JP2007327912A - Relative position detection device/belt conveyance device/image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relative position detection device capable of suppressing variations in sensor interval (changes in observation position) with time caused by temperature etc., and capable of performing detection with high accuracy. <P>SOLUTION: The relative position detection device 25 has a scale 21 having optical marks formed at approximately constant intervals, and a head section 22. The head section 22 is composed of light sources 26, 27, slits 28a, 28b as light shaping means for shaping rays of light from the light sources 26, 27 and generating light beams for irradiating the scale 21, and photodetectors 29, 30 for receiving the light beams having passed through optical marks of the scale 21. The slits 28a, 28b are formed on the same member, masking the surface of a synthetic quartz glass plate 31 having a low coefficient of linear expansion with a vapor deposited film 32 of chromium or the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a relative position detecting device for optically detecting a scale, a belt conveying device having the same, a copier, a printer, a facsimile having the relative position detecting device or the belt conveying device, and at least two of them. The present invention relates to an image forming apparatus such as a multifunction peripheral or a plotter having a function.
The present invention can be used in a moving amount measurement and control system for a rotating body in an image forming apparatus including a rotating body for image formation such as a photosensitive belt, a transfer belt, a paper conveying belt, a photosensitive drum, and a transfer drum.

2. Description of the Related Art Conventionally, an image forming apparatus including a rotating body for image formation such as a photosensitive belt or an intermediate transfer belt has been widely used. In such an image forming apparatus, the rotation amount (movement amount) of the rotating body is accurately controlled in order to perform high-precision image alignment on the rotating body and on the transfer material conveyed by the rotating body. Is required.
However, the amount of rotation of the rotator often fluctuates for some reason, and it is difficult to suppress image position errors. In particular, in a color image forming apparatus, there is a problem in that due to a change in the amount of rotation of a rotating body, an image does not overlap at a position that should originally overlap and a positional shift occurs between colors.

Also, in the image forming apparatus, speed fluctuations (variations in the amount of rotation) of a rotating body such as a photosensitive belt or an intermediate transfer belt are caused by fluctuations in belt thickness, roller eccentricity, and drive motor speed irregularities. End up.
In particular, in the color image forming apparatus, as shown in FIG. 17, the positioning error due to the belt speed fluctuation becomes a waveform having a plurality of frequency components. The image formed by superimposing the toner images during the belt speed fluctuation is an image in which the positions of the colors are not aligned. Therefore, the belt speed fluctuation causes image quality deterioration such as color shift and color change.

In order to suppress image position errors due to fluctuations in the speed of the rotating body, a rotary encoder is directly connected to the rotating shaft of the driving roller that drives the rotating body and other rotating shafts, and the rotational angular velocity of the rotating body detected by this encoder is adjusted. An image forming apparatus that controls the rotational angular velocity of a drive motor based on this has been proposed (see Patent Document 1).
However, such an image forming apparatus can only indirectly control the rotation amount (movement amount) of the rotating body by controlling the rotational angular velocity of the drive motor, and accurately controls the rotation amount. It is difficult.

A technique is disclosed in which a mark is formed on the surface of a belt, which is a rotating body, and a belt surface speed is calculated from a pulse interval obtained by detecting the mark with a sensor to feedback control the amount of rotation of the belt ( (See Patent Document 2 and Patent Document 3).
According to such a technique, since the behavior of the belt surface can be directly observed, the rotation amount (movement amount) of the belt can be directly controlled.

However, in general, a belt used for an application such as an image forming apparatus has flexibility, thickness deviation, and deformability. As a result, the pattern period of the mark formed on the belt surface changes, and there is a problem that accurate position information cannot be obtained even if the mark is measured with high accuracy.
As a method of measuring the surface position with high accuracy even if there is an error in the belt mark pitch, two sensors are arranged, and from the time difference t for detecting the same mark and the sensor interval D, V = D / t
As a method, a method for obtaining the speed has been proposed (see Patent Document 4).
According to this method, since the time during which the same mark moves is observed, the mark interval error is unlikely to be a measurement error.

