JP2004199044A - Driving controller and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a mark detection error small even if a belt member is displaced in a surface normal direction when a plurality of marks provided to the belt member are optically detected. <P>SOLUTION: A transmission type optical sensor is used to detect marks 85 on a transfer paper conveyor belt 60. The light emitted by a light source 91 is made parallel through a collimator lens 93 and then passes through a mark on the transfer paper conveyor belt to be photodetected by a photodiode 92. Thus, the mark is irradiated with the parallel light, so even if the transfer paper conveyor belt shifts in position in the surface normal direction by the detection timing of respective marks and a detection distance varies, photodetection start timing and photodetection end timing of photodetection of light passing through each mark by the photodiode have nearly no change. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a drive control device for controlling driving of belt members such as a photoreceptor belt and an intermediate transfer belt, and to an image forming apparatus such as a copying machine, a printer, and a facsimile provided with the drive control device.

As this type of drive control device, there is known a drive control device that controls driving of a belt member used for image formation such as a photoreceptor belt, an intermediate transfer belt, and a sheet conveyance belt of an image forming apparatus. When controlling the driving of the belt member for image formation, it is necessary to perform high-precision image alignment with respect to the surface of the belt member or the surface of the recording material conveyed by the belt member. . That is, in the image forming apparatus, the accuracy of the amount of movement of the belt member per unit time and the accuracy of the position (movement position) of a predetermined point on the belt member at a predetermined time greatly affect the quality of an image to be formed. . Therefore, in this type of drive control device, it is required to control the movement amount of the belt member per unit time and the movement position at a predetermined time with high accuracy.
However, the moving speed of the belt member is likely to fluctuate due to various factors such as a load fluctuation received from a member contacting the belt member, and it is extremely difficult to completely eliminate the speed fluctuation of the belt member. Therefore, in this type of drive control device, it has been difficult to control the movement amount of the belt member per unit time and the movement position at a predetermined time with high accuracy.

In various apparatuses, it is often necessary to precisely control the movement and displacement of a moving member included in the apparatus. For example, in a digital color copying machine or the like, traveling of a latent image carrier formed in a drum shape, an intermediate transfer belt used for transferring a toner image, a sheet transport belt for transporting transfer paper, and the like. Must be controlled with high precision, and traveling control by the encoder device is indispensable.
Conventionally, various types of encoder devices have been known, but generally, a main scale is provided on a traveling surface of a moving body, an index scale is arranged close to the main scale, and light from a light source unit is transmitted to the main scale. And the light reflected by the main scale or the light transmitted through the main scale is received by the light receiving means via the index scale, and the intensity of the received light is determined by the main scale and the index scale accompanying the traveling of the moving body. The movement of a moving body is detected by utilizing the fact that it changes with the relative positional displacement of a moving object.
As an example in which traveling control of a moving body using an encoder device is applied to an image forming apparatus, a mark is formed on the surface of a belt that is a moving body, the mark is detected by a sensor, and a belt surface speed is obtained from an obtained pulse interval. There is known a method of calculating and feeding back to control (for example, see Patent Documents 1 and 2).

  Patent Document 1 discloses a drive control device that forms a mark on the front surface or the back surface of an endless belt member and feeds back a result of detection of the mark by a sensor to drive control. More specifically, there is disclosed an apparatus for detecting, with a mark detector, a plurality of marks on a belt member formed so as to be continuous at regular intervals in the surface movement direction of a belt member such as a recording paper transport belt. See FIG. 8 of the literature). According to this device, since the behavior of the belt member itself is directly observed, drive control is performed with higher accuracy than a device that performs drive control based on the rotational angular velocity of the support roller that supports the belt member. It is possible.

  However, it is necessary to use a main scale having a small lattice constant in order to increase the accuracy of the resolution by the above method, and to maintain the contrast, it is necessary to arrange the main scale and the index scale close to each other. .

  In the image forming apparatus, in order to measure the movement amount of the surface of the intermediate transfer belt or the photosensitive drum, when forming a reflection type encoder by forming a main scale on the surface of the belt or the drum, it is necessary to set “the movement of the belt during belt running”. In order to avoid the main scale and index scale coming into contact with each other due to vertical movement due to waving vibration, eccentricity of the drum, etc., it is necessary to provide `` a certain gap '' between both scales. When the “main scale is tilted from the normal state”, there is a problem that the position of the reflected light incident on the light receiving unit changes and a measurement error occurs.

JP-A-9-114348 JP-A-6-263281

  However, it is generally very difficult to uniformly form the thickness of the belt member in the belt moving direction. Further, the thickness of the belt member changes by being deformed by the tension applied during the movement of the belt. Therefore, while the belt member is moving, the interval between the mark provided on the belt member and the mark detector changes. When a mark is detected at a belt portion between a plurality of support members that support the belt member, the interval between the mark and the mark detector fluctuates due to the vibration of the belt portion. As a result of such a change in the interval, the distance between the mark and the mark detector (detection distance) differs for each detection timing. As a result, when the mark detector optically detects the mark, there is a problem that a detection error occurs. Hereinafter, this problem will be specifically described.

FIG. 16 is a schematic configuration diagram of a belt driving device that drives the belt member 560.
This belt driving device includes a belt driving motor 581 and a speed reducer 584 as driving force transmitting means for generating a driving force for driving a driving roller 562 which is a support member for stretching the belt member 560. When the driving force from the belt drive motor 581 is transmitted to the drive roller 562 via the speed reducer 584, the belt member 560 moves in the direction of the arrow in the figure. Further, the belt driving device is provided with a mark sensor 590 as mark detection means for detecting a mark hole 585 provided on the belt member 560. The plurality of marks 585 provided on the belt member 560 include a plurality of through holes that are continuous at a constant interval in the belt moving direction. The mark sensor 590 uses a transmissive photointerrupter in which a light emitting element and a light receiving element are arranged to face each other.

  FIGS. 17A and 17B are enlarged views showing a portion of the belt member 560 facing the mark sensor 590, and FIGS. 17C and 17D are FIGS. 17A and 17B, respectively. 6 is a graph showing an output waveform of the mark sensor 590 corresponding to FIG. When the mark hole 585 moves along with the movement of the belt member 560, the light emitted from the light emitting element 591 of the mark sensor 590 passes only through the mark hole and is intermittently received by the light receiving element 592. Therefore, the output waveform of the mark sensor 590 is as shown in FIGS. Here, conventionally, the light emitted from the light emitting element 591 used in the mark sensor 590 radiates radially around the light emitting element 591. Therefore, for example, when the detection distance L1 between the light emitting element 591 shown in FIG. 17A and the belt surface changes to the detection distance L2 shown in FIG. 17B, the virtual plane C including the light receiving surface of the light receiving element 592 is obtained. The cross-sectional length of the light irradiated upward in the belt moving direction becomes longer. Therefore, the light reception start timing at which the light passing through one mark hole 585 is received by the light receiving element 592 is advanced, and the light reception end timing at which the light is not received by the light receiving element 592 is delayed. Therefore, when the mark interval is small, light reception of the light passing through the next mark hole 585 is started before the light reception of the light receiving element 592 ends. In this case, the output waveform of the mark sensor 590 has a small difference between the low level and the high level as shown in FIG. If the mark interval is sufficiently wide, the difference between the low level and the high level can be increased even if the detection distance changes as described above. However, since high precision is required for drive control of the belt member for image formation, it is important to shorten the sampling interval for mark detection as much as possible. Therefore, it is necessary to narrow the mark interval. The output waveform becomes as shown in FIG. With such an output waveform, for example, when the output is pulsed at a fixed threshold and used, the duty ratio of the pulse fluctuates. In this case, if the mark is detected at the time of rising or falling of the pulse, an error occurs in the mark detection timing.

  When examining a specific error, the mark hole 585 is formed at 1 mm L / S (line and space) in the belt moving direction, the distance between the light emitting element 591 and the mark hole 585, and the distance between the light receiving element 592 and the mark hole 585. An example in which the interval is also 1 mm is given as an example (detection distance L1 = 1 mm shown in FIG. 17A). When the end of the mark hole 585 in the belt moving direction is on a virtual straight line connecting the center of the light emitting element 591 and the center of the light receiving element 592, the divergence angle of light passing through the mark hole 585 is 45 °. Therefore, the sectional length of light in the belt moving direction on the virtual plane C shown in FIG. 17A is 2 mm. In this state, when the mark hole 585 moves toward the light emitting element 591 by 0.5 mm (detection distance L2 = 0.5 mm shown in FIG. 17B), the divergence angle becomes 60 °. As a result, the cross-sectional length of light in the belt movement direction on the virtual plane C shown in FIG. 17B is 4 mm. Therefore, an error of 1 mm already occurs when the end of the mark hole 585 in the belt moving direction is on a virtual straight line connecting the center of the light emitting element 591 and the center of the light receiving element 592. In the 600 dpi image forming apparatus, the line interval of the image corresponding to the belt moving direction is 42 μm. In order to increase the positional accuracy of the lines of each image, the mark detection interval must be shortened in accordance with such a short line interval, so that the above-mentioned error of 1 mm is extremely large. In addition, in the configuration shown in FIG. 16, the above-described fluctuation of the detection distance of 0.5 mm can sufficiently occur. Further, even if the fluctuation of the detection distance is regulated by a known jig for stabilizing the running of the belt, the fluctuation of about 0.1 mm cannot be avoided.

  In the above description, the case where the mark sensor is of the transmission type is taken as an example, so that the vibration of the belt member greatly affects the detection error, and the fluctuation in the thickness of the belt member does not significantly affect the detection error. However, the above-described problem of the occurrence of the detection error can also occur when the mark sensor is a reflection-type mark sensor. In this case, in addition to the vibration of the belt member, the fluctuation in the thickness of the belt member is also detected. It greatly affects the error. In addition, the problem that a detection error occurs occurs even if the driven object is not a belt member for image formation, and it is necessary to control a moving amount per unit time and a moving position at a predetermined time with high accuracy. As for the belt member for image formation, it is an important problem as in the case of the belt member for image formation.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce a detection error caused by a change in a detection distance when optically detecting a plurality of marks provided on a belt member. It is an object of the present invention to provide a drive control device and an image forming apparatus capable of performing the above.
In view of the above-described circumstances, it is an object of the present invention to provide a highly accurate and stable encoder function even when a vertical movement or an inclination occurs on a scale.

In order to achieve the above object, the invention according to claim 1 is directed to a method in which light is applied to a plurality of marks provided on a belt member so as to be continuous at predetermined intervals in a moving direction of the belt member stretched over the plurality of support members. A light irradiating means for irradiating the belt, a light receiving means for receiving a transmitted light or a reflected light of the light irradiated from the light irradiating means toward the mark, and the belt based on an output signal output from the light receiving means. In a drive control device provided with speed / position control means for performing speed control or position control of a member, light emitted from the light irradiation means is substantially parallel light.
According to a second aspect of the present invention, in the drive control device according to the first aspect, the light irradiating means irradiates light having a sectional length in a moving direction of the belt member shorter than an interval between the plurality of marks. It is assumed that.
According to a third aspect of the present invention, in the drive control device according to the first or second aspect, the light irradiating unit irradiates light having a long cross-sectional shape in a direction orthogonal to a moving direction of the belt member. It is characterized by the following.
According to a fourth aspect of the present invention, in the drive control device according to the first, second or third aspect, the light irradiating means irradiates the plurality of marks with a plurality of lights along a moving direction of the belt member. The irradiation interval of the plurality of lights is an integral multiple of a mark interval of a plurality of marks provided on the belt member so as to be continuous at a constant interval.
According to a fifth aspect of the present invention, in the drive control device of the first, second, third or fourth aspect, the light irradiating means irradiates light from a direction orthogonal to a moving direction of the belt member. It is assumed that.
According to a sixth aspect of the present invention, in the drive control device of the fifth aspect, the light irradiating means irradiates light from a normal direction of a surface of the belt member.
According to a seventh aspect of the present invention, there is provided a belt member provided with a plurality of marks continuous at predetermined intervals in the moving direction, and a driving force transmission for transmitting a driving force for moving the belt member to the belt member. And a drive control means for controlling the drive of the drive force transmitting means, wherein the drive control means of claim 1, 2, 3, 4, 5, or 6 is used as the drive control means. It is characterized by having been.

In the drive control device according to the first to sixth aspects and the image forming apparatus according to the seventh aspect, a plurality of marks provided on the belt member are optically detected so as to be continuous at predetermined intervals in the belt moving direction, and the detection result is provided. , The speed control or the position control of the belt member is performed. For this mark detection, a light irradiating unit that irradiates a plurality of marks with light and a light receiving unit that receives transmitted light or reflected light of the irradiated light are used.
The mark provided on the belt member may be a mark that allows light to pass therethrough, such as a through-hole, or a mark that reflects light, such as a reflector. The configuration and arrangement of the means and the light receiving means are appropriately determined. Further, the interval between the marks provided on the belt member is not limited to the one in which all of the marks are constant, and the interval between the marks which are not constant may be periodically repeated. Is determined as appropriate. The speed / position control means may use the output signal of the light receiving means as it is, or may use the output signal converted to another signal or information.
In the present drive control device and the present image forming apparatus, the light emitted from the light irradiation means is substantially parallel light. Since the substantially parallel light has high directivity, the cross section of the light at the moment when the light is irradiated from the light irradiation means is almost the same as the cross section when the light reaches the mark or the cross section when the light reaches the light receiving means. . That is, the light irradiated from the light irradiation means does not diverge radially. Therefore, even if the distance between the light irradiating means and the mark or the distance between the light receiving means and the mark changes at each mark detection timing, the light receiving start timing and the light receiving end timing of the light passing or reflected by one mark by the light receiving means. There is almost no change. Therefore, it is possible to suppress a detection error caused by a change in the detection distance.

