S86), and it is determined whether or not the detected reflectance of the uniform reflection region is within an appropriate range (step S87).

If the determination result still does not reach the appropriate range (step S87-No), the irradiation light quantity of the density sensor 202 is changed by further changing the PWM on-duty by a predetermined width (step S88). The seventh internal counter value is incremented (+1) (step S89).
If the reflectance of the uniform reflection area detected within the time limit for adjusting the irradiation light amount of the density sensor 202 can be kept within the appropriate range by repeating this processing loop (step S87-Yes), the first internal The counter value is incremented (+1) (step S90), and the first internal counter value and the PWM on-duty value are written in the RAM 102 (step S91).

  On the other hand, if the seventh internal counter value becomes “0” during the processing loop, that is, if the time limit for adjusting the irradiation light quantity of the density sensor 202 occurs (step S85—Yes), the process ends abnormally. In this case, the process shifts to an error processing routine (not shown) to notify the abnormal state (device diagnosis abnormality). For example, the abnormal state is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).

  Further, the first internal counter value and the PWM on-duty value are written into the RAM 102 (step S91), and it is detected that the detection by the density sensor 202 has deviated from the uniform reflection region (step S92-Yes). When the appearing mark has a specific reflectance, that is, a predetermined threshold value or higher (highest reflectance = white) (Yes in step S93), it means that the rotating disk 201 has made one rotation, and the first front Terminate processing normally.

Next, the second preprocessing of FIG. 29 will be described.
The CPU 101 first initializes the internal counter (step S51). In other words, the fifth internal counter value (Count5) is used for counting the number of times of increasing the irradiation light amount of the density sensor 202, and the sixth internal counter value (Count6) is used for counting the number of times of decreasing the irradiation light amount of the density sensor 202. And set to a specified value (initial value) for determining the first abnormal end.
Next, the drive motor 32 to be measured is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107 (step S1). The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates.

Next, it is checked whether or not there is an interruption from the reflectance detection unit 108 (step S2).
Here, the reflected light from the density pattern formed on the outer peripheral surface of the rotating disk 201 detected by the density sensor 202 is input to the reflectance detection unit 108 as an analog potential while sequentially changing. The reflectance detection unit 108 converts the analog potential from the density sensor 202 into a digital value by the ADC 114 and outputs the digital value. When the digital value is equal to or greater than a predetermined threshold, that is, the reflection detected using the density sensor 202. When the rate is a specific reflectivity (the highest reflectivity), an interrupt is generated for the CPU 101 (step S2-Yes).

When the CPU 101 receives an interrupt from the reflectance detection unit 108 (when the reflectance detected using the density sensor 202 is a specific reflectance), the CPU 101 changes the output value of the density sensor 202 from the reflectance detection unit 108. A corresponding digital value (reflectance detected using the density sensor 202) is acquired, and the digital value is written in the RAM 102 as an initial value (step S3).
Subsequently, the first internal counter value is cleared to “0”, and the third internal counter value and the fourth internal counter value are set to specified values (step S4).

  Here, as described in the first preprocessing, the first internal counter value corresponds to the number of activations of the timer 110, that is, the number of acquisitions of the output value of the density sensor 202, and an identifier for writing and reading data in the RAM 102. It is intended to be used as The third internal counter value is the number of times that the data obtained by the density sensor 202 is determined to be lower than the predetermined value, and the fourth internal counter value is determined that the data obtained by the density sensor 202 is higher than the predetermined value. It is used for counting the number of times to perform, and is set to a specified value (initial value) for determining the second abnormal end.

The CPU 101 activates the timer (period timer) 110 to start time measurement from “0”, increments the first internal counter value (+1), and waits for an interrupt from the reflectance detection unit 108 or the timer 110. It becomes.
When an interrupt from the timer 110 is detected (step S8—Yes), an average data acquisition process is executed (step S9).
Here, the subroutine of the average data acquisition process of FIG. 30 will be described.