JP-A-6-175427 JP-A-6-263281 JP-A-9-114348 Japanese Patent No. 3344614

However, in the method disclosed in Patent Document 4, since the speed is calculated with the sensor interval D as an absolute reference, it is influenced by the error of D.
As a countermeasure against this, Patent Document 4 discloses the measurement of the difference in time detected by the sensor over a predetermined period, obtains the average value of the passing time, and after determining the average value, It is disclosed that the conveying speed of the belt surface is detected by comparing the average values, and the drive motor is controlled so that the detected conveying speed is constant.
However, in this case, the accuracy over time of the two sensor intervals becomes important. That is, if the interval between two sensors changes due to a change in the environment, the measured transit time changes. As a result, a speed measurement error is generated by an amount corresponding to the sensor interval error, leading to deterioration of the output image.

The specification of Patent Document 4 states that “the rotational speed of the driving source is based on the recognition that the fluctuation of the predetermined speed is limited to within a few percent of the comma, and the average speed is 0.00% from the predetermined speed. Although only an error is included, ”a color image forming apparatus has a 0. A few percent is a very large number in the case of a tandem color machine. For example, when the photosensitive roller pitch is 150 mm, 0.1% corresponds to a deviation of 0.15 mm, so color misregistration is clearly recognized. It becomes the level that can be done.
The same can be said for the case where the interval between the two sensors changes due to a temperature change, and it can be seen that a change in the sensor interval causes a large error.

It is an object of the present invention to provide a relative position detection device that can suppress sensor interval fluctuation (change in observation position) due to temperature or the like, and an image forming apparatus that has the relative position detection device and can output a high-quality color image. To do.
In addition, even if an error occurs in the mark pitch, the belt surface linear velocity can be accurately detected, and a belt conveyance device capable of obtaining high accuracy conveyance by feedback control, and a high accuracy color having the belt conveyance device. An object of the present invention is to provide an image forming apparatus capable of outputting an image.

  In order to achieve the above object, according to the first aspect of the present invention, a scale in which marks are formed at substantially constant intervals, and a light beam is irradiated onto the scale, and light reflected or transmitted by the marks is received. In a relative position detection device that has a head section that performs photoelectric conversion and detects a relative position change between the scale and the head section, the head section is a light source and light that shapes the light from the light source and irradiates the scale A light shaping unit that generates a beam; and a light receiving member that receives the light beam that has passed through the mark, and emits a plurality of light beams having different positions in a relative movement direction of the scale and the head unit, The light receiving member photoelectrically converts the plurality of light beams into separate electric signals, and the light shaping means is formed on the same member.

According to a second aspect of the present invention, in the relative position detection device according to the first aspect of the present invention, a correction for generating a relative position signal in which the mark spacing error is corrected based on a plurality of detection signals from the plurality of light beams. It has an operation part.
According to a third aspect of the present invention, in the relative position detection device according to the first or second aspect, the light shaping means is formed of a material having a low linear expansion coefficient.

According to a fourth aspect of the present invention, in the relative position detecting device according to the third aspect, the material having a low linear expansion coefficient is a glass material.
According to a fifth aspect of the present invention, in the relative position detection device according to any one of the first to fourth aspects, the light shaping means is a plurality of slit rows.
According to a sixth aspect of the present invention, in the relative position detection device according to the fifth aspect, the light beam incident on the light shaping means has a larger beam diameter than the light passage region of the slit row. .

According to a seventh aspect of the present invention, in the relative position detection device according to any one of the first to sixth aspects, the light beam incident on the light shaping means has a uniform light amount distribution.
According to an eighth aspect of the present invention, in the relative position detection device according to any one of the first to seventh aspects, a gap adjusting member that maintains a constant gap between the scale and the head portion is provided. Features.
According to a ninth aspect of the present invention, in the relative position detecting device according to the eighth aspect of the present invention, the light shaping means is configured integrally with the gap adjusting member.

According to a tenth aspect of the present invention, the belt conveyance device includes the relative position detection device according to any one of the first to ninth aspects.
According to an eleventh aspect of the present invention, the image forming apparatus includes the belt conveyance device according to the tenth aspect.
According to a twelfth aspect of the present invention, in the relative position detecting device according to any one of the first to ninth aspects, the scale is formed by forming the marks radially on a disk substrate. .
According to a thirteenth aspect of the present invention, the image forming apparatus includes the driving device including the relative position detection device according to the twelfth aspect.