The encoder device according to the present invention is configured such that "a scale having a portion having a predetermined reflectance or transmittance arranged in a one-dimensional grid pattern has an aperture having an opening width substantially equal to the grid width in the scale. Irradiation through the slit, the light intensity of the light reflected by the scale or the light transmitted through the scale is detected by the light receiving means, and the change in the light intensity detected by the light receiving means causes the displacement of the scale relative to the slit. Encoder device for detecting the
The grid width in the scale is the width of the “portion having a predetermined reflectance or transmittance” in the grid array direction.
Various light sensors can be used as the “light receiving unit”.

The encoder device according to claim 8 is characterized by the following points (claim 8).
That is, the encoder device according to claim 8 includes the gap regulating member and the pressing unit.
The “gap regulating member” is a member for keeping the gap between the slit and the scale constant.
"Pressing means" is means for elastically pressing the slit against the scale via the gap regulating member. Therefore, the gap regulating member pressed by the slit presses against the scale to keep the gap between the slit and the scale constant.
Therefore, when the scale is formed on the peripheral surface of the belt or drum, `` Even if the scale fluctuates or tilts in the direction perpendicular to the peripheral surface due to vertical movement during belt running or eccentricity of the drum, The gap between the scale and the slit does not change.

The encoder device according to claim 8 may be configured such that “the light source unit and the light receiving unit are housed in the sensor housing, and the pressing unit is disposed between the sensor housing and the slit”. ).
The encoder device according to claim 8, wherein the light source unit and the light receiving unit are housed in the sensor housing, the pressing unit presses the sensor housing toward the scale, and the slit and the gap regulating member are disposed in the sensor housing. Configuration "(claim 10).
The encoder device according to claim 8, "the sensor housing in which the light source unit and the light receiving unit are housed is held so as to be displaceable around a position where light passing through the slit is irradiated on the scale. Configuration "(claim 11).
The encoder device according to any one of claims 8 to 11 may be configured such that “the light from the light source unit is irradiated on the scale so as to be orthogonal to the moving direction of the scale” (claim 12). ).

The light source unit of the encoder device according to any one of claims 8 to 12 can have “a collimating lens that collimates light emitted from the light source” (claim 13), but is replaced with a collimating lens. It can also have a “light-collecting lens”.
The slit of the encoder device according to any one of claims 8 to 13 can be "configured as a member having an opening and having a spring property, and also serves as a gap regulating member and a pressing means." ).
In the encoder device according to the fourteenth aspect, the “spring member” serving as the “slit serving as both the gap regulating member and the pressing means” may be a leaf spring (claim 15) or a resin film (claim). Item 16) can also be used. When a member having spring properties is used as a resin film, "a structure in which a metal film is provided on a transparent film surface and an opening is formed in the metal film so as to have a slit function" can be used. (Claim 17). Alternatively, the resin film may be configured to have "a structure having an opening pattern formed by an absorbing portion and a transmitting portion with respect to the wavelength of light emitted from the light source portion" (claim 18).
The encoder device according to any one of claims 8 to 17 preferably has "lubricating means for lubricating between the scale and the gap regulating member" (claim 19).
The "lubricating means" may be configured as a lubricant applying means for applying a lubricant between the gap regulating member and the scale (claim 20), and the gap regulating member itself may have lubricity. May be.

The "gap regulating member" in the encoder device according to any one of claims 8 to 20 can be "constituted by a roller or a ball member and rolled on the scale" (claim 21).
The slit in the encoder device according to any one of claims 8 to 21 can be “having a plurality of apertures in a direction in which the one-dimensional grid on the scale is arranged in the grid” (claim 22).
The encoder device according to any one of claims 8 to 22 can include a “cleaning member that cleans the scale” (claim 23).
The moving device according to the present invention is a “moving device that travels around a peripheral surface of a moving body formed in a belt shape or a drum shape”, and includes the encoder device according to any one of claims 8 to 23, The scale of the encoder device is formed on a moving body (claim 24).
An image forming apparatus according to the present invention is an image forming apparatus having the moving device according to claim 24 (claim 25). The moving device is configured as a moving device that moves a latent image carrier formed in a belt shape or a drum shape or a toner image transfer unit (such as an intermediate transfer belt) as a moving body.

In the invention according to claim 26, a scale in which a reflecting portion and a non-reflecting portion or a transmitting portion and a non-transmitting portion are alternately arranged one-dimensionally with substantially the same width, a mechanism for moving the scale in the arrangement direction, and the scale A light emitting means for irradiating a light beam on the scale, and a light receiving means for detecting reflected light or transmitted light from the scale, and an encoder device for detecting a displacement of the scale in the arrangement direction by an output of the light receiving means. ,
The pitch of the scale is P1, the size of the luminous flux from the light emitting means on the reference plane, which is a design position of the scale, in the arrangement direction is LR, and the scale generated during the movement of the scale is LR. When the maximum displacement amount in the direction perpendicular to the scale surface is dzM, the irradiation angle of the center light of the light beam with respect to the normal line of the reference surface is θb, the divergence angle of the light beam is θa, and k is a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
K-1 <LR'm / P1≤LR / P1≤LR'M / P1 <k
Is satisfied.

The invention according to claim 27 is characterized in that, in the encoder device according to claim 26, LR / P1 = k-0.5.
In the invention according to claim 28, a scale in which a reflecting portion and a non-reflecting portion or a transmitting portion and a non-transmitting portion are alternately arranged one-dimensionally with substantially the same width, a mechanism for moving the scale in the arrangement direction, and the scale Light emitting means for irradiating a plurality of beams at equal intervals, and light receiving means for detecting reflected light or transmitted light from the scale, and the displacement of the scale in the arrangement direction is provided by the output of the light receiving means. In the detecting encoder device,
The pitch of the scale is P1, the pitch in the arrangement direction formed by the plurality of beams on the reference plane, which is the design position of the scale, is P2, and the pitch is perpendicular to the scale plane generated while the scale is moving. When the maximum displacement amount from the reference plane in any direction is dzM, the irradiation angle of the center light of the beam with respect to the normal line of the reference plane is θb, the divergence angle of the beam is θa, and j is a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
And P2′m is the minimum pitch of the beam, P2′M is the maximum pitch of the beam, and the moire pitch between the scale pitch and
Pmm = P1 × P2′m / (P1−P2′m)
PmM = P1 × P2′M / (P2′M−P1)
And put
j-1 <LR'm / (Pmm / 2) <j
And,
j-1 <LR'M / (PmM / 2) <j
Is satisfied.
According to a twenty-ninth aspect of the present invention, in the encoder device according to the twenty-eighth aspect, n is the number of beams, and P2 ′ is a beam pitch in a variation range.
(2n-2) / (2n-1) <P2 '/ P1 <2n / (2n-1)
Is satisfied.

The invention according to claim 30 is characterized in that, in the encoder device according to claim 28 or 29, P2 = P1.
In the invention according to claim 31, a scale in which transmissive portions and non-transmissive portions are alternately arranged in a one-dimensional manner with substantially equal widths, a mechanism for moving the scale in the arrangement direction, and a light projecting means for irradiating the scale with a light beam A mask having a plurality of slit-shaped transmitting portions provided between the light projecting means and the scale; and a light receiving means for detecting transmitted light from the scale, and the scale is provided by an output of the light receiving means. In the encoder device that detects the displacement in the array direction of
The pitch of the scale is P1, the pitch in the arrangement direction formed by a plurality of beams transmitted through the plurality of slits on a reference plane, which is a design position of the scale, is P3, and the scale is generated during movement. The maximum displacement from the reference plane in a direction perpendicular to the scale surface is dzM, the irradiation angle of the center light of the light beam with respect to the normal line of the reference surface is θb, the divergence angle of the beam is θa, and j is As a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
And P3′m is the minimum pitch of the beam, P3′M is the maximum pitch of the beam, and the moire pitch generated between the scale pitch and
Pmm = P1 × P3′m / (P1-P3′m)
PmM = P1 × P3′M / (P3′M−P1)
And put
j-1 <LR'm / (Pmm / 2) <j
And,
j-1 <LR'M / (PmM / 2) <j
Is satisfied.

In the invention according to claim 32, in the encoder device according to claim 29, p is the number of slits, and P3 ′ is a beam pitch in a variation range.
(2p-2) / (2p-1) <P3 '/ P1 <2p / (2p-1)
Is satisfied.
A thirty-third aspect of the present invention is the encoder device according to the thirty-first or thirty-second aspect, wherein P3 = P1.
According to a thirty-fourth aspect, in the encoder device according to any one of the twenty-sixth to thirty-fourth aspects, dzM = 0 is always set.
According to a thirty-fifth aspect of the present invention, in the encoder device according to any one of the twenty-sixth to thirty-fourth aspects, θa = 0 is configured.
According to a thirty-sixth aspect, in the encoder device according to any one of the twenty-sixth to thirty-fifth aspects, the encoder device is configured so that θb = 0.
According to a thirty-seventh aspect of the present invention, in the moving device having the encoder device according to any one of the twenty-sixth to thirty-fourth configurations, the moving device travels on a peripheral surface of a moving body formed in a belt shape or a drum shape. Is characterized in that the scale is formed on the peripheral surface of the moving body.
According to a thirty-eighth aspect of the present invention, there is provided an image forming apparatus including the moving device according to the thirty-seventh aspect.

According to the present invention, there is an excellent effect that, when a plurality of marks provided on a belt member are optically detected, it is possible to reduce a detection error caused by a change in the detection distance.
Further, according to the present invention, a novel encoder device / moving device and image forming device can be realized.
As described above, since the gap between the slit and the scale is kept at the predetermined gap by the gap regulating member, the encoder device of the present invention can read the scale stably and accurately, and can improve the running state of the moving body. Can be detected. Therefore, a moving device using such an encoder device can satisfactorily control the traveling state of the moving body based on the output of the encoder device, and can use these moving devices as a photosensitive member moving device or an intermediate transfer belt moving device in an image forming apparatus. By using as such, good image formation can be realized.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter, referred to as a “laser printer”) that is an image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram of the laser printer according to the present embodiment. This laser printer is provided with four sets of image forming means 1M, 1C, 1Y, 1K (hereinafter, each of them) for forming an image of each color of magenta (M), cyan (C), yellow (Y), and black (K). The suffixes M, C, Y, and K of the reference numerals indicate members for magenta, cyan, yellow, and black, respectively.) They are arranged in order from the upstream side in the direction of arrow A). Each of the image forming means 1M, 1C, 1Y, and 1K includes a photosensitive unit having photosensitive drums 11M, 11C, 11Y, and 11K as a latent image carrier, and a developing unit. The image forming means 1M, 1C, 1Y, and 1K are arranged such that the rotation axes of the photosensitive drums in the respective photosensitive units are parallel and are arranged at a predetermined pitch in the transfer paper moving direction. Is set.

  The laser printer is provided with an optical writing unit 2 and paper feed cassettes 3 and 4 in addition to the image forming means 1M, 1C, 1Y and 1K. Further, a transfer unit 6 having a transfer paper transport belt 60 as a belt member for transporting the transfer paper toward the transfer unit facing each photosensitive drum 11 is also provided. Also provided are a registration roller 5 composed of a pair of rollers for supplying transfer paper to the transfer paper transport belt 60, a belt-fixing type fixing unit 7, a paper discharge tray 8, and the like. The laser printer also includes a not-shown manual feed tray, toner supply container, waste toner bottle, double-sided / reversed unit, power supply unit, and the like.

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 of each of the photosensitive drums 11M, 11C, 11Y, and 11K with a laser beam while scanning based on image data. I do.
A dashed line in FIG. 2 indicates a transfer path of the transfer paper. The transfer paper fed from the paper feed cassettes 3 and 4 is transported by transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration roller 5 is provided. The transfer paper is supplied to the transfer paper transport belt 60 by the registration roller 5 at a predetermined timing, and is transported so as to pass through each transfer section facing each photosensitive drum 11. As a result, the toner images formed on the photosensitive drums 11 formed by the image forming means 1M, 1C, 1Y, and 1K are sequentially superimposed on the transfer paper and transferred, and a color image is formed on the transfer paper. The transfer paper on which the color image is formed is discharged onto a discharge tray 8 after the toner image is fixed by the fixing unit 7.

FIG. 3 is an enlarged view showing a schematic configuration of the yellow image forming means 1Y among the image forming means 1M, 1C, 1Y, and 1K. The other image forming means 1M, 1C, and 1K have the same configuration, respectively, and a description thereof will be omitted.
In FIG. 3, the image forming unit 1Y includes the photoconductor unit 10Y and the developing unit 20Y as described above. The photoreceptor unit 10Y includes a photoreceptor drum 11Y, a cleaning blade 13Y as a photoreceptor cleaning unit for cleaning the photoreceptor drum surface, a charging roller 15Y for uniformly charging the photoreceptor drum surface, and the like. In addition, a lubricant application / discharge brush roller 12 </ b> Y having a function of applying a lubricant to the surface of the photosensitive drum and removing charge from the surface of the photosensitive drum is also provided. The brush portion of the lubricant applying and removing brush roller 12Y has a brush portion made of conductive fiber, and an unillustrated removing power source for applying a removing bias is connected to the core portion.