The CPU 101 first reads the PWM on-duty value corresponding to the first internal counter value from the RAM 102 (step S101), and determines the irradiation light quantity of the density sensor 202 by setting the read PWM on-duty value to the read PWM on-duty value. (Set) (step S102).
Next, a digital value corresponding to the output value of the density sensor 202 is acquired as the first data (step S41), a prescribed value is set in the second internal counter value (step S42), and a timer (sampling timer) 116 is started and time measurement is started from “0” (step S43), and an interrupt waiting state from the timer 116 is entered (step S44—No).

Here, the product of the second internal counter value (specified value) and the set period of the timer 116 corresponds to the width for performing the averaging process on the density pattern formed on the outer peripheral surface of the rotating disk 201. become.
When the CPU 101 detects an interrupt from the timer 116 (step S44—Yes), the CPU 101 acquires a digital value corresponding to the output value of the density sensor 202 as second data (step S45).

Next, the second internal counter value is decremented (−1) (step S46), and if the second internal counter value is not “0” (step S47—No), the timer 116 is started again and “ Time measurement is started again from "0" (step S43), and the state again waits for an interrupt from the timer 116 (step S44-No).
In this way, the digital value (data) corresponding to the output value of the density sensor 202 for the specified value (specified number of times) set as the second internal counter value is acquired, and the second internal counter value is “0”. (Step S47-Yes), the average value of the acquired digital values for the specified number of times is calculated (Step S48). Thus, the process exits from the average data acquisition process subroutine and returns to the second pre-process main routine of FIG.

  When the CPU 101 returns to the main routine of the second preprocessing, the average value of the digital value corresponding to the output value of the density sensor 202 calculated in the subroutine of the average data acquisition process and the initial value (immediately before writing) in the RAM 102 in step S3. (Step S10), the difference data is written in the RAM 102 together with the first internal counter value (step S11), and if the first internal counter value is “1” (step S52). -Yes) In order to acquire a digital value (data) corresponding to the next output value of the density sensor 202, the timer 110 is restarted and time measurement is started again from "0" (step S5). The internal counter value is incremented (+1) (step S6), and a state of waiting for an interrupt from the reflectance detection unit 108 or the timer 110 is again performed. Made (step S7-No, step S8-No).

Thereafter, the average of the digital value corresponding to the output value of the density sensor 202 and the average of the digital value corresponding to the output value of the density sensor 202 acquired by the previous first internal counter value for each interrupt period of the timer 110. The difference with the value is calculated, and the difference data is written in the RAM 102 together with the first internal counter value (step S8—Yes to step S11).
When the first internal counter value is not “1” (step S52—No), reflectance offset detection processing (see FIG. 24) is executed (step S53).

  Thereafter, the result of the reflectance offset detection process is determined by referring to the adjustment flag. That is, when the irradiation light quantity of the density sensor 202 is not changed in the subroutine of the reflectance offset detection process, the adjustment flag is not set (step S54-No), and therefore corresponds to the next output value of the density sensor 202. In order to obtain the digital value, the process returns to step S5, the timer 110 is restarted, the time measurement is started again from “0”, the internal counter value is incremented (+1) (step S6), and the reflectance detection is performed again. Waiting for an interrupt from the unit 108 or the timer 110 (step S7-No, step S8-No).

Then, when an interrupt from the reflectance detection unit 108 is received again (step S7—Yes), it means that the rotating disk 201 has made one rotation, and thus the second preprocessing is normally terminated.
In this way, a digital value (data) for one rotation of the rotating disk 201 can be stored in the RAM 102. When the acquisition of necessary data (digital value for one rotation of the rotating disk 201) is completed, the data is transferred to the EEPROM 111 to be written and stored.

  When the irradiation light amount of the density sensor 202 is changed in the subroutine of the reflection offset detection process, since the adjustment flag is set (step S54-Yes), the fifth internal counter value or the sixth internal counter value is set. It is determined whether it is “0” (steps S55 and S56).

