JP2007079490A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stably detecting a belt member by a light reflection sensor. <P>SOLUTION: In the image forming apparatus including the belt member which is stretched between at least two stretching rollers of a driving roller and a driven roller and is turned and the light reflection sensor which detects the belt member, a support member 501 supporting an intermediate transfer belt 8 is provided between two stretching rollers (only one roller 12 is shown), and the light reflection sensor 40 is disposed in a position F 0.5 to 10mm below an end part of a range of contact between the support member 501 and the intermediate transfer belt 8 in a belt turning direction and detects the belt member. This sensor position is within a range wherein the intermediate transfer belt 8 hardly oscillates in a vertical direction, and is not affected by eccentricity of the support member 501. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

JP 2002-72574 A JP 2004-326085 A

  As an image forming apparatus such as a copying machine, a printer, and a facsimile machine, a photoreceptor unit on which a toner image is formed, an intermediate transfer unit to which the toner image on the photoreceptor is transferred, and toner on a transfer belt of the intermediate transfer unit And a toner adhesion amount detection means for detecting the adhesion amount. After a patch pattern (reference pattern) for toner adhesion amount detection is formed on the photosensitive member and this pattern is transferred to the intermediate transfer member, the toner adhesion amount detection is performed. Some devices detect the toner adhesion amount, and control the image forming conditions (image density, color shift, etc.) based on the detection result.

  As the toner adhesion amount detection means, a light reflection sensor is widely used. In general, the light reflection sensor needs to accurately adjust the focal length with the object to be measured. If the focal distance with the object to be measured is deviated, the sensor characteristics change and the pattern detection accuracy decreases. As a result, the image formation is greatly affected. Therefore, it is necessary to keep the measured object in a stable state at the light reflection sensor detection timing.

  However, when the patch pattern on the intermediate transfer belt is detected by the light reflection sensor, the sensor output fluctuates due to the vibration or surface property of the belt that is the detection surface, and image density control and color misregistration control may become unstable. there were.

In order to solve this, the following methods have been implemented or proposed.
1) The light reflection sensor is detected on a suspension roller with little belt vibration.
2) Light reflection sensor detection is performed in a range where the belt normal intersects the suspension roller (Patent Document 1).
3) A support member is disposed between the suspension rollers, and the light reflection sensor is detected on the support member (Patent Document 2).

  However, in the case of 1), although the sensor output fluctuation due to the vibration of the intermediate transfer belt is small, a sharp peak appears in the sensor output when foreign matter is sandwiched between the intermediate transfer belt and the suspension roller. Further, when the parallelism of the suspension roller is not sufficient, there is a problem that the sensor output fluctuates with the suspension roller rotation cycle due to the eccentricity when the suspension roller rotates.

  In the case of 2), since there is no opposite object on the lower side of the intermediate transfer belt, it is difficult to make unevenness on the belt surface, and since there is a suspension roller in the vicinity, there is an advantage that the vertical vibration amount of the belt is reduced. When attaching a stopper guide so that the suspension roller of the transfer belt does not slip sideways (providing a rail-shaped guide for the entire circumference of the belt on both ends of the belt), belt vibration occurs when the joint of the stopper guide passes through the suspension roller. Under the condition 2), a sharp peak appears in the sensor output every belt cycle.

  In the case of 3), there is an advantage that the focal distance between the intermediate transfer belt and the light reflection sensor is constant. However, as in the case of 1), when the parallelism of the support member is not sufficient, Due to the knitting center, there is a problem that the sensor output fluctuates with the support member rotation period.

  An object of the present invention is to solve the above-described problems in a conventional image forming apparatus and to provide an image forming apparatus that can stably detect a belt body with a light reflection sensor.

  According to the present invention, there is provided an image forming apparatus including a belt body that is rotated by being suspended by at least two suspension rollers of a driving roller and a driven roller, and a light reflection sensor that detects the belt body. A support member for supporting the belt body is provided between the two suspension rollers, and the light reflection is performed at a position of 0.5 to 10 mm downstream from the end of the contact range of the support member and the belt body in the belt rotation direction. This can be solved by detecting the sensor.