  In the photoconductor unit 10Y having the above configuration, the surface of the photoconductor drum 11Y is uniformly charged by the charging roller 15Y to which a voltage is applied. When the laser beam modulated and deflected by the optical writing unit 2 is irradiated on the surface of the photosensitive drum 11Y while being scanned, an electrostatic latent image is formed on the surface of the photosensitive drum 11Y. The electrostatic latent image on the photosensitive drum 11Y is developed by a later-described developing unit 20Y to become a yellow toner image. At the transfer section Pt where the transfer paper 100 on the transfer paper transport belt 60 passes, the toner image on the photosensitive drum 11Y is transferred to the transfer paper 100. The surface of the photoreceptor drum 11Y after the transfer of the toner image is applied with a predetermined amount of lubricant by a lubricant application / discharge brush roller 12Y and is discharged, and then is cleaned by a cleaning blade 13Y. It is provided for the formation of an electrostatic latent image.

  The developing unit 20Y uses a two-component developer containing a magnetic carrier and a negatively charged toner as a developer for developing the electrostatic latent image. The developing unit 20Y includes a developing roller 22Y as a developer carrier, which is disposed so as to be partially exposed from an opening on the photosensitive drum side of the developing case 21Y, conveying screws 23Y and 24Y, a developing doctor 25Y, A toner density sensor (T sensor) 26Y, a powder pump 27Y and the like are provided.

  In FIG. 3, the developer contained in the developing case 21Y is frictionally charged by being agitated and transported by the transport screws 23Y and 24Y. Then, a part of the developer is carried on the surface of the developing roller 22Y, and after the layer thickness is regulated by the developing doctor 25Y, the developer is conveyed to a developing position facing the photosensitive drum 11Y. At the developing position, the electrostatic latent image on the photosensitive drum 11Y is developed by the charged toner in the developer on the developing roller 22Y. The toner concentration of the developer in the developing case 21Y is detected by the toner concentration sensor 26Y, and toner is supplied by the powder pump 27Y as needed.

  FIG. 4 is a schematic configuration diagram of the transfer unit 6. As a material of the transfer paper transport belt 60 of the transfer unit 6, for example, PVDF (polyvinylidene fluoride) can be used. The transfer paper transport belt 60 is rotatably stretched by four support rollers 61, 62, 63, and 64 as grounded support members. The exit roller 62 on the downstream side in the transfer paper moving direction is a drive roller for frictionally driving the transfer paper transport belt 60, and is connected to a belt drive motor (not shown). When the transfer paper transport belt 60 is rotated in the direction of the arrow by the exit roller 62, the transfer paper 100 is carried and transported toward each of the transfer sections facing the photosensitive drums 11M, 11C, 11Y, and 11K of each image forming means. Is done.

  Further, transfer bias applying members 67M, 67C, 67Y, 67K are provided as transfer electric field forming means for forming a transfer electric field in each transfer section. These transfer bias applying members 67M, 67C, 67Y, 67K transfer the toner images of the respective colors by opposing the respective photosensitive drums 11M, 11C, 11Y, 11K so as to contact the back surface of the transfer paper transport belt 60. Transfer nip is formed. The transfer bias applying members 67M, 67C, 67Y, and 67K used in the present embodiment are composed of Mylar fixed brushes. Are configured such that a positive voltage having a reverse polarity is applied. By the transfer bias applied via the transfer bias applying members 67M, 67C, 67Y, 67K, transfer charges are applied to the transfer paper transport belt 60, and the surfaces of the photosensitive drums 11M, 11C, 11Y, 11K in each transfer section. A transfer electric field having a predetermined strength is formed between the transfer paper and the transfer paper transport belt 60.

  Further, the transfer unit 6 is provided with backup rollers 68M, 68C, 68Y, 68K for pressing the transfer paper transport belt 60 against the respective photosensitive drums 11M, 11C, 11Y, 11K. The transfer paper transport belt 60 is wound around a part of the peripheral surface of the photosensitive drum 11Y on the upstream side in the moving direction. Thereby, the contact pressure between the transfer paper 100 and each photosensitive drum in the transfer nip is increased, and the transfer efficiency of each toner image in each transfer unit is increased.

An electrostatic attraction roller 65 is provided at a portion of the transfer unit 6 facing the support roller 61 so as to be in contact with and facing the transfer paper transport belt 60 as a transfer material attraction electrode member. The electrostatic attraction roller 65 is formed by forming a conductive foamed elastic body layer on a cored bar. As a material of the elastic layer, for example, chloroprene rubber having a specific resistivity of 10 ⁵ Ωcm can be used. A voltage is selectively applied to the electrostatic attraction roller 65 from a power supply 65a for attracting transfer paper and a power supply 65b for reverse polarity as a bias applying means. The transfer paper suction power supply 65a is a power supply of a constant current control system, and applies a charge of positive polarity opposite to the normal polarity of the toner to the transfer paper. In the present embodiment, the current flowing through the support roller 61 is controlled to be, for example, plus 15 μA. The transfer paper that has passed between the electrostatic attraction 65 and the support roller 61 in a state where power is supplied from the transfer paper attraction power supply 65 a is electrostatically attracted onto the transfer paper transport belt 60. The power supply 65b for the reverse polarity is a power supply of a constant voltage control system, and increases the charge of the negatively charged toner having the normal polarity on the transfer paper transport belt 60 or increases the charge of the positively charged reverse. For inverting the polarity toner to the negative polarity or transferring the negatively charged toner adhering to the surface of the electrostatic attraction roller 65 to the surface of the transfer paper transport belt 60 to clean the electrostatic attraction roller 65. It is. In the present embodiment, for example, a constant voltage of −2 kV is applied to the suction roller 65. The switching of the voltage applied to the electrostatic attraction roller 65 is performed by a main body control unit (not shown).

  In the transfer unit 6, a portion of the transfer paper transport belt 60, which is stretched by the two support rollers 63 and 64, is of a bias cleaning type that removes toner adhered to the surface of the transfer paper transport belt 60. A bias cleaner 70 as cleaning means is provided. The bias cleaner 70 has a conductive cleaning roller 71 disposed opposite to the surface of the transfer paper transport belt 60, and applies a negatively charged toner to the cleaning roller 71 side between the cleaning roller 71 and the transfer paper transport belt 60. A cleaning bias power supply 75 is provided as a cleaning bias applying unit for applying a bias for moving the cleaning roller 71 to form a cleaning electric field. Further, a removing blade 72 for removing the toner adhered to the cleaning roller 71 from the roller surface is also provided. The removal blade 72 is disposed so as to contact the surface of the cleaning roller 71 with a contact width slightly larger than the image area width of the cleaning roller 71 in the axial direction. An opposing roller 73 urged by a spring 74 is provided at a position opposing the cleaning roller 71 via the transfer paper transport belt 60.

Next, the position control of the transfer paper transport belt 60, which is a feature of the present invention, will be described.
FIG. 5 is a schematic configuration diagram of a belt driving device 80 as a driving device for driving the transfer paper transport belt 60 in the present embodiment. The belt driving device 80 includes a belt driving motor 81 as a driving force transmission unit that generates a driving force for driving the driving roller 62, and a position control device 82 as a movement position recognition unit and a position control unit. Among them, the position control device 82 and a mark sensor 90 described later constitute a drive control device as drive control means.
In the present embodiment, a stepping motor is used as the belt drive motor 81. The driving force from the belt driving motor 81 is transmitted to the driving roller 62 via a speed reducer 84 provided coaxially outside the driving roller 62 in the axial direction. As a result, the drive roller 62 is driven to rotate, and the transfer paper transport belt 60 moves in the direction of arrow A in the figure due to friction.

  A plurality of marks 85 composed of through holes are provided on the side of the transfer paper transport belt 60 in the moving direction so as to be continuous at a constant interval in the moving direction. A mark sensor 90 is provided as mark detection means so as to face a region through which the plurality of marks 85 pass as the transfer paper transport belt 60 moves. The mark sensor 90 outputs a mark detection signal which is an output signal when a mark is detected, and the mark detection signal is sent to a position control device 82 as speed / position control means.

  FIG. 1 is a schematic configuration diagram of the mark sensor 90. In the present embodiment, a transmission type optical sensor is used as the mark sensor 90 for detecting the mark 85 on the transfer paper transport belt 60. The mark sensor 90 of the present embodiment includes a light source 91 composed of an LED (light emitting diode) and a photodiode 92 as light receiving means. After the light from the light source 91 is collimated by the collimator lens 93, the light is applied to a region of the transfer paper transport belt 60 where the mark 85 passes. The light irradiation means includes a light source 91 and a collimating lens 93. When the irradiated parallel light passes through the mark 85, the passed parallel light is received by the photodiode 92. When the parallel light is received by the photodiode 92, an output signal as shown in FIG. 6A is output from the photodiode 92. This output signal is pulsed by the threshold value shown in FIG. 6A as shown in FIG. 6B, and this pulse signal is output from the mark sensor 90 as a mark detection signal. The mark detection means is not limited to the transmission type optical sensor used in the present embodiment as long as it can detect the mark 85 provided on the transfer paper transport belt 60. For example, when the marks 85 on the transfer paper transport belt 60 are formed in a reflective pattern, a reflective optical sensor can be used. When the mark 85 is formed by a reflection pattern, a scale for an encoder can be used. Commercially available film scales for linear encoders have high resolution, are mass-produced, and are available at low prices, so that marks at regular intervals can be formed on the transfer paper transport belt 60 at low cost.

  In the present embodiment, the light passing through the collimator lens 93 has a cross-sectional length in the moving direction of the transfer paper transport belt 60 shorter than the interval between the marks 85. As a result, the irradiated light passes through one mark, is completely blocked by the transfer paper transport belt 60, and then passes through the next mark. Therefore, in the photodiode 92, there is a period in which no light is received between the marks. Thereby, the minimum value can be obtained as the low level value (lower limit peak value) in the output signal output from the photodiode. Therefore, the difference between the high level value and the low level value can be maximized, so that stable mark detection can be performed.

  Further, in the present embodiment, as shown in FIG. 1, the light that has passed through the collimator lens 93 is irradiated from a direction perpendicular to the moving direction of the transfer paper transport belt 60. If the optical path is inclined from the direction perpendicular to the moving direction of the transfer paper conveying belt 60 to the moving direction of the transfer paper conveying belt 60 as shown in FIG. , The light receiving start timing by the photodiode 92 is delayed, and the light receiving end timing is also delayed. As a result, accurate mark detection may not be performed. On the other hand, in the present embodiment, as shown in FIG. 7B, since the optical path is orthogonal to the moving direction of the transfer paper transport belt 60, the transfer paper transport belt 60 is moved from the position indicated by the dotted line in the figure. Even when displaced to the position indicated by the solid line in the figure, there is no change in the light reception start timing and the light reception end timing by the photodiode 92.

  In the method of forming marks on the transfer paper transport belt 60, a resin tape 86 as a flexible member on which a plurality of marks 85 continuous at a constant interval is formed is bonded to one side of the transfer paper transport belt 60 in the moving direction. Adopt a method to do. In addition to this method, there is a method in which the marks 85 are formed at the same time as the transfer paper transport belt 60 is formed. However, this method cannot make the mark interval constant when the contraction rate of the entire belt is uneven. However, according to the bonding method employed in the present embodiment, even if the contraction rate of the transfer paper transport belt 60 is not uniform, this does not affect the mark interval, and the mark interval can be made constant.

FIG. 8 is a functional block diagram illustrating a schematic configuration of the position control device 82 according to the present embodiment.
The position control device 82 is provided with a microcomputer 82a that performs overall control. The microcomputer 82a has a configuration in which a microprocessor (CPU) as an arithmetic unit, a read-only memory (ROM), and a random access memory (RAM) are connected via a bus. Further, the position control device 82 includes a state detection interface (I / F) 82b for receiving a mark detection signal from the mark sensor 90. The output of the state detection I / F 82b is input to the microcomputer 82a via the bus. The state detection I / F 82b includes a counter (not shown) that counts the number of pulses of the mark detection signal from the mark sensor 90, and converts the mark detection signal into a digital value. Further, the position control device 82 is provided with an interpolation clock counter 82c, and outputs the counted clock number to the microcomputer 82a via the bus.
In the present embodiment, a case has been described in which the position control of the belt moving device 80 is executed by the microcomputer 82a. However, instead of the microcomputer 82a, a DSP (digital signal processor) having a high numerical processing capability or the like may be used. it can.

  Further, the position control device 82 includes a drive I / F 82d and a driver 82e connected to the belt drive motor 81. The driving I / F 82d is connected to a microcomputer 82a via a bus. The driving I / F 82d converts a digital signal indicating a calculation result in the microcomputer 82a into an analog signal and supplies the analog signal to the driver 82e. Thus, the current and voltage applied to the belt drive motor 81 are controlled by the driver 82e. As a result, the microcomputer 82a drives the transfer paper transport belt 60 so that the rotational position of the transfer paper transport belt 60 always follows a predetermined target position by repeating the arithmetic processing described later based on the mark detection signal. be able to.

FIG. 9 is a control block diagram showing the control performed by the position control device 82 to grasp the actual rotation position of the transfer paper transport belt 60.
The position control device 82 counts the number of pulses of the mark detection signal from the mark sensor 90 by a mark counter provided in the state detection I / F 82b. The position control device 82 generates a continuous interpolation clock signal by a clock generation circuit provided as an interpolation clock generation means provided in the interpolation clock counter 82c. The number of clocks of the interpolation clock signal is counted by a clock counter provided in the interpolation clock counter 82c. The clock counter is reset at a rising edge generated when the mark counter counts. That is, the clock counter is reset every time a mark is detected.

  The microcomputer 82a samples the mark count value obtained by the mark counter and the clock count value obtained by the clock counter at a predetermined sampling interval. Then, the microcomputer 82a performs an operation of multiplying the mark count value by the mark interval on the transfer paper transport belt 60. In the present embodiment, the mark interval is 169 μm. Further, the microcomputer 82a performs an operation of multiplying the clock count value by a clock equivalent interval. The clock equivalent interval indicates a moving distance of the transfer paper transport belt 60 corresponding to the clock time. In this embodiment, since the moving speed of the transfer paper transport belt 60 is 200 mm / s and the interpolation clock signal is 576 kHz, the clock equivalent interval is about 0.347 μm obtained from the following equation (1).