  When either the fifth internal counter value or the sixth internal counter value is “0” (step S55—Yes or step S56—Yes), the first normal end is performed. In this case, even if the irradiation light quantity of the density sensor 202 is increased / decreased a predetermined number of times, the obtained data does not fall within the normal range, that is, “a light emitting diode or light detection unit that is a light irradiation unit of the density sensor 202. It is determined that the phototransistor is in an abnormal state. Then, the abnormal state (device diagnosis abnormality) is notified by an error processing routine (not shown). For example, the abnormal state is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).

  If neither the fifth internal counter value nor the sixth internal counter value is “0” (step S55-No, step S56-No), the adjustment flag is reset (step S57), and the second It ends abnormally. In this abnormality, the irradiation light amount adjustment data with respect to the rotation angle of the rotating disk 201 acquired in the first preprocessing, that is, the PWM on-duty value corresponding to the first internal counter value executes the second preprocessing. In some cases, it was out of expectation, but normal data can be acquired by readjustment. That is, there is a possibility that some deviation occurs in the density sensor 202 or the rotating disk 201 between the first preprocessing and the second preprocessing. Therefore, in this case, the first pre-processing is performed again to determine abnormality (step S85).

Finally, main control in the fifteenth embodiment (control related to detection of fluctuations in the rotational speed of the rotating disk 201) will be described again with reference to FIG.
During the image forming process, first, the drive motor 32 to be measured is driven via the I / O control unit 104, the drive motor I / F 106, and the driver 107 (step S21). The drive of the drive motor 32 is transmitted in the order of the drive roller 63, the transfer conveyance belt 60, and the lower right roller 66, and the rotary disk 201 attached to the shaft of the lower right roller 66 rotates.

Next, it is checked whether or not there is an interruption from the reflectance detection unit 108 (step S22). When an interruption from the reflectance detection unit 108 is accepted (the reflectance detected using the density sensor 202 is a specific reflectance). The digital value corresponding to the output value of the density sensor 202 (reflectance detected using the density sensor 202) is obtained from the reflectance detection unit 108, and the digital value is written in the RAM 102 as an initial value ( In step S23, the first internal counter value is cleared to “0” (step S24).
Next, the timer (period timer) 110 is activated to start time measurement from “0” (step S25), the internal counter value is incremented (+1) (step S26), and the reflectance detector 108 or timer 110 is incremented. (Step S27-No, Step S28-No).

When an interruption from the timer 110 is detected, an average data acquisition process (see FIG. 30) is performed (step S26), and an average value of digital values corresponding to the output value of the density sensor 202 calculated in the process is calculated in step S23. A difference from the initial value (immediate value) written in the RAM 102 is calculated (step S30).
Next, preprocess data (difference data acquired in the second preprocess) corresponding to the internal counter value (initially “1”) at that time is read from the EEPROM 111 (step S31) and compared with the previously calculated difference data. If the comparison result is less than the predetermined threshold value, it is determined that there is no fluctuation in the rotational speed of the rotating disk 201, that is, no fluctuation in the rotational speed of the transfer conveyance belt 60, and the process returns to step S25.

Then, the timer 110 is restarted to start time measurement again from “0” (step S25), the internal counter value is incremented (+1) (step S26), and again from the reflectance detector 108 or the timer 110. An interrupt wait state is entered (step S27-No, step S28-No).
Thereafter, the average of the digital value corresponding to the output value of the density sensor 202 and the average of the digital value corresponding to the output value of the density sensor 202 acquired by the previous first internal counter value for each interrupt period of the timer 110. A difference from the value is calculated, and the difference data and the corresponding preprocess data are sequentially compared using the first internal counter value as an identifier (steps S25 to S32).