According to the present invention, since the scale mark pitch is corrected and the relative position change between the scale and the head is observed, even if an error occurs in the scale mark pitch, the position can be detected with high accuracy. High image quality can be achieved.
In addition, since the two light shaping means are formed on the same member, the observation position can be maintained with high accuracy over time, so the absolute value of the mark pitch error can be obtained from the phase of the two signals. In the image forming apparatus, high image quality can be realized.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, the outline of the configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG. The image forming apparatus 1 includes a plurality of electronic processes in order from the upstream side in the rotation direction (conveyance direction) of the conveyance belt 3 along a conveyance belt 3 that is a rotating body that conveys transfer paper 2 as a recording medium. The units 1K (black), 1M (magenta), 1Y (yellow), and 1C (cyan) are arranged. The image forming apparatus 1 is a so-called tandem type color image forming apparatus.

  The plurality of electronic process units 1K, 1M, 1Y, and 1C function as image forming units. The electronic process unit 1K forms black, the electronic process unit 1M forms magenta, the electronic process unit 1C forms cyan, and the electronic process unit 1Y forms yellow images. The electronic process units 1K, 1M, 1Y, and 1C have the same internal configuration except that the colors of images to be formed are different. In the following description, the electronic process unit 1K will be described in detail. However, for the other electronic process units 1M, 1Y, and 1C, M, Y, C, and the like are used instead of the component K related to the electronic process unit 1K. This is indicated in the figure with the symbol.

  One end of the transport belt 3 is a driving roller 4 that is driven to rotate, and the other endless belt is an endless belt that is rotatably supported by transport rollers 4 and 5 that are driven rollers 5 that are driven to rotate. 1 and is configured to rotate in the direction of the arrow in FIG. 1 along with the rotation of the transport rollers 4 and 5. A sheet feeding tray 6 in which the sheet 2 is stored is provided below the conveying belt 3. Of the sheets 2 stored in the sheet feeding tray 6, the sheet 2 at the uppermost position is sent out at the time of image formation and is attracted to the transport belt 3 by electrostatic attraction. The sheet 2 adsorbed on the conveyor belt 3 is conveyed to the first electronic process unit 1K, where a black image is transferred.

  The electronic process unit 1K includes a photosensitive drum 7K as an image carrier, and a charger 8K, an exposure unit 9K, a developing unit 10K, a photosensitive cleaner 11K, and the like disposed around the photosensitive drum 7K. . A laser scanner is used as the exposure device 9K. The laser scanner reflects a laser beam from a laser light source (not shown) by a polygon mirror, and passes through an optical system (not shown) using an fθ lens, a deflection mirror, or the like. Is emitted.

  At the time of image formation, the peripheral surface of the photosensitive drum 7K is uniformly charged by the charger 8K in the dark, and is then exposed to the exposure light 12K corresponding to the black image from the exposure device 9K. Exposure is performed to form an electrostatic latent image. The electrostatic latent image is visualized with black toner in the developing device 10K, and a black toner image is formed on the photosensitive drum 7K.

  This toner image is transferred onto the sheet 2 by the action of the transfer unit 13K at a position where the photosensitive drum 7K and the sheet 2 on the conveying belt 3 are in contact with each other, so-called transfer position. It is formed. After the transfer, unnecessary toner remaining on the peripheral surface of the photoconductive drum 7K is removed by the photoconductive cleaner 11K to prepare for the next image formation.

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

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

FIG. 6 is an external perspective view schematically showing the belt conveyance device 15 having the conveyance belt 3.
The conveyor belt 3 is stretched over the driving roller 4 and the driven roller 5 and has a scale 21 at its end. The scale 21 includes a reflection mark 21a as a plurality of marks (also referred to as optical marks) arranged alternately in the rotation direction of the conveyance belt 3 (the movement direction of the circumferential surface of the conveyance belt 3), and a plurality of slits or The transmission part 21b is comprised. The reflection mark 21a and the transmission part 21b are provided with a mark period which is a predetermined periodic pattern.

  In the present embodiment, the transmission part 21b functions as a mark. When detecting the light reflected from the reflective mark 21a, the reflective mark 21a also functions as a mark. That is, the mark may be a mark whose reflectance or transmittance changes, and may be a printed pattern having a different color such as white or black, or a total reflection pattern such as an aluminum vapor deposition film. Such reflection marks 21a and slits 21b cause a single or continuous reflectance change depending on the number thereof.