Number 1
200 [mm / s] × (1/576 [kHz]) = 3.4722 × 10 ⁻⁷ [m]

  The microcomputer 82a calculates the sum of the two results calculated as described above. That is, the mark counter counts each time the transfer paper transport belt 60 moves 169 μm. The clock counter counts every time the transfer paper transport belt 60 moves by 0.347 μm while the transfer paper transport belt 60 moves by 169 μm. Therefore, the sum of these indicates the actual detailed rotational position of the transfer paper transport belt 60. Therefore, the microcomputer 82a can accurately grasp the actual detailed rotation position (movement position) of the transfer paper transport belt 60 at each sampling.

  The microcomputer 82a, which has grasped the actual rotation position of the transfer paper transport belt 60 in this manner, compares the actual rotation position with the target rotation position at the time of sampling (hereinafter, referred to as "target position"). I do. Specifically, a difference between the actual rotation position and the target position is calculated, and the calculation result is output to the driving I / F 82d. As a result, the driving I / F 82d outputs a current or voltage whose difference becomes zero to the belt driving motor 81 via the driver 82e. As a result, position control is performed so that the rotational position of the transfer paper transport belt 60 always becomes the target position.

[Modification 1]
Next, a modified example of the mark sensor in the above embodiment (hereinafter, this modified example will be referred to as “modified example 1”) will be described.
The transfer paper transport belt 60 may meander due to a deviation in the degree of parallelism between the axes of the support rollers 61, 62, 63, 64 stretching the belt. When the meandering occurs, the position in the width direction of the transfer paper transport belt 60 is shifted. As a result, the moving path of the mark 85 that moves along with the transfer paper transport belt 60 may deviate from the optical path of the mark sensor, and accurate mark detection may not be performed. For example, when the cross section of the light used by the mark sensor is round and the shape of the mark 85 is the same size as the cross section of the light, the position of the transfer paper transport belt 60 in the width direction is the mark 1. The mark detection cannot be performed only by the displacement. In view of this, the first modification employs a configuration capable of performing stable mark detection even while the transfer paper transport belt 60 is meandering.

  FIG. 10 is an explanatory diagram illustrating a state in which light from the light source 191 is applied to the mark 85 of the transfer paper transport belt 60 in the first modification. As shown, the mark 85 of the transfer paper transport belt 60 has an elongated shape in a direction perpendicular to the belt moving direction. Further, the light source 191 of the mark sensor according to the first modification emits light having a long cross-sectional shape in a direction (Y direction in the drawing) orthogonal to the moving direction (X direction in the drawing) of the transfer paper transport belt 60. Irradiate. This light is collimated by the collimator lens 193 and then applied to the area where the mark 85 on the transfer paper transport belt 60 passes, as in the above embodiment. By irradiating the mark 85 with such light, a portion where the region L0 irradiated with the light and the moving path of the mark 85 overlap is widened. Even when the transfer paper conveyance belt 60 meanders and its width direction position is shifted, mark detection can be performed as long as there is an overlapping portion. In the first modification, the mark in the belt width direction is set so that the area L0 to which light is irradiated and the movement path of the mark 85 always overlap within a range in which the position of the transfer paper conveyance belt 60 in the width direction can move at the time of meandering. The length and the section length of the light are set. Therefore, according to the first modification, stable mark detection can be performed even while the transfer paper transport belt 60 is meandering.

[Modification 2]
Next, another modified example of the mark sensor in the above embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
The transfer paper transport belt 60 provided with the mark 85 is disposed inside the laser printer, and the toner scattered inside the apparatus adheres thereto. If the scattered toner adheres to the area where the mark 85 is provided, the amount of light passing through the mark may decrease or may not pass. In this case, mark detection is unstable or mark detection is not possible. Normally, even if the scattered toner adheres, the toner is cleaned by the bias cleaner 70.However, there are cases where the toner is still fixed or the shape of the mark 85 is deformed by the bias cleaner 70. Stable mark detection may be difficult. In view of this, the second modification employs a configuration in which even when some of the marks 85 are difficult to detect due to contamination by scattered toner or the like, stable mark detection can be performed.

  FIG. 11 is an explanatory diagram illustrating a state in which light from the light source 291 is applied to the mark 85 of the transfer paper transport belt 60 in the second modification. The light emitted from the light source 291 of the mark sensor is collimated by the collimator lens 293 as in the above embodiment. In the second modification, the light that has passed through the collimating lens 293 is split into six light beams by the slit array 294 in the moving direction (the X direction in the drawing) of the transfer paper transport belt 60. The six light beams thus divided are applied to an area of the transfer paper transport belt 60 where the mark 85 passes. The six light beams applied to the transfer paper transport belt 60 have the length in the belt movement direction (X direction in the drawing) equal to the length of each mark 85, and the light interval is equal to the mark interval. Therefore, the light-receiving start timing at which the irradiated six light passes through each mark and is received by the photodiode is the same for all the lights. The light reception end timing at which the irradiated six lights are blocked by the belt portion and are no longer received by the photodiodes is the same for all the lights. Note that the light receiving means for receiving these six lights may be individually provided, but in the second modification, a single photodiode 92 is used as in the above embodiment. In the second modification, the light passing through each of the six marks 85 is condensed by a condensing lens (not shown) and received by a single photodiode 92.

According to the second modification, even if a part of the six marks 85 through which the multi-beam light is transmitted has a cause that makes it difficult to detect the mark, the light transmitted through the remaining marks causes the mark to be difficult to detect. Detection can be performed.
Further, in the second modified example, since the output signals when a plurality of lights respectively passing through a plurality of marks are received at the same time are used, a pitch error occurring in a plurality of marks provided at a constant interval is averaged. can do. Therefore, an effect of enabling more accurate mark detection is also obtained.
In addition, as a method of irradiating a plurality of lights, a method using a plurality of light sources, a method of forming a multi-beam by diffracted light using a diffraction grating, and the like are considered, and any method may be used.

[Modification 3]
Next, still another modified example of the mark sensor according to the above-described embodiment (hereinafter, this modified example is referred to as “modified example 3”) will be described.
FIG. 12 is a schematic configuration diagram of a belt driving device 380 that drives the transfer paper transport belt 60 according to the third modification. The mark sensor 390 provided in the belt driving device 380 is a reflection type mark sensor, and the mark 385 provided on the transfer paper transport belt 60 is configured by a reflection pattern. The basic configuration of the mark sensor 390 includes a light source 391 composed of an LED (light emitting diode), a collimator lens 393 for converting the light into parallel light, and a photodiode 392, as in the above embodiment. However, since it is a reflection type mark sensor, the photodiode 392 is arranged on the same side as the light source 91 with respect to the transfer paper transport belt 60.

  Here, in the third modification, the rows of the light sources 391 and the photodiodes 392 are arranged so as to be parallel to the surface of the transfer paper transport belt 60 along a direction orthogonal to the moving direction of the transfer paper transport belt 60. ing. Therefore, both the light emitted from the light source 391 and passing through the collimating lens 393 and the light reflected by the mark 385 are in the direction orthogonal to the moving direction of the transfer paper transport belt 60. Thus, for the same reason as described with reference to FIGS. 7A and 7B, even when the distance between the mark sensor 90 and the transfer paper transport belt 60 changes, the light reception start timing by the photodiode 392 and the light reception start timing There is no change in the light reception end timing, and accurate mark detection is possible.

In the third modification, a reflective mark sensor in which the light emitting unit and the light receiving unit are configured separately is used. However, a reflective mark sensor in which the light emitting unit and the light receiving unit are integrated is used. Can also be used. In this case, even a reflective mark sensor can irradiate light from the surface normal direction of the transfer paper transport belt 60 as in the first embodiment.
Further, even when the light emitting unit and the light receiving unit have different configurations, the light can be emitted from the surface normal direction of the transfer paper transport belt 60 as in the first embodiment. Specifically, as shown in FIG. 13, the light that has passed through the collimator lens 493 is applied to the transfer paper transport belt 60 via a splitter 495 from the normal direction. Then, the reflected light vertically reflected by the mark 385 is refracted by 90 degrees by the splitter 495, and is guided to the photodiode 492 disposed on the side of the splitter 495 in the belt moving direction.

  In the configuration of the above-described embodiment, the first modified example, the second modified example, and the third modified example, in the belt width direction of the light applied to the area where the marks 85 and 385 on the transfer paper transport belt 60 pass. It is desirable that the cross-sectional length is shorter than the length of the marks 85 and 385 in the same direction. With this configuration, even if the belt is slightly meandered, all the light can pass through the mark 85 in the belt width direction. Does not fluctuate. Therefore, even if a slight belt meander occurs, stable mark detection can be performed, and stable position control can be performed.

  As described above, the belt driving device 80 provided in the laser printer according to the above-described embodiment includes a plurality of marks provided on the transfer paper transport belt 60 so as to be continuous at predetermined intervals in the movement direction of the transfer paper transport belt 60 as a belt member. The drive control device includes light sources 91, 191, 391, 491 as light irradiation means for irradiating light to 85, 385 and collimating lenses 93, 193, 393, 493. The light irradiating means in the second modification includes a light source 291 and a collimating lens 293, and also includes a slit row 294. Such a drive control device includes photodiodes 92, 392, and 492 as light receiving means for receiving transmitted light or reflected light of light emitted from a light source toward a mark. Further, a position control device is provided as speed / position control means for controlling the speed or position of the transfer paper transport belt 60 based on the output signal output from the photodiode. The light exiting from the collimator lenses 93, 193, 393, 493 or the slit row 294 is substantially parallel light. Thus, even when the position of the transfer paper conveying belt 60 in the direction normal to the surface is displaced at each mark detection timing and the detection distance fluctuates, the light reception start timing and the light reception of the light that has passed or reflected one mark by the photodiode are received. There is almost no change in the end timing. Therefore, it is possible to suppress a detection error that has conventionally occurred due to a change in the detection distance.

In the printer of the above embodiment, the light emitted from the collimating lenses 93, 193, 393, 493 or the slit rows 294 has a sectional length in the moving direction of the transfer paper transport belt 60 shorter than the interval between the marks 85, 385. Has become. As a result, as described in the above embodiment, the difference between the high level value and the low level value of the output signal output from the photodiodes 92, 392, 492 can be maximized. It can be performed.
In the first modification, light having a long cross-sectional shape in a direction (Y direction in the drawing) orthogonal to the moving direction (X direction in the drawing) of the transfer paper transfer belt 60 is used. The light is irradiated to the mark 85 of 60. Thus, as described in the first modification, stable mark detection can be performed even while the transfer paper transport belt 60 is meandering.
In the second modification, the slit row 294 is used to irradiate the plurality of marks 85 with a plurality of lights along the moving direction of the transfer paper transport belt 60. The light irradiation interval at this time is an integral multiple of the mark interval of the plurality of marks 85 provided on the transfer paper transport belt 60 so as to be continuous at a constant interval. With such a configuration, as described in the second modification, even if there is a cause that makes it difficult to detect a mark in a part of the six marks 85 that respectively pass a plurality of lights, Mark detection can be performed by light passing through the mark. Furthermore, by adopting such a configuration, as described in the second modification, the pitch errors occurring in the plurality of marks 85 provided at a constant interval can be averaged, so that more accuracy can be obtained. High mark detection is also possible.

Further, in the above embodiment, the light emitted from the collimator lenses 93, 193, 393, 493 or the slit rows 294 is irradiated from a direction orthogonal to the moving direction of the transfer paper transport belt 60. Thus, as described in the above embodiment, even if the position of the transfer paper transport belt 60 in the surface normal direction is displaced, the light reception start timing and the light reception end timing by the photodiodes 92, 392, 492 do not change. Therefore, it is possible to suppress a detection error that has conventionally occurred due to a change in the detection distance.
Further, except for the configuration shown in FIG. 12, in the above-described embodiment, since light is irradiated from the normal direction of the surface of the transfer paper transport belt 60, conventionally, the position of the transfer paper transport belt 60 in the surface normal direction is displaced. It is possible to suppress the detection error that has occurred at the time.
The laser printer according to the above-described embodiment includes the transfer paper transport belt 60 provided with a plurality of marks 85 and 385 that are continuous at predetermined intervals in the movement direction. Further, a belt driving device 80 is provided as a driving force transmitting means for transmitting the driving force for moving the transfer paper transport belt 60 to the belt. And, since the drive control device having the above-described configuration is used as the drive control means for controlling the drive of the belt drive device 80, it is possible to suppress the detection error conventionally caused by the fluctuation of the detection distance, The image quality can be maintained even if the detection distance fluctuates.

In the above-described embodiment, the drive control of the transfer paper transport belt 60 has been described as an example. However, the present invention can be similarly applied to a device that performs position control or speed control of a belt member. For example, the present invention can be applied to drive control for belt members such as a photoreceptor belt and an intermediate transfer belt.
In the above embodiment, the drive control of the transfer paper transport belt 60 in a so-called tandem type color printer has been described. However, a plurality of color developing devices 120K, 120Y, 120C, and 120M are provided around one photosensitive drum 111. Also, the present invention can be applied to position control of the intermediate transfer belt 160 of the image forming apparatus as shown in FIG. In this apparatus, a color image is obtained by sequentially superimposing and transferring each color toner image formed on the photosensitive drum 111 onto the intermediate transfer belt 160. Such a one-drum type image forming apparatus has an advantage that the number of photosensitive drums 111 is one, so that the size can be relatively reduced and the cost can be reduced. However, since a color image is formed by repeating image formation a plurality of times (usually four times) using one photosensitive drum 111, there is a disadvantage that it is difficult to increase the image formation speed. On the other hand, the tandem-type image forming apparatus as in the above-described embodiment has a plurality of photosensitive drums 11K, 11Y, 11C, and 11M, so that it is difficult to reduce the size and cost. There is an advantage that the formation speed can be easily increased. Recently, tandem-type image forming apparatuses such as those in the above-mentioned embodiments have attracted attention because color image forming apparatuses are strongly required to have an image forming speed comparable to that of a monochrome image forming apparatus.