If the comparison result is equal to or greater than a predetermined threshold value, it is determined that the rotation speed of the rotary disk 201, that is, the rotation speed of the transfer conveyance belt 60 has fluctuated, and the process proceeds to an error processing routine (not shown) to notify the determination result. To do. For example, the determination result is sent to the external device 120 to be displayed on the display or displayed on an operation unit (not shown).
Further, if the rotating disk 201 makes one rotation in a state where there is no change in the rotating speed of the rotating disk 201, that is, no change in the rotating speed of the transfer conveyance belt 60, an interrupt from the reflectance detection unit 108 is accepted again (step S27). . In this case, a digital value corresponding to the output value of the density sensor 202 is acquired, reset as an initial value in the RAM 102 (step S23), and the internal counter value is cleared to “0” (step S24).

  Thus, in the fifteenth embodiment, in the belt driving device 6 in the fourteenth embodiment, the density sensor 202 detects a specific reflectance of the density pattern formed on the outer peripheral surface of the rotating disk 201 during the preprocessing. Then, the reference position of the rotation angle of the rotating disk 201 is determined, and the reflectance of the uniform reflectance region for one rotation of the rotating disk 201 is obtained from the reference position by the density sensor 202. The irradiation light amount is adjusted and the adjustment data is held in the RAM 102, and transferred and conveyed while varying the irradiation light amount of the density sensor 202 by the irradiation light amount adjustment data of the density sensor 202 for one rotation of the rotating disk 201 during the image forming process. The fluctuation of the rotation speed of the belt 60 is detected.

According to the fifteenth embodiment, when the irradiation light amount of the density sensor 202 is increased, an offset is generated in which the output value of the density sensor 202 does not change even if the reflectance of the density pattern changes, and the irradiation light amount of the density sensor 202 is reduced. In this case, when the eccentricity of the rotating disk 201 occurs, the amount of irradiation light of the density sensor 202 is optimal with respect to the eccentricity of the rotating disk 201 with respect to the problem that the linearity of the output transition of the density sensor 202 is impaired. Therefore, even when the eccentricity of the rotating disk 201 occurs, it is possible to perform good control without impairing the linearity of the output transition of the density sensor 202.
Furthermore, the process of acquiring the adjustment data of the irradiation light quantity of the density sensor 202 and the process of adjusting the irradiation light quantity of the density sensor 202 are separated, and the processing tasks in the image forming process that the CPU 101 is most busy with can be reduced. It becomes possible.

In the above-described embodiment, the lower right roller 66 of the driven rollers that are driven to rotate by the rotation of the transfer conveyance belt is used as the target roller. It may be a roller.
As described above, the embodiment in which the present invention is applied to the drive control device (belt drive device) for driving and controlling the transfer conveyance belt has been described. The present invention can also be applied to a drive control device that drives and controls a body belt, a transfer belt, an intermediate transfer belt, or an image recording medium transport belt.

In other words, all of the above-described embodiments are applied to a belt driving device (including a drive control device) in a tandem laser printer in which a plurality of photosensitive drums 11Y, 11M, 11C, and 11K are arranged on the transfer conveyance belt 60. Although the example to which the present invention is applied has been described, the image forming apparatus and the belt driving apparatus to which the present invention is applicable are not limited to this configuration.
An image forming apparatus having a driving device that rotationally drives an endless moving member by one or more rollers, such as a belt driving device that rotationally drives an endless belt stretched around a plurality of rollers by at least one of the rollers. If so, the present invention can be applied to any of the driving devices.

Furthermore, in the above-described embodiment, the present invention is applied to a direct transfer type color printer that transports transfer paper by a transfer transport belt and sequentially transfers four color toner images from the photosensitive drum on the transfer paper. The present invention is also applied to a driving device in an indirect transfer type color printer that transfers four color toner images onto an intermediate transfer belt or an intermediate transfer drum, and after the four colors are superposed, is transferred to a transfer sheet at once. Is possible.
Furthermore, although laser light is used as the exposure light source in the above-described embodiment, the present invention is not limited to this. For example, an LED array or the like may be used as the light source.