Further, it is preferable that the support member is slightly bite into the belt body so that an angle formed by the belt body before and after the support member is 1 to 14 degrees.
The support member is preferably cylindrical.

  Moreover, it is preferable that the support member has a small-diameter portion in which the diameter of the portion not corresponding to the diameter of the portion corresponding to the detection of the light reflection sensor in the axial direction is reduced by about 0.1 to 1 mm.

The support member is preferably rotatable.
The support member is preferably fixed.
In addition, it is preferable that the light reflection sensor is disposed in an inclined manner in accordance with the inclination of the belt body at a portion where the light reflection sensor is detected.

In addition, it is preferable to provide a second support member on the downstream side of the position where the light reflection sensor detects.
Preferably, the reference pattern formed on the belt body is detected by the light reflection sensor, and the image forming conditions are controlled based on the detection result.

  According to the image forming apparatus of the present invention, the support member that supports the belt body is provided between the two suspension rollers, and the end of the contact range between the support member and the belt body is 0.5 to the downstream in the belt rotation direction. Since the light reflection sensor is detected at a position of 10 mm, the light reflection sensor can be detected within a range where the vertical vibration of the belt body is unlikely to occur and is not affected by the knitting center of the support member. it can. Therefore, accurate and stable detection can be performed.

  In addition, by arranging the support member so as to slightly bite the belt body so that the angle formed by the belt body before and after the support member is 1 to 14 degrees, the support member and the belt after the end of the nip range. It is possible to create a range where vertical vibrations are unlikely to occur.

In addition, providing the support member with a small diameter portion has the effect of concentrating the vibration of the belt body on the small diameter portion and reducing the vibration at the light reflection sensor detection position. Also, the light reflection sensor is tilted according to the inclination of the belt body. Therefore, even when the light reflection sensor has a characteristic sensitive to the tilt angle, good detection can be performed.

  Further, by providing the second support member on the downstream side of the position where the light reflection sensor is detected, it is possible to suppress the vertical vibration of the belt body that occurs downstream of the light reflection sensor detection position.

  Further, the reference pattern formed on the belt body is detected by the light reflection sensor, and the image forming conditions are controlled based on the detection result, so that the reference pattern carried on the belt body can be accurately detected, and the image forming conditions It is possible to obtain an excellent image quality by appropriately controlling the image quality.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of an electrophotographic printer as an example of an embodiment of an image forming apparatus to which the present invention is applied. First, the basic configuration of the printer of this example will be described.

  The printer 100 shown in FIG. 1 includes four process cartridges 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Yes. These use Y, M, C, and K toners of different colors as image forming substances, but the other configurations are the same, and can be replaced when the lifetime is reached.

  The process cartridge 6Y for generating a Y toner image will be described as an example. As shown in FIG. 2, a drum-shaped photosensitive member 1Y, a drum cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, and a developing device 5Y. Etc. The process cartridge 6Y can be attached to and detached from the main body of the printer 100 so that consumable parts can be replaced at a time.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1 </ b> Y is exposed and scanned by the laser beam L to carry a Y electrostatic latent image. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. Then, intermediate transfer is performed on the intermediate transfer belt 8. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. Further, the static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other process cartridges 6M, 6C, and 6K, M, C, and K toner images are similarly formed on the photoreceptors 1M, 1C, and 1K, and are intermediately transferred onto the intermediate transfer belt 8.

  In FIG. 1, an exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, 6K in the drawing. The exposure device 7 serving as a latent image forming unit irradiates the respective photoconductors in the process cartridges 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The exposure device 7 irradiates the photoconductor with a laser beam (L) emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor.