  Further, the tandem type image forming apparatus includes a direct transfer system for directly transferring the toner image on each photoconductor 1 onto the transfer paper 100 as described in the present embodiment, and an indirect transfer system as shown in FIG. There is. In this indirect transfer method, after the toner images on the respective photosensitive drums 11 are sequentially transferred to an intermediate transfer belt 160 as an intermediate transfer body, the toner images on the intermediate transfer belt 160 are transferred to a transfer paper by a secondary transfer device 168. 100 at a time. The present invention can be applied to drive control of the intermediate transfer belt 160 in the image forming apparatus of the indirect transfer type. In the illustrated example, the secondary transfer device 168 is a transfer / conveying belt, but a roller-shaped belt may be employed.

Comparing these transfer methods, in the direct transfer method, the paper feeder must be disposed upstream in the transfer paper transport direction in which the plurality of photosensitive drums 11 are arranged, and the fixing device 7 must be disposed downstream thereof. . For this reason, there is a disadvantage that the apparatus becomes large in the transfer paper transport direction. On the other hand, in the indirect transfer method, the secondary transfer position can be relatively freely arranged. Therefore, for example, the sheet feeding device and the fixing device 7 can be arranged in a region projected from a direction (upward in the drawing) orthogonal to the direction in which the image forming units 1 are arranged, and the size can be reduced. There is. In the case of the direct transfer method, the fixing device 7 is often arranged close to the image forming unit 1K located at the most downstream in the transfer paper transport direction so as not to increase the size in the transfer paper transport direction. In this case, the fixing device 7 cannot be arranged so as to have a sufficient allowance for the transfer paper 100 to be bent, and an image is formed by an impact when the leading end of the transfer paper 100 enters the fixing device 7. This adversely affects the image formation by the means 1. This adverse effect is particularly noticeable when the transfer paper 100 is a thick sheet. Further, the speed difference between the sheet conveyance speed when passing through the fixing device 7 and the sheet conveyance speed by the transfer paper conveyance belt 60 also has an adverse effect on image formation by the image forming means 1. On the other hand, in the case of the indirect transfer method, the fixing device 7 can be arranged so as to have a sufficient margin for the transfer paper 100 to be bent. Has little effect on formation. From this viewpoint, it can be said that among the tandem type image forming apparatuses, the indirect transfer type is particularly excellent.
Needless to say, the present invention can be applied not only to a color image forming apparatus but also to a belt member such as a photosensitive belt provided in a monochrome image forming apparatus.
Further, the present invention is not limited to the belt member for image formation, and can be applied to a belt member that is required to control a moving amount per unit time or a moving position at a predetermined time with high accuracy. .

  In FIG. 18A, the “light source unit” indicated by reference numeral 700 includes a light source 701 and a lens 702 that collects light from the light source 701. The lens 702 is a “collimating lens”. The “light receiving unit” indicated by reference numeral 710 is housed in the sensor housing 720 together with the light source unit 700. The “moving body” denoted by reference numeral 800 is, for example, the above-described intermediate transfer belt, and has a scale 750 formed on the surface thereof.

  The “slit” indicated by reference numeral 730 is disposed “at a predetermined gap” from the scale 750 via the gap regulating member 740, and is provided by pressing means 760 provided between the sensor housing 720 and the slit 730. It is elastically pressed to the moving body 800 side. Therefore, the gap between the slit 730 and the scale 750 is always kept at a constant gap (the thickness of the gap regulating member 740) by the gap regulating member 740.

  As shown in FIG. 18B, the scale 750 has rectangular non-reflective portions 751 arranged in a “one-dimensional lattice shape” in the left-right direction in the figure, and portions other than the non-reflective portions 751 are provided with a reflective portion 752. Has become. The non-reflective portion 751 can be formed as a “light transmitting portion” or can be formed as a “light absorbing portion”. In the one-dimensional lattice array, the width of the non-reflective portion 751 (width in the left-right direction in the drawing) and the width of the reflective portion 752 are equal to each other.

  The slit 730 is, for example, a rectangular light shielding plate as shown in FIG. 18C, and has a rectangular opening 731 formed therein. The opening 731 transmits light, of course, but the opening 731 may be formed of a transparent material or may be formed as a hole. The shape and size of the opening 731 are the same as the shape and size of the non-reflective portion 751 in the scale 750.

  When the light source 701 in the light source unit 700 is turned on, light from the light source 701 is condensed by the lens 702 to be converted into a parallel light flux, and irradiates the slit 730. Part of the irradiation light passes through the opening 731 of the slit 730 and irradiates the scale 750 through the gap regulated by the gap regulating member 740. At this time, when the irradiation light irradiates the reflecting portion 752 of the scale 750, the reflected light passes through the opening 731 of the slit 730, enters the light receiving unit 710, and is photoelectrically converted by the light receiving unit 710.

  In this state, when the moving body 800 is displaced in the left-right direction in FIG. 18A, the “portion irradiated by the light through the opening 731 of the slit 730” of the scale 750 becomes the reflecting portion 752 and the non-reflecting portion 751. Since they alternately change, the photoelectric conversion output of the light receiving means 710 fluctuates, and the movement state (moving speed or moving distance) of the moving body 800 can be known from the fluctuation. In other words, the photoelectric conversion signal obtained from the light receiving unit 710 has a substantially sinusoidal shape, and by “rectifying” this, an “incrementable encoder signal” can be obtained.

  As the light source 701 used for the light source portion 700, a light-emitting diode (LED), a light bulb, a semiconductor laser (LD), or the like can be used. Any light source that can obtain a “reflection / non-reflection pattern” with sufficient contrast by the reflecting portion 752 and the non-reflecting portion 751 in the scale 750 can be used without any particular limitation. Although the lens 702 is not always necessary, it is preferable to use the lens 702 in order to increase the light use efficiency.

  As the light receiving unit 710, an appropriate light receiving element having sensitivity to light emitted from the light source 701 can be used.

  The reflection portion 752 and the non-reflection portion 751 of the scale 750 can be formed by, for example, using a metal reflection surface such as Al or Cr as the reflection portion 752, and forming the non-reflection portion 751 by etching. Also, a one-dimensional lattice pattern of transmission and absorption is formed by exposing and developing the photoemulsion film, and a reflective scale can be formed by forming a metal reflection surface. When the moving body 800 is in the form of a belt or a drum, and the scale 750 is provided on the surface thereof, the latter scale that can produce a scale on a resin film is easily used.

  The gap regulating member 740 is a member for keeping the gap between the slit 730 and the scale 750 constant as described above, but is fixed to the slit 730 side. Since the gap regulating member 740 comes into contact with the scale 750, it is preferable that the gap regulating member 740 has a material and a structure that does not damage the scale 750. Further, as described later, the slit itself can also serve as a gap regulating member.

  A scale having a structure in which a hole is formed in a metal as an arrangement pattern of the non-reflective portions is often used as a scale. In such a case, it is necessary to provide the gap regulating member with “an area larger than the hole of the non-reflection portion” so as not to be caught by the hole. The gap regulating member is preferably made of "a resin material having a small frictional force" or the like so as not to damage the scale.

  As the pressing member 760, a leaf spring or the like can be used in addition to the “coil spring” shown in FIG.

  In other words, the encoder device according to the embodiment illustrated in FIG. 18 is configured such that “the light from the light source unit 700 is equal to the grid width of the scale 750 on the scale 750 having portions having predetermined reflectance arranged in a one-dimensional grid. The light is radiated through a slit 730 having an opening 731 having an opening width, the light intensity of the light reflected by the scale 750 is detected by a light receiving unit 710, and the light intensity detected by the light receiving unit 710 changes. In the encoder device for detecting the displacement of the typical scale 750, the gap regulating member 740 for keeping the gap between the slit 730 and the scale 750 constant and the slit 730 are elastically attached to the scale 750 via the gap regulating member 740. (Claim 8).

  Further, the light source unit 700 and the light receiving unit 710 are housed in the sensor housing 720, and the pressing unit 760 is disposed between the sensor housing 710 and the slit 730 (claim 9).

  When the scale is formed on the surface of a belt or a drum, the scale repeats up and down movements and tilt angle changes due to waving vibrations as the moving body moves. In the encoder device of the present invention, the slit 730 and the scale 750 are Since the slit 730 is kept at a constant interval via the gap regulating member 740 and the pressing member 760 presses the slit 730 against the scale 750 at a constant pressure, even if the scale 750 moves up and down or has an inclination, the slit 730 and the scale 750 may be used. Is kept "always constant". Therefore, it is possible to reduce damage to the scale and the slit due to the contact between the scale 750 and the slit 730, and to reduce measurement errors due to gap variation and tilt angle variation.

  FIG. 19 shows another embodiment of the encoder device according to claim 8. In addition, in order to avoid complication, the same reference numerals as those in FIG. 18 are used in the drawings described below for those which are considered to be unlikely to be confused.

  In the embodiment of FIG. 19, the light from the light source unit 700 is provided with an opening having an opening width substantially equal to the grating width of the scale 750A on a scale 750A having portions having a predetermined transmittance arranged in a one-dimensional lattice. The light intensity of the light radiated through the slit 730 and transmitted through the scale 750A is detected by the light receiving means 710, and the change in the light intensity detected by the light receiving means 700 causes the displacement of the scale 750A relative to the slit 730 to change. In the encoder device for detection, a gap regulating member 740 for keeping the gap between the slit 730 and the scale 750A constant, and a pressing means 760 for elastically pressing the slit 730 to the scale 750A via the gap regulating member 740 are provided. It is an encoder device having.

  The light source 701 and the lens 702 constituting the light source unit 700 are housed in the sensor housing 720A, and the pressing unit 760 is provided between the sensor housing 720A and the slit 730. Is pressed against the scale 750A via the. The lens 702 is a collimating lens that converts light from the light source 701 into a parallel light flux. Reference numeral 800A indicates a “light-transmissive moving body”.

FIG. 20 shows an embodiment of the encoder device according to the tenth aspect.
That is, in this embodiment, the light source unit 700 and the light receiving unit 710 are housed in the sensor housing 720, and the pressing unit 760 is disposed between the base BS and the sensor housing 720, and The body 720 is pressed to the scale 750 side, and the slit 730 and the gap regulating member 740 are provided on the sensor housing 720.

  In the case of the embodiment shown in FIG. 18, when the scale 750 moves up and down, the gap between the slit 730 does not change, but the distance between the scale 750 and the light source 701 / light receiving unit 710 changes. Since the light source 701 and the light receiving means 710 have an “optical axis having an angle with respect to the scale 750”, a change in the distance from the scale 750 results in a change in the reflection distance. This can cause

  In the embodiment of FIG. 20, the slit 730 and the gap regulating member 740 are fixed to the sensor housing 720 and are closely attached to the scale 750, so that the gap between the scale 750 and the slit 730 is kept constant. In addition, the positional relationship between the light source / light receiving means and the scale is kept constant, and extremely stable signal detection is possible.

FIG. 21 shows an embodiment of the encoder device according to the eleventh aspect.
In this embodiment, the sensor housing 720 in which the light source unit 700 and the light receiving unit 710 are accommodated is held so as to be displaceable around a “position where light passing through the slit 730 is irradiated on the scale 750”.

  That is, the slide rail 772 of the rotary slide rail 770 is fixedly provided on the upper part of the sensor housing 720 (the side opposite to the side with respect to the moving body 800), and the slide rail 771 that forms a pair with the slide rail 772 is a vertical slide. It is engaged with the rail 780.

  A pressing means 760 is provided between the base BS on which the vertical slide rail 780 is fixed and the vertical slide rail 780, and applies a pressing force toward the scale 750 to the sensor housing 720 via the vertical slide rail 780. Let me.

  The center of rotation of the rotating slide rail 770 is set at a position where light emitted from the light source 701 is collected by the lens 702, passes through the opening of the slit 730, and irradiates the surface of the scale 750.

  The sensor housing 720 in which the rotation guide rail 770 is integrated can be displaced in the vertical direction in the drawing, but the position where the light from the light source unit 700 irradiates the scale 750 does not change due to the linear displacement. . Further, even when the sensor housing 720 is guided by the rotation guide rail 770 and makes a rotational movement, the “center where the light from the light source 700 irradiates the scale 750”, which is the center of rotation, is not displaced.

  In the embodiment of FIGS. 18 and 20, when the scale 750 is tilted from the illustrated position, the positional relationship between the slit 730 and the scale 750 may be shifted, but in the embodiment of FIG. The vertical slide rail 780 and the rotary slide rail 770 are used as jigs, and are installed so as to be able to move flexibly in the gap direction (the vertical direction in the figure) with the scale 750 and the rotational direction of the scale 750. Is set on the surface of the scale 750, even if the sensor housing 720 is displaced in the vertical and rotational directions within the movable range, the detection position (light emitted from the light source 701 is The position where the light is collected and illuminates the surface of the scale 750 through the opening of the slit 730 does not change.

  Further, since the sensor housing 720 is pressed against the scale 750 by the pressing means 760, the gap change between the scale 750, the sensor housing 720, and the slit 730 can be suppressed. In addition, since the “direction orthogonal to the drawing” can be considered as the direction of the inclination of the scale 750, it is more effective to use the “rotational slide rail with the detection position as the center of rotation” in this direction.