  The transmission part 21 b of the scale 21 is detected by the head part 22. The scale 21 and the head unit 22 constitute a transmission type relative position detection device 25 according to this embodiment. The light emission side of the head unit 22 is provided at a position facing the scale 21 and separated from the transport belt 3 by a predetermined distance (detection distance). Further, the drive roller 4 is connected to a drive motor 24 via a speed reducer 23 and is rotationally driven by a drive force by the drive motor 24.

The relative position detection device 25 will be described in detail with reference to FIG.
As described above, the relative position detection device 25 irradiates the scale 21 with the optical marks formed at substantially constant intervals and irradiates the scale 21 with a light beam, receives light reflected or transmitted by the optical marks, and performs photoelectric conversion. And a configuration for detecting a change in the relative position of the scale 21 and the head unit 22 by changing the amount of received light detected by the relative movement of the scale 21 and the head unit 22. is doing.

Specifically, the head unit 22 includes light sources 26 and 27, slits 28 a and 28 b as light shaping means for shaping the light from the light sources 26 and 27 and generating a light beam that irradiates the scale 21, and the scale 21. It comprises light receiving elements 29 and 30 as light receiving members for receiving a light beam passing through the optical mark. In FIG. 6, the light receiving elements 29 and 30 of the head portion 22 are omitted.
The head unit 22 emits a plurality of light beams (here, the light beam 1 and the light beam 2) having different positions in the relative movement direction of the scale 21 and the head unit 22, and the light receiving elements 29 and 30 receive the plurality of light beams. Are converted into separate electrical signals.
Slits 28a and 28b as light shaping means are formed on the same member. Specifically, as shown in FIG. 4, the surfaces of a synthetic quartz glass plate 31 having a low linear expansion coefficient are masked with a vapor deposition film 32 such as chrome to form slits 28a and 28b.

As the light sources 26 and 27, for example, light emitting diodes (LEDs) are used. However, the present invention is not limited to this, and for example, semiconductor lasers or light bulbs may be used. Since it is preferable to use a light beam with good parallelism, a light source with a small light emitting area such as a semiconductor laser or a point light source LED is preferable. A collimating lens may be used in order to efficiently use light from the light source.
The light receiving elements 29 and 30 may be any element that can convert the intensity of light into an electric signal. For example, a photodiode or a phototransistor is used.

As the light shaping means, in this embodiment, a beam shaping configuration using a fixed mask is shown.
The fixed mask has slits 28a and 28b through which light passes. The slits 28a and 28b are openings formed in a predetermined pattern shape so that the irradiation light applied to the scale 21 has a desired shape.
In the present embodiment, the fixed mask has a plurality of light shaping portions (here, slits) on the same member. Although an example of an aperture slit is shown here, a combination of lens systems may be used as long as it has a function of shaping a beam so as to obtain a beam pattern to be irradiated on the scale.

The light receiving elements 29 and 30 receive the light beams 1 and 2, respectively, and perform photoelectric conversion. Each photoelectrically converted signal is connected to a comparator such as an amplifier or a comparator and digitized, so that the pulse period can be measured by the counter of the position calculation unit as shown in FIG.
The resulting digital signal is as shown in FIG. Here, since the light shaping means 28 is formed on the same member, the positions of the slits 28a and 28b can be determined with high accuracy. For example, if the two slits 28a and 28b are formed at a distance that is an integral multiple of the mark pitch of the scale 21, the two signals obtained are exactly the same phase signal if the mark pitch of the scale 21 is accurate. If there is an error in the mark pitch of the scale 21, a signal having a phase shift is observed.

Data obtained by measuring the pulse period with the counter is sent to the correction calculation unit 33 as shown in FIG. The correction calculator 33 obtains an actual speed obtained by correcting the mark pitch of the scale 21 as shown in the following equation from the pulse period “Ta” and the phase difference “δt” between the two signals.
Reference numerals 34 and 35 in the light shaping unit in FIG. 2 indicate collimating lenses that convert light into parallel luminous fluxes.

It goes without saying that the relative movement distance between the head unit 22 and the scale 21 can be obtained based on the speed data. In the above formula, the sensor means a light receiving element.
In the present embodiment, the description has been given of the case where only two light beams are used. However, the number of light beams is not limited to two, and a configuration using more beams is also possible.
In addition, the method for correcting the mark pitch error of the scale 21 from the phase difference between the two signals has been described, but the speed is calculated from the time when the same mark is observed by the two detectors as in the prior art example. This method can also be applied.