  On the lower side of the exposure apparatus 7 in the figure, paper supply means having a paper storage cassette 26, a paper supply roller 27 incorporated in these, and the like are disposed. The paper storage cassette 26 stores a plurality of transfer papers P as recording bodies, and a paper feed roller 27 is brought into contact with the uppermost transfer paper P. When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the rollers of the registration roller pair 28. The registration roller pair 28 rotationally drives both rollers to sandwich the transfer paper P, but temporarily stops rotating immediately after sandwiching. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing. In the sheet feeding unit having such a configuration, a conveying unit is configured by a combination of the sheet feeding roller 27 and the registration roller pair 28 corresponding to the timing roller. This transport means transports the transfer paper P from a paper storage cassette 26 serving as a storage means to a secondary transfer nip described later.

  Above the process cartridges 6Y, 6M, 6C, and 6K, an intermediate transfer unit 15 that moves the intermediate transfer belt 8 as an intermediate transfer member endlessly while stretching is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit 15 includes four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a cleaning device 10, and the like. A secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14 and the like are also provided. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these three rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner from the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips, respectively. Yes. In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, 1M, 1C, and 1K. , K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip. Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.

  In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side. . When the transfer paper P sent out from the secondary transfer nip passes between the rollers of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. Thereafter, the transfer paper P is discharged out of the apparatus through a pair of paper discharge rollers 29. A stack unit 30 is formed on the upper surface of the printer body, and the transfer paper P discharged outside the apparatus by the discharge roller pair 29 is sequentially stacked on the stack unit 30.

  Although not shown in FIG. 1, a reflection type photosensor 40 as an image density detecting means is disposed to face the intermediate transfer belt 8 (this will be described later with reference to FIG. 11). 8 is configured to output a signal corresponding to the light reflectivity on 8. In this reflection type photosensor, whichever of the diffused light detection type or the regular reflection light detection type, the difference between the reflected light amount on the surface of the intermediate transfer belt 8 and the reflected light amount of a reference pattern image to be described later can be made a sufficient value. Is used. The role of the reflective photosensor 40 will be described later.

Next, calibration in the printer 100 of this example will be described.
FIG. 3 is a block diagram showing a part of the electric circuit of the laser printer 100. In the figure, the control unit 150 includes toner image forming units 6Y, 6M, 6C, and 6K, an optical writing unit 7, a paper feed cassette 26, a registration roller pair 28, a transfer unit 15, and a reflective photosensor 40, which are electrically connected. Control etc. The control unit 150 includes a CPU 150a that controls the arithmetic unit and the like, and a RAM 150b that stores data.

  The control unit 150 is configured so that each toner image forming unit 6 has a predetermined timing such as when a main power supply (not shown) is turned on, when waiting after a predetermined time has elapsed, or when waiting for a predetermined number of prints to be output. It is configured to test image forming performance such as image forming performance.

  Specifically, when this predetermined timing comes, first, the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged while rotating. With respect to this charging, unlike the uniform charging (for example, −700 V) during normal printing, the potential is gradually increased. Then, development is performed by the developing devices 5Y, 5M, 5C, and 5K while forming an electrostatic latent image for a reference pattern image by scanning with the laser beam. By this development, bias development pattern images of the respective colors are formed on the photosensitive drums 1Y, 1M, 1C, and 1K. During development, the control unit 150 performs control so that the value of the developing bias applied to the developing roller 51 of each developing device 5 is gradually increased.

  The bias development pattern images of these colors are transferred so as to be arranged on the intermediate transfer belt 8 without overlapping. By this transfer, a patch pattern constituted by a reference pattern image of each color is formed on the intermediate transfer belt 8.

  When the reference image of each reference pattern image in the patch pattern passes through a position facing the light reflection sensor 40 (FIG. 11) along with the endless movement of the intermediate transfer belt 8, the light reflection amount is detected. The electric signal is output to the control unit 150. The control unit 150 calculates the light reflectance of each reference image based on the output signals sequentially sent from the light reflection sensor 40, and stores them in the RAM 150a as density pattern data. The patch pattern that has passed through the position facing the light reflection sensor 40 is cleaned by the cleaning device 10.

