JP5170336B2 - Toner adhesion amount measuring apparatus, image forming apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to a toner adhesion amount measuring apparatus, an image forming apparatus, and an image forming apparatus, and more particularly, a toner adhesion amount measuring apparatus for detecting the amount of toner attached to an image carrier having a curved surface, and an image forming apparatus using the same. And an image forming apparatus.

  In image forming apparatuses such as printers, FAX machines, and copiers based on electrophotographic processes, the amount of toner attached to a toner image formed on an image carrier such as a photosensitive member or an intermediate transfer member is measured for the purpose of improving image quality, and the measurement is performed. The image forming process parameters may be adjusted as needed based on the values.

  Specifically, a toner patch (reference pattern) for density detection is created on the surface of the image carrier, and the density of the reference pattern is detected by an optical sensor. In such an image forming apparatus, image density control is performed in which the developing potential is adjusted by changing the writing light intensity for forming a latent image, the charging bias, the developing bias, and the like based on the detection result of the toner density by the optical sensor. I am doing so.

  As such an optical sensor, a reflection type optical sensor provided with a light emitting means and a light receiving means is generally used. Various measures have been taken to improve the measurement accuracy of the toner density.

  In Patent Document 1, in order to compensate for the influence of a decrease in the amount of light by providing means for adjusting the amount of light emission based on the amount of diffuse reflected light in order to accurately measure the toner adhesion amount, a plurality of image patches are formed, On the other hand, by irradiating light from the light emitting element, detecting the regular reflection light quantity and diffuse reflection light quantity of the reflected light, and changing the light emission quantity of the light emitting element for each image patch in a predetermined case, thereby detecting the regular reflection light quantity An image forming apparatus is described that performs adjustment to keep the signal level of the diffuse reflection light amount by detecting the regular reflection light amount signal and the diffuse reflection light amount within a predetermined range.

  Further, in Patent Document 2, in order to always read the toner image on the belt body with high accuracy and to facilitate positioning of the image reading sensor, the image reading sensor is attached to the intermediate transfer belt between the driving roller and the driven roller. The support frame is provided with a receiving portion for supporting the shaft body at at least two points, and the image reading sensor is fixed and supported on the support frame at a position facing a line connecting these two points. The shaft body is rotated between the driving roller and the driven roller so that the peripheral surface of the shaft body is in contact with the intermediate transfer belt and presses the intermediate transfer belt in the direction of the image reading sensor. An image forming apparatus is described in which a shaft body is supported by a receiving portion when the intermediate transfer unit is attached to the apparatus housing.

  By the way, in order to reduce the size of the image forming apparatus, each part constituting the image forming apparatus is downsized. For example, a so-called endless belt may be used as a transfer belt as an image carrier that is a detection target of the reflection type optical sensor for measuring the toner adhesion amount described above.

  In order to improve the accuracy of image formation on the transfer belt, a developing unit or the like may be installed on the flat surface. In such a case, the reflection type optical sensor detects the size of the image forming apparatus. It is desirable that the target surface is a curved surface portion located on the side of the transfer belt.

  However, when the reflected light is detected at the curved surface portion of the image carrier, the distance between the reflective optical sensor and the detection symmetry surface, the facing angle, and the like may deviate from the design conditions of the reflective optical sensor. In such a case, the amount of received light of the specularly reflected light is significantly reduced corresponding to the curvature of the surface to be detected, making accurate measurement difficult. Such an accurate measurement becomes difficult especially when the glossiness of the surface to be detected is low.

  The present invention has been made in view of the above problems, and when measuring the toner adhesion amount of an image carrier with a reflective optical sensor, the toner amount can be easily and accurately measured even if the measurement is performed on the curved surface of the image carrier. An object of the present invention is to provide a toner adhesion amount measuring device, an image forming device, and an image forming device capable of stably measuring.