As described above, in this embodiment, since the mark pitch of the scale 21 is corrected and the relative position change between the scale 21 and the head unit 22 is observed, highly accurate position detection can be performed even if an error occurs in the mark pitch of the scale 21. it can.
In addition, since the two light shaping means (slits 28a and 28b) are formed on the synthetic quartz glass plate 31 as the same member, the observation position can be maintained with high accuracy over time, so that the two signal The absolute value of the mark pitch error can be obtained from the phase.
Since the conventional technique uses the average value of the mark pitch of the scale as a reference, the absolute position is unknown.
Furthermore, if the light shaping means is formed of a material having a low linear expansion coefficient, the measurement accuracy can be maintained with high accuracy even if the environment changes. Here, an example in which a chromium vapor deposition film is formed on the synthetic quartz glass plate 31 as a material has been shown, but the combination of materials is not limited thereto. It can be appropriately determined according to the environment to be applied and the required accuracy. If a material with a linear expansion coefficient close to 0 used for a high-precision encoder is used, the accuracy will be very high.

A second embodiment will be described with reference to FIG. Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
The head portion 36 of the relative position detection device according to the present embodiment has a reflective configuration. Therefore, the reflective mark 21a of the scale 21 functions as a mark.
The head unit 36 includes a housing 37. Inside the housing 37, a light emitting element (such as an LED) 38 as a light source, a light projecting lens 39, slits 28 a and 28 b as light shaping means, and light receiving elements 29 and 30 are provided. Has been placed.
In the present embodiment, the light source and the light receiving element are arranged in one casing, but it is also possible to connect two casings that do not have the light shaping means by the light shaping means. Further, the housing itself may be integrated with the light shaping means.

A third embodiment will be described based on FIGS. 8 and 9.
The present embodiment is characterized in that the light shaping means is a plurality of slit rows. As shown in FIG. 8, on the synthetic quartz glass plate 31, light shaping means 40 and 41 each having three slits are formed.
In this way, by using a fixed mask constituted by a plurality of slits, mark detection by a plurality of beams can be performed.
By using a plurality of beams, a plurality of marks on the scale can be observed at the same time, and sensing that is resistant to detection errors due to mark defects and dirt is possible.

Also, as shown in FIG. 9, the light beam incident on the light shaping means 40, 41 is larger than the passage region (x × y region) of the slit row, that is, has a beam diameter large enough to cover this region. ing.
FIG. 9A shows an example when the beam has a smaller beam diameter than the slit row. Even if the light shaping means is made of a material that hardly changes with respect to the environmental change, if the light source and the casing are made of ordinary materials, the beam emission position changes due to the environmental change. For this reason, as shown in FIG. 9A, the position of the beam shifts, and the pattern of the beam passing through the slit also changes, and the scale observation position shifts.

That is, apparently, the interval between the two heads has changed, and high-precision measurement cannot be performed.
On the other hand, as shown in FIG. 9B, when a beam having a diameter of the light beam incident on the light shaping unit is larger than the slit row of the light shaping unit, the incident position of the beam changes depending on the environment. The same pattern will be emitted. It goes without saying that the observed signal does not change unless the beam emission pattern changes.
As described above, the light beam incident on the light shaping means has a larger beam diameter than the passage region of the slit row, so that a relative position measuring apparatus capable of highly accurate measurement can be obtained even when the environment changes.

A fourth embodiment will be described with reference to FIG.
In the present embodiment, the light beam incident on the light shaping means has a uniform light amount distribution.
As described above, a change in the pattern irradiated to the scale 21 causes a measurement error. As shown in FIG. 10A, when the beam has a light quantity distribution, the light intensity distribution in the beam pattern changes when the beam position from the light source changes.
On the other hand, as shown in FIG. 10B, if a beam having a uniform light amount distribution is used, the intensity pattern of the emitted beam does not change even if the beam position changes from the light source.