  FIG. 4 is a schematic diagram showing the reference pattern image P (Py, Pm, Pc, Pk). In the figure, the reference pattern image P is composed of three reference images arranged at intervals of 15 mm. In this laser printer, each reference image 101 is 15 mm long × 15 mm wide and is formed through a 15 mm gap. Therefore, the lengths of the reference pattern images Py, Pm, Pc, and Pk on the intermediate transfer belt 8 are L2 = 75 mm, respectively. The reference pattern images Py, Pm, Pc, and Pk are transferred so as to be arranged on the intermediate transfer belt 8 without overlapping, unlike the toner images of the respective colors formed during the printing process. By such transfer, one patch pattern PB constituted by the reference pattern images Py, Pm, Pc, Pk of each color is formed on the intermediate transfer belt 8.

  FIG. 5 is a schematic diagram showing the installation pitch of the photosensitive drum 1. As illustrated, the photosensitive drums 1Y, 1M, 1C, and 1K are set to L1 = 90 mm, respectively. As described above, the length L2 of each of the reference pattern images Py, Pm, Pc, and Pk is 75 mm, which is shorter than the installation pitch L1 of the photosensitive drum 1. For this reason, the reference pattern images Py, Pm, Pc, and Pk can be independently transferred so as not to overlap the respective end portions.

  FIG. 6 is a schematic diagram showing the patch pattern formed on the intermediate transfer belt 8. This figure is for explaining how the patch pattern formed on the intermediate transfer belt 8 is read by the light reflection sensor. In this figure, the patch pattern is read by the light reflection sensor 40 arranged at a position different from the present invention. explain.

  Two patch patterns PB composed of four reference patterns Pk, Pc, Pm, and Py are formed on the intermediate transfer belt 8. Specifically, a patch pattern PB1 composed of reference pattern images Pk1, Pc1, Pm1, and Py1 and a patch pattern PB2 composed of reference pattern images Pk2, Pc2, Pm2, and Py2 are formed.

  The patch patterns PB1 and PB2 are formed as follows. That is, the control unit 150 determines that the most upstream reference pattern Py1 is the most downstream from the time when the reference pattern images Pk1, Pc1, Pm1, and Py1 in the first patch pattern PB1 are transferred to the intermediate transfer belt 8. The reference pattern image moves on the intermediate transfer belt 8 until it passes through the transfer nip of the side photosensitive drum 1K.

  Further, the control unit 150 forms the respective reference pattern images Pk2, Pc2, Pm2, and Py2 of the second patch pattern PB2 on the photosensitive drums 1Y, 1M, 1C, and 1K at a predetermined timing. Specifically, the predetermined timing means that the rear end (reference pattern image Py1) of the first patch pattern PB1 has moved by a predetermined amount after passing through the transfer nip of the most downstream photosensitive drum 1K. From this point in time, the reference pattern images Pk2, Pc2, Pm2, and Py2 of the patch pattern PB2 start to be transferred onto the intermediate transfer belt 8.

  In FIG. 6, a light reflection sensor 40 as an image detecting means is disposed on the upper right side of the transfer unit including the intermediate transfer belt 8 (different from the present invention). Each reference pattern image on the intermediate transfer belt 8 is moved with endless movement, detected by the light reflection sensor 40, and then removed by the transfer unit cleaning device 10 (FIG. 1).

  The light reflection sensor 40 detects the amount of light reflected from each reference image 101 constituting the reference pattern images Pk1, Pc1, Pm1, and Py1 from the front end to the rear end of the first patch pattern PB1 in the following order. To do. That is, in order of three reference images 101 of the reference pattern image Pk1, three reference images 101 of the reference image Pc1, three reference images 101 of the reference image Pm1, and three reference images 101 of the reference image Py1. Detect. At this time, a voltage signal corresponding to the light reflection amount of each reference image 101 is detected by a method described later and sequentially output to the control unit 150. Based on the voltage signals sequentially sent from the light reflection sensor 40, the control unit 150 sequentially calculates the image density of each reference image 101 and stores it in the RAM 150b. The light reflection sensor 40 is desirable in that a diffused light detection type can detect a high density portion of the color toner.