  In addition to the method using the rotating slide rail, the same effect can be obtained by the "method of fixing to a rotating shaft whose detection position is the center of rotation".

FIG. 22 shows an embodiment of the encoder device according to claim 12.
That is, in this embodiment, as shown in FIG. 22A, the light from the light source unit 700 is “scaled so as to be orthogonal to the moving direction of the scale 750 (the horizontal direction in FIG. 22A). 750.

  In the case of an optical system arrangement in which a light beam is emitted at an angle with respect to the scale 750, if the detection distance (the distance between the light source unit / light receiving unit and the surface of the scale 750) fluctuates, the light receiving unit outputs a signal indicating that the scale 750 has moved. Is obtained. As in this embodiment, if the light beam is irradiated so as to be orthogonal to the moving direction of the scale 750 (alternate arrangement direction of the reflection part and the non-reflection part), even if the detection distance fluctuates, There is no relative position change between the reflected light and the light receiving means, and no signal change occurs in the light receiving means.

  In the case of a “reflection sensor” as shown in FIG. 22, since the regular reflection light from the scale 750 is received by the light receiving means 710, it is general that the irradiation light beam and the received light beam form an angle with each other. When such a reflection type sensor is used, as shown in FIG. 22B, the irradiation light beam and the received light beam move in the direction of movement of the scale 750 (the direction orthogonal to the drawing in FIG. 22B). In a direction orthogonal to each other. In this direction (the left-right direction in FIG. 22B), the “longitudinal direction of the rectangular shape” corresponds to the reflecting portion and the non-reflecting portion as shown in FIG. 18B. Even if the irradiation position is displaced, the output of the light receiving means does not change.

  Therefore, the encoder device according to the eleventh aspect can accurately detect a signal even if the gap between the slit and the scale greatly changes such that the gap is out of the limit by the gap limiting member.

  In each of the embodiments described above, the light-collecting lens 702 is used for the light source unit 700, and the light from the light source 701 is collected and emitted to the scale 750. This lens 702 is preferably a “collimating lens” as in the above embodiments (claim 13).

  When the light applied to the scale 750 is “a divergent light beam or a convergent light beam”, the divergent light beam diverges even after passing through the slit 730, and the convergent light beam converges. For this reason, it is difficult for the light beam cross-sectional shape of the light beam after passing through the slit to maintain the “slit opening shape”.

  In such a state, when the gap between the slit and the scale has a certain size, or when the gap changes due to deformation of the gap limiting member, the light beam diameter of the light beam received by the light receiving unit changes, thereby causing a measurement error. Occurs.

  If the light beam emitted from the light source unit is a parallel light beam as in the encoder device according to claim 13, the light beam can maintain substantially the same light beam diameter even if it travels "a certain distance" after passing through the slit. Even if a change occurs, it is possible to maintain the detection accuracy.

As the light source of the encoder device, an LED is often used in terms of cost.
Ordinary LEDs have a large light-emitting area and cannot be completely collimated even when condensed using a lens because of their low spatial coherence. When a more parallel light beam is required, an "LD having a small light source area" or a point light source LED is preferably used as a light source.

FIG. 23 shows an embodiment of the encoder device according to claim 14.
In this embodiment, the slit 730A is configured as a “spring member” having an opening 731A, and one end is fixed to the sensor housing 720B to “come up with a gap regulating member and a pressing unit”. "ing.

  The “spring member” forming the slit 130 </ b> A may be a leaf spring (claim 15), or may be configured by attaching a slit to a leaf spring member, and is a “resin film”. (Claim 16). When the resin film is used as a member having spring properties, it is possible to "form a metal vapor-deposited film on a transparent film surface by vapor deposition or the like, and process and form the opening 731A in the metal vapor-deposited film by a process such as etching". 17).

  Alternatively, the resin film may be configured so as to “having an opening pattern of an absorbing portion and a transmitting portion with respect to the wavelength of light emitted from the light source portion 100” (claim 18).

  As described above, by making the slit serve both as a function of the gap regulating member and the pressing member by means of a leaf spring-shaped slit, the encoder device can be simply configured, reducing the cost and improving the assemblability. It is.

  As described above, in the encoder device of the present invention, in the encoder device of the present invention, the "gap regulating member or the slit also serving as the gap regulating member" comes into contact with the scale and is pressed to slide on the scale. In order to improve the durability, it is preferable to have "lubricating means for lubricating between the scale and the gap regulating member" (claim 19).

  As the "lubricating means", there is one suitable for the relationship between the gap regulating member and the material of the scale. For example, when the scale is a metal or the like, it may be provided as "lubricating oil" or the like between the scale and the gap regulating member. In the case of a resin scale, by forming the gap regulating member with a fluorine-containing resin such as PEFE, the gap forming member may also serve as “lubricating means”, or “the gap regulating member and the scale may be combined with each other. The lubricating means may be configured as a "lubricant applying means for applying a lubricant during" (claim 20).

  By using the lubricating means in this way, the durability of the slit and the scale can be improved.

FIG. 24 shows an embodiment of the encoder device according to claim 21.
In this encoder device, the gap regulating member 740A is formed of a “roller” and rolls on the scale. By using a freely rotatable roller as the gap regulating member 740A, the scale 750 can be hardly damaged, and at the same time, the gap between the sensor housing 720 and the scale 750 can be limited.

  As the gap regulating member, not only the roller shown in FIG. 24 but also a “ball member” can be used. When a roller or a ball member is used as the gap regulating member, the gap member can also serve as a “lubricating unit”.

  FIG. 25 is a diagram for explaining a characteristic portion of the encoder device according to claim 22. In the embodiment described above with reference to FIGS. 18 to 24, the slits 730 and 730A have a “single opening”, but the slit 130B shown in FIG. Openings 7311, 7312,... 731i,... Are provided in the grid arrangement direction of the one-dimensional grid of the scale 750 (the left-right direction in FIG. 25B). The plurality of openings 731i are arranged in the same shape and the same pitch as the non-reflective portions 751 in the scale 750 shown in FIG.

  When a plurality of openings 731i are provided like the slit 730B, even when the scale 750 is "scratched", a plurality of reflection portions and non-reflection portions of the scale can be read, so that signal detection is more stabilized. I do.

  FIG. 25C shows the cross-sectional shape of the light beam passing through the slit 730B when the slit 730B is irradiated with an elliptical light beam (indicated by LX in FIG. 25B).

  FIG. 26 shows an example in which the invention described in claim 23 is applied to the embodiment of FIG.

  That is, this embodiment has a cleaning member 735 for cleaning the scale 750. In this embodiment, the cleaning member 735 has a brush shape, and is fixed to the slit 730A near the “end on the side fixed to the sensor housing 720B” of the slit 730A that also serves as a pressing means and a gap regulating member. The tip of the brush rubs the surface of the scale 750 so that the scale 750 is always kept in a clean state.

  In this manner, the surface of the scale 750 can be constantly cleaned, and damage to the scale 750 due to “entanglement of dust or the like” on the surface can be prevented. Further, since the scale 730A also serves as the pressing means, the cleaning member 735 is also pressed against the scale 750 with a constant pressure, so that the cleaning efficiency can be kept constant.

FIG. 27 shows an embodiment of the moving device according to claim 24.
In this embodiment, the moving body 830 is an “intermediate transfer belt”, which is formed in an endless belt shape and is driven to rotate in one direction. A scale 750 is formed on one circumferential edge of the circumferential surface of the intermediate transfer belt 830 in the width direction. Reference numeral 840 denotes a “portion (including an encoder 840) that includes a light source unit, a light receiving unit, a slit, a gap regulating member, and a pressing unit, and configures an encoder device together with the scale 750”.

  When the intermediate transfer belt 830 is running, the output of the encoder 840 is input to a control unit (microcomputer, CPU, or the like) 842, and a driving unit (motor or the like) 844 for driving the intermediate transfer belt 830 is controlled by the control unit 842 by the encoder. 840, the traveling speed and traveling distance of the intermediate transfer belt 830 can be stably and accurately controlled.

FIG. 28 illustrates an example of the image forming apparatus. This image forming apparatus is for forming a color image.
A photoconductive photoconductor as a “latent image carrier” indicated by reference numeral 651 is formed in a drum shape, and is driven to rotate counterclockwise by a driving unit 651A. At the time of image formation, the photoconductor 651 rotates at a constant speed, and its peripheral surface is uniformly charged by a charging unit (not shown), and is exposed by an exposure unit (for example, an optical scanning device) not shown to form an electrostatic latent image.

  In the electrostatic latent image, black, yellow, magenta, and cyan color component electrostatic latent images corresponding to a black component image, a yellow component image, a magenta component image, and a cyan component image, which form a color image, are arranged in this order. Are sequentially formed. The black component electrostatic latent image formed first is developed with black toner by the black developing unit K in the revolver developing device to become a black toner image, and is transferred onto the intermediate transfer belt 653. The intermediate transfer belt 653 is driven to rotate clockwise by the driving unit 653A at substantially the same linear velocity as the linear velocity of the photoconductor 651.

  After the transfer of the black toner image, the black toner remaining on the photoconductor 651 is removed from the photoconductor 651 by a cleaning device (not shown), and the photoconductor 651 is discharged by a static eliminator (not shown) and then charged by a charger (not shown). The exposure forms a yellow component electrostatic latent image.

  This yellow component electrostatic latent image is developed with a yellow toner by a yellow developing unit Y of a revolver developing device 652 to become a yellow toner image, which is transferred by being superimposed on a black toner image previously transferred onto an intermediate transfer belt 653. Is done.

  In the same manner as described above, a magenta component electrostatic latent image and a cyan component electrostatic latent image are sequentially formed, and these are formed by a magenta developing unit M and a cyan developing unit C of the revolver developing device 652, respectively. And the image is transferred onto the intermediate transfer belt 653.

  In this manner, a color image in which the black, yellow, magenta, and cyan toner images are superimposed on the intermediate transfer belt 653 is obtained. The desired color image is obtained by transferring and fixing the color image from the intermediate transfer belt 653 onto a sheet-like recording medium such as transfer paper by a transfer unit (not shown).

  A scale 951 is formed on one peripheral edge of the photoconductor 651 in the axial direction, and the scale 951 is read by an encoder 952. Further, a scale 953 is formed at one peripheral portion in the width direction of the intermediate transfer belt 653, and the encoder 954 reads the scale 953.

  The scale 951 and the encoder 952, and the scale 953 and the encoder 954 each constitute an encoder device of the present invention, and more specifically, have a configuration as shown in FIGS. 18, 20 to 26.

  The running state of the peripheral surface of the photoreceptor 651 and the running state of the intermediate transfer belt 653, that is, the running speed and the running distance thereof, can be detected stably and accurately by these encoder devices. Can control. A good color image can be obtained by transferring each color toner image with high accuracy.

  FIG. 29 shows a “tandem type color image forming apparatus” as another example of the image forming apparatus.

  The color image forming apparatus includes a plurality of image forming stations 601K, 601K, 610A, 404B, 404A, 404B, 404A, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, 404B, and 404B along a transport surface of a sheet transport belt 3 that transports a transfer sheet 2 as a sheet recording medium. 601M, 601Y and 601C are arranged.

  The image forming stations 601K, 601M, 601Y, and 601C form a black toner image, a magenta toner image, a yellow toner image, and a cyan toner image in this order. Since the operation of each image forming station is the same except for the color of the toner used for development, the image forming in the image forming station 601K will be representatively described.

  In FIG. 29, the symbol K indicates black, M indicates magenta, Y indicates yellow, and C indicates cyan.

  The image forming station 601K is configured by disposing a charger 608K, an exposing device 609K, a developing device 610K, a cleaning device 611K, and the like around a drum-shaped photosensitive member 607K as a latent image carrier. The exposure device 609K is an optical scanning device that optically scans the laser light, deflects the laser light from the laser light source with a polygon mirror, and emits it as an exposure light beam via an optical system using an fθ lens, a deflection mirror, and the like.

In forming an image, the photoreceptor 607K is uniformly charged in the dark by the charger 608K, is exposed by light scanning with the exposure light 612K for writing a black component image from the exposure device 608Y, and a black component electrostatic latent image is formed. You. This black component electrostatic latent image is visualized by the black toner in the developing device 610K to become a black toner image.
Similarly, in the image forming stations 601M, 601Y, and 601C, magenta, yellow, and cyan toner images are formed on the photoconductors 607M, 607Y, and 607C, respectively.

The sheet conveying belt 3 is formed as an endless belt, is wound around a driving roller 605 and a driven roller 604, and is driven to rotate counterclockwise.
A paper feed tray 606 disposed below the sheet conveying belt 603 stores transfer paper 602, and feeds the uppermost transfer paper 602 when an image forming process is executed. The fed transfer paper 602 is electrostatically attracted to the sheet conveying belt 603 and is conveyed by the rotation of the sheet conveying belt 603. The black toner image is formed in the image forming station 601K, and the black toner image is formed in the image forming stations 601M, 601Y, and 601C. The transfer units 613K, 613M, 613Y, and 613C transfer the magenta, yellow, and cyan toner images.

  The photoconductors 607K, 607M, 607Y, and 607C after the transfer are cleaned by the cleaning devices 611K, 611M, 611Y, and 611C, respectively, in preparation for the next image forming process.

  As described above, the transfer paper 602 on which the color image is formed by the overlapping of the four color toner images is separated from the sheet conveying belt 603, and the color image is fixed by the fixing device 614, and then discharged out of the device. You.