A fifth embodiment will be described with reference to FIG.
The head portion 34 of the relative position detection device according to the present embodiment has a gap adjusting member (also referred to as a gap holding member) 44 that maintains a constant gap in the light traveling direction with the scale 21 head portion 43.
The slits 28 a and 28 b are configured integrally with the gap adjusting member 44. In order to prevent measurement errors from occurring even when there is an environmental change, it is necessary to prevent the positional relationship between the scale and the light shaping means from changing.
By integrating the gap adjusting member for adjusting the gap between the scale 21 and the head portion 43 and the 44 slit, the positional relationship between the scale 21 and the light shaping means can be maintained with high accuracy.

  The light beam that has passed through the light shaping means is preferably perpendicular to the scale 21 or parallel to a plane whose normal is the direction of movement of the scale 21, but if an error occurs in the beam emission angle, the light shaping means If there is a large gap in the scale, the position of the light beam applied to the scale will shift, and the apparent sensor interval (head portion interval) will shift. In order to eliminate such an error, it is effective to make the gap between the light shaping means and the scale as short as possible.

  As shown in FIG. 12, if an elastic contact material 45 such as a brush, sponge, or felt is used for the gap adjusting member 44, the gap can be adjusted and the scale can be cleaned (sixth embodiment). When applied to an image forming apparatus using toner that is fine particles, adhesion of toner to the scale becomes a problem, and therefore, scale cleaning is useful.

A seventh embodiment will be described with reference to FIG.
A rotary encoder 50 as a relative position detection device according to the present embodiment includes an encoder wheel 51 as a scale and a head unit 52 having a light source unit 53.
In general, low-cost rotary encoders are equipped with two sensor heads at positions facing each other by 180 ° in order to eliminate the cost of adjusting the disc scale mounting eccentricity during assembly. In the embodiment, the scale pitch correction is performed by the adjacent heads, so that the slit pitch error due to the eccentricity is corrected, and the eccentricity correction can be realized with a simple structure.

In the present invention, measurement can be performed while correcting the mark pitch. Therefore, it can be applied to a belt-like traveling body in which expansion and contraction occurs depending on the environment, and a rotating body having a cylindrical surface whose detection height varies and the encoder head cannot be brought close to. It is valid.
FIG. 14 shows an application example to the belt conveyance device 54, and FIG. 15 shows an application example to the belt conveyance device 55. As a control controller, a CPU or a DSP is often used to perform software control. However, since position calculation can also be executed on a program, it can be realized with a simple configuration if commonly used.
In FIG. 14, reference numeral 54 indicates a support roller, in FIG. 15, reference numeral 56 indicates a driving roller, and 57 indicates a driven roller.

The relative position detection apparatus of the present invention can be applied to an electrophotographic apparatus as shown in FIG. In an image carrying means called an intermediate transfer belt in a color electrophotographic apparatus (color image forming apparatus), since a plurality of color images are sequentially superimposed, it is necessary to keep the surface speed of the intermediate transfer belt and the angular speed of the photosensitive drum constant. Is done. It is effective to apply the relative position detecting device of the present invention to the intermediate transfer belt conveying device and the rotary encoder of the present invention to the photosensitive drum rotating device.
Further, when a driving device using the relative position detection device of the present invention is used for paper conveyance and nozzle head control in an inkjet image forming apparatus, a highly accurate output image can be obtained.

An example of the configuration of the color image forming apparatus will be described in detail. In this color image forming apparatus, an apparatus main body 61 is placed on a paper feed table 60. A scanner 62 is mounted on the apparatus main body 61, and an automatic document feeder (ADF) 63 is mounted thereon.
In the apparatus main body 61, a transfer device 65 having an intermediate transfer belt 64 which is a belt-like endless moving member is provided at substantially the center thereof. The intermediate transfer belt 64 includes a driving roller 66 and two driven loafs 67 and 68. It is stretched between them so as to rotate clockwise.

The intermediate transfer belt 64 has a cleaning device 69 provided on the left side of the driven roller 67 so that residual toner remaining on the surface after image transfer is removed.
Above the linear portion spanned between the driving roller 66 and the driven roller 67 of the intermediate transfer belt 64, yellow (Y), cyan (C), magenta (M) along the moving direction of the intermediate transfer belt 64. ), Four drum-shaped photoconductors 70Y, 70C, 70M, and 70K (hereinafter simply referred to as the photoconductor 70 if not specified) of black (K) are arranged at predetermined intervals.
Four primary transfer rollers 71 are provided on the inner side of the intermediate transfer belt 64 so as to oppose the respective photoreceptors 70 and sandwich the intermediate transfer belt 64 therebetween.