The invention of claim 1 includes an image bearing member on which a toner image is formed, an intermediate transfer belt to which the toner image on the image bearing member is transferred along with the passed around a plurality of rollers, of the plurality of rollers It provided opposite to the first curved surface portion of the intermediate transfer belt is wound around a portion in one of the rollers, the reflection type optical sensor for detecting the toner over amount of the first curved surface portion of the intermediate transfer belt A pair of second curved surfaces having a center of curvature at the center of rotation of the one roller, and a pair of contacts with the second curved surfaces at positions separated from each other in the circumferential direction of the second curved surface. In the state where the third curved surface portion is in contact with the second curved surface portion and the pair of third curved surface portions are in contact with each other, the reflective optical sensor is disposed at a position spaced apart from the first curved surface portion. holding, and the holding member,
An image forming apparatus comprising:

According to a fifth aspect of the present invention, there is provided an image carrier on which a toner image is formed, an intermediate transfer belt on which the toner image on the image carrier is transferred while being stretched over a plurality of rollers, A reflective optical sensor provided opposite to the first curved surface portion of the intermediate transfer belt, which is a portion wound around one roller, and detecting the toner amount of the first curved surface portion of the intermediate transfer belt ; A second curved surface portion having the center of curvature of the one roller as a center of curvature, and an arc portion that is separably attached to the second curved surface portion, and the arc portion on the second curved surface portion. in the state in which is mounted, for holding the reflective optical sensor at a position at a distance from said first curved surface portion, an image forming apparatus according to claim Rukoto comprises a holding member.

  According to the toner adhesion amount measuring apparatus, the image forming apparatus, and the image forming apparatus according to the present invention, since the reflective optical sensor can always measure in a state of facing the center of curvature of the curved surface portion of the image carrier, It is possible to adapt the distance, facing angle, etc. to the curved surface, which is the target surface, to the design conditions of the reflective optical sensor, to measure the toner adhesion amount with high accuracy, and to achieve high accuracy image density in the image forming apparatus. Control becomes possible.

1 is a longitudinal sectional view showing a main part of a color printer according to an embodiment. 1A and 1B show a configuration of a toner adhesion amount measuring apparatus according to a first embodiment, in which FIG. 1A is a perspective view and FIG. FIG. 3 is a side view showing the movement of the toner adhesion amount measuring device shown in FIG. 2. It is a figure which shows the reflection state of the light inject | emitted from a reflection type optical sensor, (a) is a schematic diagram which shows embodiment, (b) is a schematic diagram which shows comparison. FIG. 6 is a schematic diagram illustrating another operation of the toner adhesion amount measuring apparatus illustrated in FIG. 2. FIG. 6 is a schematic diagram illustrating a modification of the first embodiment. 2 shows a configuration of a toner adhesion amount measuring apparatus according to a second embodiment, where (a) is a perspective view and (b) is a side view. FIG. FIG. 10 is a side view illustrating a configuration of a toner adhesion amount measuring apparatus according to a third embodiment. It is a side view for demonstrating a tilt amount. It is a graph which shows the relationship between the tilt angle of a sensor, and a sensor output. It is a side view which shows the structure of the toner adhesion amount measuring apparatus which concerns on 4th Embodiment. It is a side view which shows the structure of the toner adhesion amount measuring apparatus which concerns on the modification of 4th Embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a main part of a color printer to which an electrophotographic process is applied as an embodiment of an image forming apparatus according to the present invention. The color printer 1 includes an image forming unit 14a as an image forming apparatus including a paper feed cassette 2 for supplying paper as an image recording medium, developing units 3a, 3b, 3c, and 3d and photoconductors 4a, 4b, 4c, and 4d. , 14b, 14c, 14d, and an intermediate transfer belt 13 as an image carrier.

  On the photoreceptors 4a, 4b, 4c, and 4d, an electrostatic latent image is formed by laser light having image information emitted in response to laser drive input from a laser drive device (not shown). The developing units 3a, 3b, 3c, and 3d develop the electrostatic latent images formed on the photoreceptors 4a, 4b, 4c, and 4d with toners of predetermined color elements (cyan, magenta, yellow, and black), respectively. .

  The intermediate transfer belt 13 is arranged so as to be stretched over the driving roller 7 and the tension roller 6, and the toner images of the respective color elements are superimposed on the photoreceptors 4a, 4b, 4c, and 4d on which the toner images of the respective colors are formed. Transcribed. Further, a secondary transfer roller 11 is pressed against the driving roller 7 via an intermediate transfer belt 13, and a toner image is transferred to a sheet conveyed between the driving roller 7 and the secondary transfer roller 11. . A cleaning device 8 is disposed on the intermediate transfer belt 13 to remove residual toner on the intermediate transfer belt 13.