  In the tandem type color image forming apparatus as shown in FIG. 29, the positioning error due to the linear velocity fluctuation of the sheet conveying belt and the photoconductor is caused by uneven thickness of the sheet conveying belt, eccentricity of the driving / driven roller, and speed of the driving motor. Due to unevenness or the like, as shown in FIG. 30, the image fluctuates according to a waveform having a plurality of frequency components. This causes image quality deterioration such as color shift and color change.

  By configuring the moving device of the present invention using each of the photoconductors 607K to 607C and the intermediate transfer belt 603 as a moving body, the running state of the photoconductor and the intermediate transfer belt can be accurately detected, and the running state can be controlled well. It is possible to effectively reduce the image deterioration such as the color shift or the color change of the formed color image.

FIG. 31 is a diagram for explaining a change in the size of the light beam when the scale surface changes.
In the figure, reference symbol L denotes a light source as a light projecting means, dz denotes a variation amount from a design position of a scale surface, LR denotes a magnitude of a light beam in a scale moving direction on a reference surface which is a design scale position, and LR ′ denotes a variation. The magnitude of the same light flux on the scale surface after the variation of the amount dz (hereinafter simply referred to as the size of the light beam), θb is the inclination angle of the central light of the light beam from the normal to the scale reference plane, θa is the divergence angle of the light beam, dr1 , Dr2 indicate the increase or decrease of the size of the light flux, respectively.
In the drawing, dz is assumed to be positive in the downward direction, and the amount of change from the reference plane is assumed to be the same as positive and negative.
θa is positive in the direction away from the center light.
There are a reflection light type and a transmission light type as an encoder device which constitutes a part of the belt drive control device, and a usage utilizing each characteristic is used. In many cases, fluctuations in the scale surface due to fluttering of the belt surface cause variations in encoder output. The biggest cause is that the size of the light beam impinging on the scale surface varies. The following is a general description.
In the figure, of the change from the light flux size LR to LR ′, the increase dr1 on the right side of the center light of the light flux becomes dr1 = dz × tan (θb + θa) due to a geometric relationship. Similarly, the decrease dr2 on the left side is dr2 = dz × tan (θb−θa). Therefore, the following equation holds.
LR '= LR + dr1-dr2
= LR + dz × {tan (θb + θa) -tan (θb-θa)} (1)
However, when the surface of the scale 150 is displaced upward in the figure, the expression (1) is directly satisfied by setting dz to a negative value. Although not shown in the drawings, when the light beam once spread by using a lens or the like is converged and used, the expression (1) is directly satisfied by setting θa to a negative value. dz changes within that range, with the allowable error as the limit value dzM.
These relations hold similarly whether the scale is a reflection type or a transmission type.

As shown in FIG. 31, when the luminous flux is divergent light, that is, when θa is positive, the magnitude of the luminous flux becomes minimum at the limit of dz being negative, and conversely, the magnitude of the luminous flux becomes maximum at the limit of dz being positive. become. When the light flux is convergent light, that is, when θa is negative, the situation is completely opposite to the above. Incidentally, when θa is 0, the light beam becomes parallel light, and the size of the light beam does not change with respect to vertical fluctuation of the scale.
When the size of the light beam changes due to the vertical movement of the scale, the following problems occur.

FIG. 32 is a diagram for explaining a case where the size of the light beam does not match the scale pitch.
FIG. 33 is a diagram for explaining a case where the size of the light beam matches the scale pitch.
In both figures, (a) is a conceptual diagram showing the relationship between the luminous flux and the scale pitch, and (b) is a conceptual diagram showing the sensor output.
In FIG. 32A, P1 indicates the length of one set of the non-reflective portion 151 and the reflective portion 152, which are substantially equal in width, that is, the scale pitch.
In the drawing, it is assumed that the light beam is simultaneously applied to the plurality of non-reflection portions 151 and the reflection portions 152, and the size of the light beam is larger than the integral multiple of the scale pitch P1 by a half pitch. At this time, the output of the sensor that receives the reflected light from the scale changes almost like a sine wave as the scale moves, as shown in FIG. In the case of this configuration, since the amount of light of a certain level or more is always incident on the sensor as the light receiving means, it does not become 0 even when the output becomes minimum.
In FIG. 33 (a), a state in which the belt is moved up and down to increase the luminous flux and is simultaneously applied to the plurality of non-reflective portions 151 and the reflective portions 152, and the magnitude of the luminous flux coincides with an integral multiple of the scale pitch P1. Assume. At this time, the output of the sensor receiving the reflected light from the scale is substantially constant even if the scale moves, as shown in FIG. This phenomenon becomes more remarkable as the state of FIG. 32 approaches the state of FIG.
Even when the size of the light beam is reduced due to the vertical movement of the belt, the same problem occurs when the size of the light beam is equal to an integral multiple of the scale pitch P1.

One method of avoiding these problems is to convert the light beam into a parallel light beam as shown in FIG. 1, that is, to set θa = 0 as described above. By making the light parallel, the size of the light beam does not change with the vertical movement of the belt, and the size of the light beam is set so as not to be an integral multiple of the scale pitch P1 at the design value. No problem.
Another method for avoiding the above problem is to keep the distance between the light source and the scale surface constant, that is, to always keep dz = 0, as shown in FIG. If the belt does not move up and down, the size of the luminous flux does not naturally change, and therefore, the size of the luminous flux does not coincide with an integral multiple of the scale pitch P1.

In the two avoidance methods described above, a special condition is provided so that the change due to the vertical movement of the belt on the right side of the equation (1) becomes zero, so that LR ′ = LR is always satisfied.
A general method for avoiding the above problem without giving such special conditions will be described below.
LR 'is a value that changes depending on the vertical movement of the belt, but no matter what size it is, it is sufficient that the value does not become an integral multiple of the scale pitch P1.
As described above, since both dz and θa can take positive and negative values, the minimum value of LR ′ is LR′m, the maximum value is LR′M, and the limit value of dz, that is, the maximum displacement including the positive and negative signs Is dzM, since in 正 of equation (1) only the whole sign is switched in accordance with the sign of θa, each of LR′m and LR′M is expressed as follows: .
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
... (2)
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
... (3)

Therefore, a general condition for the relationship between the size of the light beam and the scale pitch P1 not to be an integer ratio is represented by the following equation, where k is an arbitrary natural number.
k−1 <LR′m / P1 ≦ LR / P1 ≦ LR′M / P1 <k (4)
Here, the equal sign is the case where dz = 0 or θa = 0, and as a result, the equation includes the above two avoidance methods.
In principle, if equation (4) is satisfied, the sensor output should be able to detect the movement of the scale. However, again, the ratio of the luminous flux size to the scale pitch is very close to the integer values on both sides of the equation. In this case, the change in the sensor output becomes small. Therefore, the design should be such that LR / P1 = k−0.5 as much as possible, and both LR′m and LR′M are set to values in the vicinity thereof. Good to do. That is,
k-1 + d≤LR'm / P1≤LR / P1≤LR'M / P1≤kd
(However, 0 <d <0.5) (4 ′)
By giving an appropriate numerical value to d, a sufficient change in the sensor output can be obtained even at the allowable limit of dz depending on the value of d. When d is reduced, the change in the sensor output decreases, and when d is increased, the allowable error in dz decreases. Considering these, d is empirically preferably 0.1 or more and 0.4 or less.

Next, a similar problem regarding the multi-beam as shown in FIG. 11 or a plurality of slits as shown in FIG. 25 will be described.
In principle, the pitch of the multi-beam is designed to be equal to the scale pitch P1 on the scale surface in order to obtain the maximum change in the sensor output. That is, if the beam pitch in the scale arrangement direction formed by the multi-beam on the reference plane, which is the design position of the scale, is P2, then P2 = P1.
However, when the light beam is not a parallel light beam, the beam pitch P2 changes for the same reason that the size of the light beam changes due to the vertical movement of the belt. Assuming that the beam pitch changed from the design value in the variable range is the variable P2 ', P2' may be larger or smaller than P1 depending on the change in dz. Even when a mask having a plurality of slit-shaped transmission portions is used, the same problem occurs when the distance between the mask and the scale varies. Hereinafter, a multi-beam will be described as an example.

FIG. 34 is a diagram illustrating a case where the pitch of the multi-beams matches the scale pitch.
FIG. 35 is a diagram showing a case where the pitch of the multi-beam is shifted by a half pitch from the scale pitch.
In both figures, (a) shows a state where the left end of the left end beam coincides with the left end of a certain reflection part, and (b) shows a state where the left end of the left end beam coincides with the left end of the adjacent non-reflection part. (C) is a diagram showing a sensor output.
FIG. 34 shows a case where the beam pitch hits the scale as designed, and when the scale is changed from the state shown in FIG. 34A to the state shown in FIG. 34B, all reflected light is collectively received. The output of the sensor changes from a maximum value to a minimum value. Therefore, an output change as shown in FIG. 9C is obtained with the movement of the scale.
Even if the scale is a transmission type, the following description is the same as long as the sensor receives all the transmitted light collectively.

FIG. 35 shows a case where the beam pitch P2 ′ is smaller than the design value by a half pitch of the scale pitch P1, where n is the number of beams and
(N−0.5) × P2 ′ = (n−1) × P1 (5)
Becomes the relationship. Although not shown, if the pitch is increased by a half pitch,
(N−0.5) × P2 ′ = n × P1 (6)
Becomes the relationship.
Here, the left side of Expression (5) corresponds to LR ′ in Expression (1). If (n-0.5) × P2 is set for the design value P2, it corresponds to LR in the equation (1).
In such a case, even if the scale is moved, of the plurality of beams, the beam that produces the maximum reflection, the beam that produces the minimum reflection, and the beam that produces reflection between the two are always mixed. An almost constant output is always obtained from the sensor. That is, the movement of the scale cannot be detected.
In order to prevent such a state, the minimum value of P2 'is set to P2'm, and
(N−0.5) × P2′m> (n−1) × P1 (7)
And the maximum value of P2 ′ is P2′M,
(N−0.5) × P2′M <n × P1 (8)
Must be limited so as to satisfy both.

The state shown in FIG. 35A corresponds to a half cycle of the moire pitch based on the scale pitch P1 and the beam pitch P2 ′.
A general expression representing the moire pitch Pm is represented by the following expression.
1 / Pm = | 1 / P2'-1 / P1 | (9)
Solving this for Pm gives
Pm = P1 × P2 ′ / | P1-P2 ′ | (10)
It becomes.
If Pmm is expressed as P2'm where P2 'is smaller than P1, the absolute value symbol is removed.
Pmm = P1 × P2′m / (P1−P2′m) (11)
When P2 ′ is expressed as P2′M when the limit at which P2 ′ is larger than P1 is expressed as follows.
Pmm = P1 × P2′M / (P2′M−P1) (12)
It becomes. Since the vertical movement of the belt is assumed to be symmetrical with respect to the design value, the denominators of the equations (11) and (12) are equal to each other. Therefore, Pmm ≧ Pmm holds.

Using the moiré pitch Pm, a relational expression corresponding to the expression (4) is shown as a conditional expression for preventing the size of the luminous flux shown in the expressions (2) and (3) from becoming an integral multiple of a half pitch of the moiré.
j-1 <LR'm / (Pmm / 2) <j (13)
And,
j-1 <LR'M / (PmM / 2) <j (14)
It becomes. Here, j is an arbitrary natural number. Θa is set to one half of the angle formed by the outermost rays of the beam, and θb is set to the angle formed by the center line of the angle formed by the outermost rays of the beam with the scale reference plane.
That is, both equations must be satisfied simultaneously for the same j. Otherwise, depending on the value of dz, there will be a position where the size of the light beam is an integral multiple of the half pitch of the moiré.
In general, the moire period becomes larger as the pitches of P1 and P2 'are closer, and becomes infinity when both are equal. Therefore, it is not practical to increase the value of j. Considering that P1 = P2 in principle, it is most practical to set j = 1.

Assuming that j = 1, LR′m, LR′M, Pmm, Pmm, etc. are substituted, and the equations (13) and (14) are modified.
P2′m> P1 × (2n−2) / (2n−1) (15)
P2′M <P1 × 2n / (2n−1) (16)
Is obtained. Both equations can also be obtained directly by modifying equations (7) and (8). Note that j-1 on the left side of both equations (13) and (14) is 0 when j = 1, and when the moire period is infinite, ie, P2 '= P1, and the belt varies. Equivalent to not having Taking this into account, the two equations can be summarized as follows. If the beam pitch in all states is expressed as P2 ',
(2n-2) / (2n-1) <P2 '/ P1 <2n / (2n-1) (17)
Or
1-1 / (2n-1) <P2 '/ P1 <1 + 1 / (2n-1) (17')
It becomes.

When the scale pitch P1 is determined, the allowable variation width of the beam pitch is uniquely determined by this equation in relation to the number of beams. As a simple example, when the number of beams is three, that is, when n = 3, the equation (17) becomes:
4/5 <P2 '/ P1 <6/5
That is,
0.8 <P2 '/ P1 <1.2
It becomes.
Therefore, the range of the value of P2 'is determined. By referring to the equation (1), if the tolerance of dz is determined, for example, when θa is other than 0, the allowable value is determined.
In principle, if Expression (17) is satisfied, the sensor output should be able to detect the movement of the scale. However, if the beam pitch becomes very close to the value of the fractional expression on both sides of the same expression, again. Since the change in the sensor output becomes small, P2 '/ P1 is set as close to 1 as possible. For example, in the expression (17 ′),
1−e / (2n−1) ≦ P2 ′ / P1 ≦ 1 + e / (2n−1) (17 ″)
(However, 0 <e <1)
If an appropriate numerical value is given to e, a sufficient change in the sensor output can be obtained even at the allowable limit of dz depending on the value of e. When e is increased, the change in the sensor output is reduced, and when e is reduced, the allowable error in dz is reduced. Taking these into consideration, empirically, e is preferably 0.2 or more and 0.8 or less.