As is clear from the above description, according to the rotational speed fluctuation detecting device of the present invention and the drive control device having the same, the rotational speed fluctuation of the endless moving member can be accurately and efficiently performed without using a general encoder. It can be detected well. Therefore, if this invention is utilized, the rotational speed fluctuation | variation detection apparatus which can detect the rotational speed fluctuation | variation of an endless moving member correctly and efficiently, and a drive control apparatus which has it can be provided.
According to the image forming apparatus of the present invention, by using the drive control device, appropriate image formation can be performed and the image quality can be improved. Therefore, if this invention is used, an image forming apparatus capable of acquiring a high-quality image can be provided.

It is a perspective view which shows the 1st example of the principal part structure of the belt drive device 6 at the time of making the lower right roller 66 of FIG. 3 into an object roller. 1 is a schematic configuration diagram of an entire laser printer showing an example of an image forming apparatus provided with a belt drive device including a drive control device according to the present invention. It is an enlarged view which shows schematic structure of these. FIG. 5 is a perspective view showing the configuration of the conventional transfer conveyance belt 60 in the belt driving device 6 as seen through.

FIG. 5 is a perspective view showing details of a lower right roller 66 and an encoder 31 shown in FIG. 4. FIG. 6 is a diagram for explaining a state where the rotary disk 201 in the encoder 31 shown in FIG. 5 is not eccentric (original state) and an eccentric state. FIG. 5 is a diagram showing different examples of sampling results when the drive motor 32 of FIG. 4 is driven at a constant speed and the count value of the output pulse of the encoder 31 is sampled at a constant timing. It is a block diagram which shows the hardware structural example of the control part containing the drive motor control part of the belt drive device 6 in the laser printer shown in FIG.

FIG. 4 is an explanatory diagram showing a first development example of a part of the rotating disk 201 attached to the shaft of the lower right roller 66 of FIG. 3 and a pattern on the outer peripheral surface thereof. It is a flowchart which shows the 1st example of the pre-processing by CPU101 of FIG. It is a flowchart which similarly shows the 1st example of main control. FIG. 9 is a timing chart showing an example of a different interrupt cycle of the timer 110 with respect to the output value of the density sensor 202 of FIG. 8. FIG. 9 is a diagram illustrating an example of a relationship between an internal counter value and an output value of a density sensor 202 during pre-processing and main control by the CPU 101 in FIG. 8.

It is a block diagram which shows the other hardware structural example of the control part containing the drive motor control part of the belt drive device 6 in the laser printer shown in FIG. It is a flowchart which shows the 2nd example of the pre-processing by CPU101 of FIG. It is a flowchart which similarly shows the 2nd example of main control. It is a flowchart which shows an example of the subroutine of the average data acquisition process in FIG. 15 and FIG. FIG. 4 is an explanatory diagram showing a second development example of a part of the rotating disk 201 attached to the shaft of the lower right roller 66 of FIG. 3 and the pattern of the outer peripheral surface thereof.

FIG. 4 is a perspective view showing the configuration of a transfer conveyance belt 60 in the belt driving device 6 when the lower right roller 66 in FIG. 3 is a target roller. It is a front view for demonstrating the example from which the principal part structure of the belt drive device 6 at the time of making the lower right roller 66 of FIG. 3 into an object roller differs. FIG. 6 is a perspective view showing a second example of the main configuration of the belt driving device 6. FIG. 10 is a block diagram showing still another hardware configuration example of a control unit including a drive motor control unit of the belt driving device 6 in the laser printer shown in FIG. 2.