  The color printer 1 also includes a conveyance path 9 that conveys the paper supplied from the paper feed cassette 2 via the intermediate transfer belt 13, a paper feed roller 12 that supplies the paper from the paper feed cassette 2 to the conveyance path 9, and an intermediate transfer. A fixing unit 10 that performs heating and pressurization is provided to fix the image on the sheet on which the color image is transferred from the belt 13.

  In this example, a toner adhesion amount measuring device 5 for measuring the toner adhesion amount in the toner image on the intermediate transfer belt 13 is provided.

  In the color printer 1 having such a configuration, the toner adhesion amount on the photosensitive member or the transfer belt with respect to a predetermined laser driving input is not always strictly constant, but varies depending on the environment, deterioration with time, and the like. For this reason, in order to obtain a fixed adhesion amount, it is necessary to appropriately adjust and control parameters such as a developing bias, and a reflective optical sensor is used to detect the toner adhesion amount. In this example, the reflective optical sensor includes two light receiving elements, a light emitting element that emits detection light, a light receiving element that receives specularly reflected light, and a light receiving element that receives diffusely reflected light.

  The toner adhesion amount measuring device will be described below. 2A and 2B show the configuration of the toner adhesion amount measuring apparatus according to the first embodiment. FIG. 2A is a perspective view, FIG. 2B is a side view, and FIG. 3 shows the toner adhesion amount measuring apparatus shown in FIG. FIG. 4 is a diagram showing a reflection state of light emitted from a reflective optical sensor, (a) is a schematic diagram showing an embodiment, and (b) is a schematic diagram showing a comparison. FIG. 5 is a schematic diagram showing another operation of the toner adhesion amount measuring apparatus shown in FIG.

  The toner adhesion amount measuring device 20 according to the present example has a configuration in which the reflective optical sensor 21 is held by a holding member 25. Thus, the toner amount of the curved surface portion 13a that is a portion wound around the tension roller 6 in the surface of the intermediate transfer belt 13 that is the image carrier is measured.

  The holding member 25 includes two arm portions 22 and 22 that are rotatably supported at one end by the shaft 6a of the tension roller 6 and a beam portion 23 that is stretched between the other ends of the arm portions 22 and 22. It consists of. The reflective optical sensor 21 is arranged at the approximate center of the beam portion 23, and the measurement surface thereof is arranged toward the axis 6a. With this structure, as shown in FIG. 3, the holding member 25 can be rotated around the shaft 6a of the tension roller 6, and the reflective optical sensor 21 is connected to the curved surface portion 13a of the intermediate transfer belt 13, the curved surface. Is kept in a state where it is always faced to the central axis, and is maintained at a certain distance from the predetermined intermediate transfer belt 13.

  According to the toner adhesion amount measuring apparatus 20 according to the present example, as shown in FIG. 4A, the light emitted from the light emitting element of the reflective optical sensor 21 is emitted toward the shaft 6a of the tension roller 6 and is intermediate. The light enters the curved surface portion 13a of the transfer belt 13 perpendicularly and is reflected. For this reason, in the toner adhesion amount measuring apparatus 20 according to this example, the reflected light of the intermediate transfer belt 13 can be efficiently received by the light receiving element of the reflective optical sensor 21. On the other hand, as shown in FIG. 4B, the light emitted in the direction deviated from the axis 6a does not enter the surface of the intermediate transfer belt 13 perpendicularly, and the reflected light is reflected from the reflective optical sensor 21. It will be injected in the direction away from.

  Further, according to the toner adhesion amount measuring apparatus 20 according to the present example, the risk of the connection of the harness (wire bundle) or the connector connected to the reflective optical sensor 21 being poor is reduced, and the reliability is improved. Can do. That is, as shown in FIG. 5, when the tension roller 6 moves according to the tension of the intermediate transfer belt 13, the arm portions 22 and 22 by the tension roller 6 also vibrate. In this example, the vibration transmitted to the reflective optical sensor 21 can be absorbed by the movement of the arm portion 22 and the vibration of the reflective optical sensor 21 can be reduced. In the figure, reference numeral 15 denotes a coil spring that urges the tension roller 6.