Each of the four photoconductors 70 can be rotated counterclockwise. Around each photoconductor 70, a charging device 72, a developing device 73, the above-described primary transfer roller 71, and photoconductor cleaning are provided. An apparatus 74 and a charge removal apparatus 75 are provided, and each constitutes an image forming unit 76. A common exposure device 77 is provided above the four image forming units 76.
Each image (toner image) formed on each photoconductor is directly superimposed on the intermediate transfer belt 64 and sequentially transferred.

On the other hand, on the lower side of the intermediate transfer belt 64, a secondary transfer device 78 serving as a transfer unit that transfers an image on the intermediate transfer belt 64 to a sheet P that is a recording sheet is provided. The secondary transfer device 78 has a secondary transfer belt 80, which is an endless belt, spanned between two rollers 79 and 79. The secondary transfer belt 80 is pressed against the driven roller 68 via the intermediate transfer belt 64. It has come to hit.
The secondary transfer device 78 collectively transfers the toner images on the intermediate transfer belt 64 onto the sheet P fed between the secondary transfer belt 80 and the intermediate transfer belt 64.
A fixing device 81 for fixing the toner image on the sheet P is provided downstream of the secondary transfer device 78 in the sheet conveying direction. A pressure roller 83 is pressed against the fixing belt 82 which is an endless belt.

The secondary transfer device 78 also functions to convey the sheet after image transfer to the fixing device 81. Further, the secondary transfer device 78 may be a transfer device using a transfer roller or a non-contact charger. Below the secondary transfer device 78, a sheet reversing device 84 for reversing the sheet when images are formed on both sides of the sheet is provided.
As described above, the apparatus main body 61 constitutes an indirect transfer tandem color image forming apparatus.
When making a color copy with this color image forming apparatus, the document is set on the document table 85 of the automatic document feeder 63. When the document is manually set, the automatic document feeder 63 is opened, the document is set on the contact glass 86 of the scanner 62, and the automatic document feeder 63 is closed and pressed.

When a start key (not shown) is pressed, when the document is set on the automatic document feeder 63, the document is fed onto the contact glass 86. When the document is manually set on the contact glass 86, the scanner 62 is immediately driven, and the first traveling body 87 and the second traveling body 88 start traveling.
Light is emitted from the light source of the first traveling body 87 toward the document, and the reflected light from the document surface travels toward the second traveling body 88 and the light is reflected by the mirror of the second traveling body 88 to form an image. The light enters the reading sensor 90 through the lens 89 and the content of the original is read.
Further, when the start key is pressed, the intermediate transfer belt 64 starts to rotate. At the same time, the photoconductors 70Y, 70C, 70M, and 70K start rotating, and yellow (Y), cyan (C), magenta (M), and black (K) single-color toner images on the photoconductors. The operation to form is started.
The toner images of the respective colors formed on the respective photoreceptors are sequentially transferred while being superimposed on the intermediate transfer belt 64 that rotates in the clockwise direction, and a full-color composite color image is formed there.

On the other hand, when the start key described above is pressed, the paper feed roller 91 of the selected paper feed stage in the paper feed table 60 rotates, and the sheet P from one selected paper feed cassette 93 in the paper bank 92 is rotated. The sheet P is separated into one sheet by the separation roller 94 and conveyed to the sheet feeding path 95, and the sheet P is conveyed to the sheet feeding path 97 in the apparatus main body 61 by the conveyance roller 96 and is transferred to the registration roller 98. Stop and stop.
In the case of manual feeding, the sheet P set on the manual feeding tray 99 is fed out by the rotation of the paper feeding roller 100, and is separated into one sheet by the separation roller 101 and conveyed to the manual paper feeding path 102. Then, it hits the registration roller 98 and temporarily stops.
The registration roller 98 starts to rotate at an accurate timing according to the composite color image on the intermediate transfer belt 64, and feeds the sheet P that has been temporarily stopped between the intermediate transfer belt 64 and the secondary transfer device 78. . Then, a color image is transferred onto the sheet P by the secondary transfer device 78.