It is a flowchart which shows the 3rd example of the pre-processing by CPU101 of FIG. It is a flowchart which shows an example of the subroutine of the reflectance offset detection process in FIG. The density pattern formed on the outer peripheral surface of the rotary disk 201 attached to the shaft of the lower right roller 66 in the belt driving device 6 when the lower right roller 66 in FIG. FIG. 6 is a timing chart showing an example of the relationship between the output value of the density sensor 202 and time in the case of being performed. It is explanatory drawing which shows the 3rd example of a pattern of a part of lower right roller 66 of FIG. 3, and its outer peripheral surface.

FIG. 27 is a timing chart showing an example of the relationship between the output value of the concentration sensor 202 of FIG. 26 and time. FIG. 23 is a flowchart showing first preprocessing (fourth example of preprocessing) by the CPU 101 of FIG. 22. It is a flowchart which similarly shows 2nd pre-processing (5th example of pre-processing). It is a flowchart which shows an example of the subroutine of the average data acquisition process in FIG.

Explanation of symbols

1Y, 1M, 1C, 1K: toner image forming unit 6: belt driving device 32: driving motor 60: transfer conveying belt 63: driving roller 66: lower right roller (driven roller)
100: Control unit 101: CPU 102: RAM 103: ROM
104: I / O control unit 106: Drive motor I / F 107: Driver 108: Reflectance detection unit 109: CPU bus 110, 116: Timer 111: EEPROM 202: Density sensor 203: Flywheel 204: Cleaning member

Claims (6)

A rotational speed fluctuation detecting device for detecting a rotational speed fluctuation of a rotating disk,
The rotating disk is a pattern in which the reflectance varies depending on the position of the outer circumferential surface in the circumferential direction, and is formed along the circumferential direction.
Reflectance detection means for detecting the reflectance of the pattern;
Data acquisition means for acquiring the reflectance data detected by the reflectance detection means every predetermined time while the rotating disk makes one rotation at a constant speed in advance, and writing it to the memory;
Fluctuation detecting means is provided for detecting the fluctuation of the rotational speed of the rotating disk by acquiring the reflectance data detected by the reflectance detecting means at the time of measurement every predetermined time and comparing it with the data in the memory. A rotational speed fluctuation detecting device characterized by that. A rotational speed fluctuation detecting device for detecting a rotational speed fluctuation of a rotating disk,
The rotating disk is a pattern in which the reflectance varies depending on the position of the outer circumferential surface in the circumferential direction, and is formed along the circumferential direction.
Reflectance detection means for detecting the reflectance of the pattern;
The reflectance data detected by the reflectance detection means is acquired and stored every predetermined time in advance while the rotating disk rotates once at a constant speed, and the previously stored reflectance data and this time are stored each time. Data acquisition means for writing difference data with the reflectance data into the memory;
Reflectance data detected by the reflectance detection means during measurement is acquired and stored every predetermined time, and each time difference data between the reflectance data stored last time and the reflectance data stored this time is obtained. A rotation speed fluctuation detecting device, comprising: fluctuation detecting means for detecting fluctuations in the rotation speed of the rotating disk by comparing with difference data in the memory. In the rotation speed fluctuation detection device according to claim 1 or 2,
The rotational speed fluctuation detecting apparatus according to claim 1, wherein the pattern is composed of a plurality of marks each having a different reflectance. A drive control device comprising the rotational speed fluctuation detection device according to any one of claims 1 to 3,
A driving roller for rotating the endless moving member or a driven roller that is rotated by the rotation of the endless moving member is attached to the rotating disk, and a driving source for rotating the driving roller;
A drive control device comprising: control means for drivingly controlling the drive source based on a rotational speed variation of the rotating disk detected by the rotational speed variation detection device.   An image forming apparatus comprising the drive control device according to claim 4, wherein the endless moving member is an endless moving member for image formation. The image forming apparatus according to claim 5, wherein
An image forming apparatus, wherein the endless moving member for image formation is any one or more of a photosensitive belt, a transfer belt, an intermediate transfer belt, and an image recording medium transport belt.