Here, the influence of the belt in detecting the reference image will be described.
FIG. 7 shows an intermediate transfer unit before reflecting the present invention. The light reflection sensor 40 has a focal length of 5.0 mm. A suspension roller 12 having a diameter of 17.45 mm was used.

The graph of FIG. 8 shows the output of the light reflection sensor 40 when the detection positions of the light reflection sensor 40 are points A, B, and C with respect to the position of the suspension roller 12.
When detecting at point A, since the detection position is too far from the suspension roller 12, the belt 15 is affected by vibration in the vertical direction, and the output of the light reflection sensor 40 becomes unstable.

  When the detection is performed at point C, the output fluctuation of the light reflection sensor 40 due to the vibration of the intermediate transfer belt 8 is small. However, if the parallelism of the suspension roller 12 is not adjusted with considerable accuracy, it is affected by the rotational eccentricity of the suspension roller 12, and the light The output of the reflection sensor 40 varies with the rotation period of the suspension roller 12. In addition, over time, when foreign matter is caught between the intermediate transfer belt 8 and the suspension roller 12, a sharp peak may appear in the sensor output.

  In the case of detection at point B, there is no object on the lower side of the intermediate transfer belt 8, so that it is difficult to make unevenness on the belt surface, and since there is a suspension roller 12 in the vicinity, there is an advantage of reducing the vertical vibration amount of the belt. However, as shown in FIGS. 9 and 10, when the intermediate transfer belt 8 is affixed with a detent guide 401 (a rail-shaped guide for the entire circumference of the belt is provided at both ends of the belt) so that the intermediate transfer belt 8 is not laterally displaced from the suspension roller 12. When the guide seam 402 passes the suspension roller, the belt vibrates, and a sharp peak appears in the output of the light reflection sensor 40 for each belt period.

  Therefore, according to the present invention, the support member 501 (FIG. 11) is disposed between the suspension rollers 12 and 13 on which the intermediate transfer belt 8 is stretched, and the detection position of the light reflection sensor 40 is optimized.

The structure for stabilizing the vibration of the light reflection sensor detection target, which is the main point of the present invention, will be described below.
First, “regulating the traveling direction of the intermediate transfer belt 8”, which is a function of the suspension roller 12, will be described. As shown in FIG. 12, the intermediate transfer belt 8 is wound around the suspension roller 12 by a distance of the nip 701. While the intermediate transfer belt 8 is in the range of the nip 701, the suspension roller 12 always regulates the traveling direction of the intermediate transfer belt 8 in the tangential direction of the suspension roller 12. It continues until it passes the part 702. Since the regulating force does not work after the nip range end portion 702, the intermediate transfer belt advances in a tangential direction with respect to the nip range end portion 702, and the intermediate transfer belt is easily bent as it is separated from the suspension roller 12, and vibration in the vertical direction is generated. It gets bigger.

  Next, functions of the support member 501 will be described. The support member 501 lacks the function of “restricting the traveling direction of the intermediate transfer belt 8” that the suspension roller 12 has. This is because, as shown in FIG. 13, the support member 501 is only lightly pressed against the intermediate transfer belt 8 (the intermediate transfer belt 8 is not wound like the suspension roller 12), and the nip 711 is very narrow and the intermediate This is because the distance for regulating the traveling direction of the transfer belt 8 is too short. Therefore, even if the intermediate transfer belt 8 advances to the position of the nip range end portion 712, the direction of travel is hardly restricted. Therefore, the intermediate transfer belt 8 advances at a shallower angle than the tangent to the nip range end portion 712 while maintaining inertia. This continues for a distance 714 until there is no inertia. The distance 714 until the inertia disappears is a range in which the intermediate transfer belt 8 is not subject to regulation from either the suspension roller 12 or the support member 501, and thus vibrations in the vertical direction are unlikely to occur. Therefore, the support member 501 has a function of “creating a range 714 in which vertical vibration hardly occurs after the end of the nip range”, which the suspension roller 12 does not have.