The sheet P on which the color image has been transferred is conveyed to a fixing device 81 by a secondary transfer device 78 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. . Thereafter, the sheet P is guided to the discharge side by the switching claw 103, is discharged onto the discharge tray 105 by the discharge roller 104, and is stacked there.
When the double-sided copy mode is selected, the sheet P on which an image is formed on one side is conveyed to the sheet reversing device 84 side by the switching claw 103, reversed there and led to the transfer position again, and this time an image is formed on the back side. Thereafter, the paper is discharged onto the paper discharge tray 105 by the discharge roller 104.
In the above-described configuration, the present invention can be applied to the transfer device 65 as a belt conveyance device that conveys the superimposed image and the rotational drive of the photosensitive member 70.

1 is a perspective view of a relative position detection device according to a first embodiment. It is a block diagram which shows a detection process. It is a figure which shows the digitized signal. It is a perspective view of a light shaping means. 1 is a schematic configuration diagram of an image forming apparatus. 2 is a perspective view of a belt conveyance device provided in the image forming apparatus. FIG. It is a perspective view of the head part of the relative position detection apparatus concerning a 2nd embodiment. It is a perspective view of the light shaping means of the relative position detection apparatus which concerns on 3rd Embodiment. It is a figure which shows the relationship between the diameter of a light beam, and the magnitude | size of a slit row | line | column. It is a figure explaining the light quantity distribution of the light beam in the relative position detection apparatus which concerns on 4th Embodiment. It is a perspective view of the head part of the relative position detection apparatus concerning a 5th embodiment. It is a schematic sectional drawing of the relative position detection apparatus which concerns on 6th Embodiment. It is a perspective view of the relative position detection apparatus which concerns on 7th Embodiment. It is a figure which shows the example of application to a belt conveying apparatus. It is a figure which shows the other example of application to a belt conveying apparatus. 1 is a schematic configuration diagram of a color image forming apparatus capable of implementing the present invention. It is a figure which shows the waveform of the positioning error by the speed variation of the belt in the conventional color image forming apparatus.

Explanation of symbols

21 Scale 21a, 21b Mark 22 Head part 26, 27 Light source 28a, 28b Light shaping means 29, 30 Light receiving element 31 as light receiving member 31 Synthetic quartz glass plate as the same member 33 Correction calculating part 44 Gap adjusting member 51 Disc substrate

Claims (13)

A scale on which marks are formed at substantially constant intervals; and a head portion that irradiates the scale with a light beam, receives light reflected or transmitted by the mark, and photoelectrically converts the scale; and the relative relationship between the scale and the head portion In a relative position detection device that detects a change in position,
The head unit includes a light source, a light shaping unit that shapes light from the light source and generates a light beam that irradiates the scale, and a light receiving member that receives the light beam that passes through the mark. And a plurality of light beams at different positions in the relative movement direction of the head unit, the light receiving member photoelectrically converts the plurality of light beams into separate electrical signals, and the light shaping means is on the same member A relative position detecting device formed. The relative position detection device according to claim 1,
A relative position detection device, comprising: a correction calculation unit that generates a relative position signal in which a gap error between the marks is corrected based on a plurality of detection signals from the plurality of light beams. The relative position detection device according to claim 1 or 2,
The relative position detecting device, wherein the light shaping means is formed of a material having a low linear expansion coefficient. In the relative position detection device according to claim 3,
The relative position detecting device, wherein the material having a low linear expansion coefficient is a glass material. In the relative position detection apparatus in any one of Claims 1-4,
2. The relative position detecting device according to claim 1, wherein the light shaping means is a plurality of slit rows. The relative position detection device according to claim 5,
The relative position detection device according to claim 1, wherein the light beam incident on the light shaping means has a larger beam diameter than a light passage region of the slit row. In the relative position detection device according to any one of claims 1 to 6,
The relative position detection device according to claim 1, wherein the light beam incident on the light shaping means has a uniform light amount distribution. In the relative position detection device according to any one of claims 1 to 7,
A relative position detecting device having a gap adjusting member for maintaining a constant gap between the scale and the head portion. The relative position detection device according to claim 8,
The relative position detecting device, wherein the light shaping means is configured integrally with the gap adjusting member.   A belt conveyance device having the relative position detection device according to claim 1.   An image forming apparatus comprising the belt conveyance device according to claim 10. In the relative position detection device according to any one of claims 1 to 9,
2. The relative position detecting device according to claim 1, wherein the scale is formed by radially forming the marks on a disk substrate.   An image forming apparatus having a drive device comprising the relative position detection device according to claim 12.

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