  Even when a mask having a plurality of slit-shaped transmission portions is used, when the distance between the mask and the scale varies, the same method as in the case of the multi-beam can be applied. In this case, the number n of the beams corresponds to the number p of the slits, and the beam pitch P2 corresponds to the scale formed by the plurality of beams transmitted through the slits on the reference plane which is the designed position of the scale. Since the pitch becomes the pitch in the arrangement direction, this is also referred to as beam pitch P3. However, in this case, only when the scale is of a transmission type. This is because if the reflection type is used, if dz is not 0, the reflected light reaches the mask again, a part of the beam is cut off, and correct detection cannot be performed.

FIG. 2 is a schematic configuration diagram of a mark sensor provided in a belt driving device in the laser printer according to the embodiment. FIG. 2 is a schematic configuration diagram of the laser printer. FIG. 2 is an enlarged view showing a schematic configuration of an image forming unit of the laser printer. FIG. 2 is a schematic configuration diagram of a transfer unit of the laser printer. FIG. 2 is a schematic configuration diagram of a belt driving device that drives a transfer paper transport belt of the laser printer. (A) is a graph which shows the waveform of the output signal output from the photodiode of the same mark sensor. 2B is a graph showing a signal waveform pulsed by the threshold shown in FIG. (A) shows how the optical path changes when the transfer paper transport belt is displaced when the optical path of the mark sensor is inclined in a direction perpendicular to the travel direction of the transfer paper transport belt. FIG. FIG. 3B is an explanatory diagram illustrating a state of a change in the optical path when the transfer paper transport belt is displaced when the optical path of the mark sensor is orthogonal to the moving direction of the transfer paper transport belt. FIG. 2 is a functional block diagram showing a schematic configuration of a position control device of the belt drive device. FIG. 4 is a control block diagram illustrating control performed by the position control device to grasp an actual rotation position of the transfer paper transport belt. FIG. 9 is an explanatory diagram illustrating a state in which light from a light source is applied to a mark on a transfer paper transport belt according to a first modification. FIG. 11 is an explanatory diagram illustrating a state in which light from a light source is applied to a mark on a transfer paper transport belt according to a second modification. FIG. 13 is a schematic configuration diagram of a belt driving device that drives a transfer paper transport belt according to a third modification. The schematic block diagram which shows the other example of a structure of the mark sensor of the same belt drive device. FIG. 2 is an explanatory diagram illustrating an example of a drum type image forming apparatus. FIG. 1 is an explanatory diagram illustrating an example of a tandem image forming apparatus employing an indirect transfer method. FIG. 4 is a schematic configuration diagram illustrating a belt driving device that drives a conventional belt member. (A) And (b) is an enlarged view showing a portion of a belt member facing a mark sensor. (C) and (d) are graphs showing output waveforms of the mark sensor corresponding to FIGS. (A) and (b), respectively. FIG. 2 is a diagram for describing one embodiment of an encoder device. It is a figure for explaining another embodiment of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining the characterizing portion of other embodiments of an encoder device. It is a figure for explaining other embodiments of an encoder device. It is a figure for explaining one Embodiment of a moving device. FIG. 2 is a diagram illustrating an example of an image forming apparatus. FIG. 9 is a diagram for explaining another example of the image forming apparatus. FIG. 4 is a diagram illustrating an example of a positioning error of a sheet conveying belt. It is a figure for explaining change of the size of a light flux when a scale surface fluctuates. It is a figure for explaining the case where the size of a light flux does not correspond to a scale pitch. It is a figure for explaining the case where the size of a bundle corresponds to a scale pitch. FIG. 4 is a diagram illustrating a case where a pitch of a multi-beam matches a scale pitch. FIG. 6 is a diagram showing a case where the pitch of the multi-beam is shifted by a half pitch from the scale pitch.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Image forming means 11,111 Photoreceptor drum 60 Transfer paper conveyance belt 81 Belt drive motor 82 Position control device 90 Mark sensor 91,191,291,391,491 Light source 92,392,492 Photodiode 93,193,293,393 , 493 Collimating lens 160 Intermediate transfer belt 294 Slit row 495 Splitter 100 Light source unit 110 Light receiving unit 130 Slit 131 Opening 140 Gap regulating member 150 Scale 200 Moving body

Claims (38)

  Light irradiating means for irradiating light to a plurality of marks provided on the belt member so as to be continuous at predetermined intervals in a moving direction of the belt member stretched over the plurality of support members; and Light-receiving means for receiving transmitted light or reflected light of light emitted toward the light-receiving section, and speed / position control means for performing speed control or position control of the belt member based on an output signal output from the light-receiving means. Wherein the light irradiated from the light irradiation means is substantially parallel light.   2. The drive control device according to claim 1, wherein the light irradiating unit irradiates light having a sectional length in a moving direction of the belt member shorter than an interval between the plurality of marks.   3. The drive control device according to claim 1, wherein the light irradiating unit irradiates light having a long cross-sectional shape in a direction orthogonal to a moving direction of the belt member. 4.   4. The drive control device according to claim 1, wherein the light irradiating unit irradiates the plurality of marks with a plurality of lights along a moving direction of the belt member. A drive control device wherein the irradiation interval is an integral multiple of a mark interval of a plurality of marks provided on the belt member so as to be continuous at a constant interval. The drive control device according to claim 1, 2, 3, or 4,
The drive control device, wherein the light irradiating unit irradiates light from a direction orthogonal to a moving direction of the belt member.   6. The drive control device according to claim 5, wherein the light irradiation unit irradiates light from a normal direction of a surface of the belt member.   A belt member provided with a plurality of marks continuous at predetermined intervals in the moving direction, a driving force transmitting unit for transmitting a driving force for moving the belt member to the belt member, and a driving force transmitting unit. 7. An image forming apparatus comprising: a drive control unit for performing drive control; wherein the drive control unit according to claim 1, 2, 3, 4, 5, or 6 is used as the drive control unit. .   A scale having portions having a predetermined reflectance or transmittance arranged in a one-dimensional grid pattern is irradiated with light from a light source through a slit having an opening having an opening width substantially equal to the grid width of the scale. Detecting light intensity of light reflected by the scale or light transmitted through the scale by a light receiving unit, and detecting displacement of the scale relative to the slit by a change in light intensity detected by the light receiving unit. In the encoder device, a gap regulating member for keeping a gap between the slit and the scale constant, and a pressing means for elastically pressing the slit to the scale via the gap regulating member are provided. Encoder device.   9. The encoder device according to claim 8, wherein the light source unit and the light receiving unit are housed in a sensor housing, and the pressing unit is provided between the sensor housing and the slit.   9. The encoder device according to claim 8, wherein the light source unit and the light receiving unit are housed in the sensor housing, the pressing unit presses the sensor housing toward the scale, and the slit and the gap regulating member are disposed in the sensor housing. An encoder device characterized by the above-mentioned.   11. The encoder device according to claim 8, wherein the sensor housing accommodating the light source unit and the light receiving unit is displaceably held around a position where light passing through the slit is irradiated on the scale. An encoder device characterized in that:   The encoder device according to any one of claims 8 to 11, wherein light from a light source unit is applied to the scale so as to be orthogonal to a moving direction of the scale.   The encoder device according to any one of claims 8 to 12, wherein the light source unit includes a collimating lens that collimates light emitted from the light source.   14. The encoder device according to any one of claims 8 to 13, wherein the slit is configured as a springy member having an opening, and serves as both a gap regulating member and a pressing unit.   15. The encoder device according to claim 14, wherein the member having a spring property is a leaf spring.   15. The encoder device according to claim 14, wherein the member having a spring property is a resin film.   17. The encoder device according to claim 16, wherein the resin film has a metal vapor-deposited film on a transparent film surface, and an opening is formed in the metal vapor-deposited film.   17. The encoder device according to claim 16, wherein the resin film has an opening pattern formed by an absorbing portion and a transmitting portion with respect to a wavelength of light emitted from the light source portion.   The encoder device according to any one of claims 8 to 17, further comprising a lubricating means for lubricating between the scale and the gap regulating member.   20. The encoder device according to claim 19, wherein the lubricating means is a lubricant applying means for applying a lubricant between the gap regulating member and the scale.   21. The encoder device according to any one of claims 8 to 20, wherein the gap regulating member is formed of a roller or a ball member, and is in rolling contact with the scale.   22. The encoder device according to any one of claims 8 to 21, wherein the slit has a plurality of openings in a grid array direction of a one-dimensional grid of the scale.   23. The encoder device according to claim 8, further comprising a cleaning member for cleaning the scale.   A moving device that runs on a peripheral surface of a moving body formed in a belt shape or a drum shape, comprising: the encoder device according to any one of claims 8 to 23, wherein a scale of the encoder device is formed on the moving body. Mobile device characterized by the above-mentioned.   An image forming apparatus comprising the moving device according to claim 24. A scale in which a reflecting portion and a non-reflecting portion or a transmitting portion and a non-transmitting portion are alternately arranged in a one-dimensional manner with substantially equal widths, a mechanism for moving the scale in the arrangement direction, and a light projection for irradiating the scale with a light beam Means, a light receiving means for detecting reflected light or transmitted light from the scale, and an encoder device for detecting displacement of the scale in the arrangement direction by an output of the light receiving means,
The pitch of the scale is P1, the size of the luminous flux from the light emitting means on the reference plane, which is a design position of the scale, in the arrangement direction is LR, and the scale generated during the movement of the scale is LR. When the maximum displacement amount in the direction perpendicular to the scale surface is dzM, the irradiation angle of the center light of the light beam with respect to the normal line of the reference surface is θb, the divergence angle of the light beam is θa, and k is a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
K-1 <LR'm / P1≤LR / P1≤LR'M / P1 <k
An encoder device characterized by satisfying the following relationship:   27. The encoder device according to claim 26, wherein LR / P1 = k-0.5. A scale in which a reflecting part and a non-reflecting part or a transmitting part and a non-transmitting part are alternately arranged one-dimensionally with substantially equal widths, a mechanism for moving the scale in the arrangement direction, and a plurality of beams equally spaced on the scale A light emitting means for irradiating light, and a light receiving means for detecting reflected light or transmitted light from the scale, and an encoder device for detecting a displacement of the scale in the arrangement direction by an output of the light receiving means,
The pitch of the scale is P1, the pitch in the arrangement direction formed by the plurality of beams on the reference plane, which is the design position of the scale, is P2, and the pitch is perpendicular to the scale plane generated while the scale is moving. When the maximum displacement amount from the reference plane in any direction is dzM, the irradiation angle of the center light of the beam with respect to the normal line of the reference plane is θb, the divergence angle of the beam is θa, and j is a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
And P2′m is the minimum pitch of the beam, P2′M is the maximum pitch of the beam, and the moire pitch between the scale pitch and
Pmm = P1 × P2′m / (P1−P2′m)
PmM = P1 × P2′M / (P2′M−P1)
And put
j-1 <LR'm / (Pmm / 2) <j
And,
j-1 <LR'M / (PmM / 2) <j
An encoder device characterized by satisfying the following relationship: 29. The encoder device according to claim 28, wherein n is the number of beams, and P2 ′ is a beam pitch of a variation range.
(2n-2) / (2n-1) <P2 '/ P1 <2n / (2n-1)
An encoder device characterized by satisfying the following relationship:   30. The encoder device according to claim 28, wherein P2 = P1. A scale in which transmissive parts and non-transmissive parts are alternately arranged one-dimensionally with substantially equal widths, a mechanism for moving the scale in the arrangement direction, a light projecting means for irradiating the scale with a light beam, and the light projecting means. A mask having a plurality of slit-shaped transmitting portions provided between the scale and light receiving means for detecting transmitted light from the scale, and detecting displacement of the scale in the arrangement direction by an output of the light receiving means Encoder device,
The pitch of the scale is P1, the pitch in the arrangement direction formed by a plurality of beams transmitted through the plurality of slits on a reference plane, which is a design position of the scale, is P3, and the scale is generated during movement. The maximum displacement from the reference plane in a direction perpendicular to the scale surface is dzM, the irradiation angle of the center light of the light beam with respect to the normal line of the reference surface is θb, the divergence angle of the beam is θa, and j is As a natural number,
LR′m = LR− | dzM × {tan (θb + θa) −tan (θb−θa)} |
LR′M = LR + | dzM × {tan (θb + θa) −tan (θb−θa)} |
And P3′m is the minimum pitch of the beam, P3′M is the maximum pitch of the beam, and the moire pitch generated between the scale pitch and
Pmm = P1 × P3′m / (P1-P3′m)
PmM = P1 × P3′M / (P3′M−P1)
And put
j-1 <LR'm / (Pmm / 2) <j
And,
j-1 <LR'M / (PmM / 2) <j
An encoder device characterized by satisfying the following relationship: The encoder device according to claim 29, wherein p is the number of slits, and P3 'is a beam pitch of a variation range.
(2p-2) / (2p-1) <P3 '/ P1 <2p / (2p-1)
An encoder device characterized by satisfying the following relationship:   33. The encoder device according to claim 31, wherein P3 = P1.   The encoder device according to any one of claims 26 to 33, wherein dzM is always set to 0.   35. The encoder device according to claim 26, wherein θa = 0.   36. The encoder device according to claim 26, wherein θb = 0.   A moving device having the encoder device according to any one of claims 26 to 36 and running on a peripheral surface of a moving member formed in a belt shape or a drum shape, wherein the scale of the encoder device is the moving member. A moving device formed on a peripheral surface of a moving device. An image forming apparatus comprising the moving device according to claim 37.

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