The present invention is based on the function of the support member 501, and specific examples will be described.
As shown in FIG. 11, the output when the cylindrical support member 501 is arranged downstream of the suspension roller 12 and the detection position level of the light reflection sensor 40 is swung (arranged at D, E, F) is shown in FIG. Shown in The cylindrical support member 501 used in this example has a diameter of 8.0 mm. The support member 501 is arranged such that the vertex of the support member 501 is 12.0 mm in horizontal distance and 1.5 mm in height with respect to the vertex position of the suspension roller 12. The height of 1.5 mm causes the support member 501 to slightly bite into the intermediate transfer belt 8, and the angle 713 formed by the intermediate transfer belt 8 before and after the support member 501 is 7.1 degrees. This is because a range 714 in which vertical vibration is unlikely to occur is generated.

  The graph of FIG. 14 shows the output of the light reflection sensor 40 when the detection positions of the light reflection sensor 40 are points D, E, and F with respect to the arrangement position of the support member 501 that can be rotated by the stress of the intermediate transfer belt. .

  In the case of detection at point D, as in the case of detection at point B, belt vibration occurs when the seam 402 of the detent guide passes through the suspension roller, and the output of the light reflection sensor 40 is output every belt cycle. A sharp peak appears.

  When detecting at the point E, unless the parallelism of the support member 501 is adjusted with considerably high accuracy, it is affected by the knitting center of the support member 501, and the output of the light reflection sensor 40 varies with the rotation period of the support member 501. End up.

  When the detection is performed at the point F, the support member 501 can absorb the vibration generated when the detent guide joint 402 passes through the suspension roller 12 as well as “the vibration in the vertical direction hardly occurs after the end of the nip range”. effective. As a result, it is possible to obtain a stable output of the light reflection sensor 40 at all times.

  Therefore, in the present embodiment, the point F is defined as a position within the range 714 in which “the vibration in the vertical direction hardly occurs after the end of the nip range” and not affected by the knitting center of the support member 501. The position was 1.5 mm downstream from the top of the support member 501. In addition, if the detection position of the light reflection sensor 40 is within a range of 0.5 to 10 mm downstream from the end of the contact range of the support member 501 and the intermediate transfer belt 8 in the belt rotation direction, stable detection is performed. Can do.

  Further, with respect to the arrangement position of the support member 501 in the vertical direction, the support member is slightly bitten into the belt so that the angle formed by the intermediate transfer belt 8 before and after the support member is 1 to 14 degrees. did. As a result, it is possible to “create a range in which vibration in the vertical direction hardly occurs after the end of the nip range”. In the example, it is 7.1 degrees.

  In addition to this, as shown in FIG. 15, as a method for absorbing belt vibration, a cylindrical rectangular shape (small-diameter portion is formed by cutting a portion not corresponding to the light reflection sensors 40F, C, and R of the cylindrical support member 501 by 0.5 mm. When the supporting member 502 having the shape (having a shape) is used, the output of the light reflection sensor 40 is further stabilized. This is because the vibration of the intermediate transfer belt 8 is concentrated on the shaved groove portion, and the vibration of the light reflection sensor 40F, C, R detection position is reduced. The small diameter portion may be thinner by about 0.1 to 1 mm than the sensor corresponding portion.

Further, in order to eliminate the influence of the knitting center of the support members 501 and 502 and widen the range of the point F (sensor arrangement position), the support members 501 and 502 may be fixed.
Further, when the light reflection sensor 40 has a characteristic sensitive to the mounting tilt angle, the mounting is performed in accordance with the inclination of the intermediate transfer belt 8 in the range 714 that “the vibration in the vertical direction hardly occurs after the end of the nip range”. Tilt the angle. The degree of inclination may be 0.5 to 4.0 degrees. The mounting angle of the light reflection sensor 40 in this embodiment is tilted by 2.0 degrees.

  As described above, in the printer 100 of the present embodiment, the light reflection sensor 40 detects the intermediate transfer belt 8 as a belt body stably. As a result, the toner adhesion amount of the patch pattern (reference pattern) carried on the intermediate transfer belt 8 can be accurately detected, and excellent image quality can be obtained by appropriately controlling the image forming conditions.

As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this.
In the above-described embodiment, an example in which only one support member (501 or 502) is disposed has been described. However, one or more support members are disposed further downstream, and the upper and lower sides of the intermediate transfer belt 8 generated downstream of the light reflection sensor detection position are arranged. Directional vibration may be suppressed.

  Further, although the image forming apparatus using the intermediate transfer belt 8 as an example of the belt body has been described, it is needless to say that the present invention can be applied to a photosensitive belt and a conveyance belt which are other examples of the belt body.

  The image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions. The configuration of each unit such as an image forming unit and an exposure unit of the image forming apparatus can be changed as appropriate. The present invention can be applied not only to a full-color apparatus but also to a monochrome apparatus or a multi-color apparatus.

1 is a cross-sectional view illustrating a schematic configuration of a printer that is an example of an embodiment of an image forming apparatus to which the present invention is applied. It is an enlarged view showing one of the process cartridges in detail. FIG. 2 is a block diagram illustrating a part of an electric circuit of the printer in FIG. 1. It is a schematic diagram which shows a reference | standard pattern image. It is a schematic diagram which shows the installation pitch of a photoconductor drum. It is a schematic diagram showing a patch pattern formed on an intermediate transfer belt. It is a schematic diagram showing an intermediate transfer unit before reflecting the present invention. It is a graph which shows the output of the light reflection sensor in the intermediate transfer unit. FIG. 4 is a belt rear view showing a detent guide for an intermediate transfer belt. It is the side view. It is a schematic diagram which shows the intermediate transfer unit which provided the supporting member and the light reflection sensor according to this invention. It is a schematic diagram for demonstrating the function of the roller which suspends a belt. It is a schematic diagram for demonstrating the function of a supporting member. It is a graph which shows the sensor output by the arrangement position of the light reflection sensor shown in FIG. It is a perspective view which shows the structural example of a supporting member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 5 Developing apparatus 6 Process cartridge 7 Exposure apparatus 8 Intermediate transfer belt 9 Primary transfer bias roller 12 Transfer backup roller 15 Intermediate transfer unit 19 Secondary transfer roller 40 Reflective photo sensor 100 Printer 101 Reference image 150 Control part P Reference Pattern statue

Claims (9)

In an image forming apparatus having a belt body that is rotated by being suspended by at least two suspension rollers of a driving roller and a driven roller, and a light reflection sensor that detects the belt body.
A support member for supporting the belt body is provided between the two suspension rollers, and the light reflection is performed at a position of 0.5 to 10 mm downstream from the end of the contact range of the support member and the belt body in the belt rotation direction. An image forming apparatus for detecting a sensor. The support member according to claim 1, wherein the support member is slightly bitten into the belt body so that an angle formed by the belt body before and after the support member is 1 to 14 degrees. Image forming apparatus. The image forming apparatus according to claim 1, wherein the support member has a cylindrical shape. The said support member has a small diameter part which the diameter of the part which does not respond | correspond from the diameter of the part corresponding to the detection of the said light reflection sensor in an axial direction became thin about 0.1-1 mm, It is characterized by the above-mentioned. The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, wherein the support member is rotatable. The image forming apparatus according to claim 1, wherein the support member is fixed. 2. The image forming apparatus according to claim 1, wherein the light reflection sensor is inclined and arranged in accordance with an inclination of the belt body in a portion where the light reflection sensor is detected. 3. The image forming apparatus according to claim 1, wherein a second support member is provided downstream of a position where the light reflection sensor performs detection. The image forming apparatus according to claim 1, wherein a reference pattern formed on the belt body is detected by the light reflection sensor, and image forming conditions are controlled based on the detection result.

Images