  Therefore, according to this example, the reflective optical sensor is always positioned in a state of facing the center of curvature of the curved surface portion so that the distance to the detection target surface, the facing angle, etc. do not deviate from the design conditions of the reflective optical sensor. Therefore, the light amount can be detected with high accuracy, and the image density of the image forming apparatus can be controlled with high accuracy.

  FIG. 6 is a schematic diagram illustrating a toner adhesion amount measuring apparatus according to a modification of the first embodiment. In the toner adhesion amount measuring apparatus 70 according to this example, the arm portion 72 that supports the reflective optical sensor 71 includes a base portion 72a that supports the beam portion 73 and a bifurcated portion that is formed in a direction in which the tension roller 6 is sandwiched from the base portion 72a. 72b and 72b. A beam portion 73 is disposed on the base portion 72a, and planetary disks 74 and 74 that rotate in contact with the disk portion 16 disposed on the outer periphery of the tension roller 6 are disposed at the tips of the bifurcated portions 72b and 72b. For this reason, also in 70 according to this example, the reflective optical sensor 71 is always located in a state of facing the center of curvature of the curved surface portion of the tension roller 6, and the distance to the detection target surface, the facing angle, etc. are reflective. It is held so as not to deviate from the design conditions of the optical sensor. For this reason, it is possible to detect the amount of light with high accuracy and to control the image density of the image forming apparatus with high accuracy.

  Next, the toner adhesion amount measuring device 30 according to the second embodiment will be described. 7A and 7B show the configuration of the toner adhesion amount measuring apparatus according to the second embodiment, wherein FIG. 7A is a perspective view and FIG. 7B is a side view.

  The toner adhesion amount measuring device 30 according to this example includes a configuration in which the reflective optical sensor 31 is held by a holding member 35 including a distance adjusting mechanism 34. Thus, the measurement surface of the reflective optical sensor 31 is always directed to the axis 6a, and the distance between the reflective optical sensor 31 and the curved surface portion 13a can be adjusted.

  The holding member 35 includes two arm portions 32 and 32 rotatably supported at one end on the shaft 6a of the tension roller 6, and a beam portion 33 spanned between the other ends of the arm portions 32 and 32. The distance adjusting mechanism 34 is disposed at the attachment portion between the beam portion 33 and the arm portion 22. The distance adjustment mechanism 34 is configured by combining an elastic body such as a spring 34a and an adjustment member such as a screw 34b. By rotating the screw 34b, the curved surface portion 13a that is a detection surface, the reflective optical sensor 31, and the like. The position in the distance direction can be adjusted.

  In general, a reflective optical sensor is composed of light emitting elements such as LEDs and laser diodes, and light receiving elements such as phototransistors and photodiodes. The irradiation angle and light receiving angle are determined according to the distance from the object to be measured. Designed. For this reason, the measurement accuracy decreases under conditions that deviate from the designed distance characteristics.

  For this reason, in this example, the distance adjustment mechanism 34 is configured by combining an elastic body such as a spring 34 a and an adjustment member such as a screw 34 b, and the distance between the curved surface portion 13 a that is a detected surface and the reflective optical sensor 31. The position of the direction can be adjusted.

  Therefore, according to the present embodiment, the distance between the curved surface portion and the reflective optical sensor can be adjusted in accordance with the distance characteristics of the reflective optical sensor, and the reflective optical sensor can be used without reducing the light amount detection accuracy. Therefore, it is possible to control the image density of the image forming apparatus with high accuracy.

  Next, a toner adhesion amount measuring apparatus 40 according to the third embodiment will be described. FIG. 8 is a side view showing the configuration of the toner adhesion amount measuring apparatus according to the third embodiment, FIG. 9 is a side view for explaining the tilt amount, and FIG. 10 is a graph showing the relationship between the tilt angle of the sensor and the sensor output. It is. As shown in FIG. 8, the toner adhesion amount measuring apparatus 40 according to this example has a reflective optical sensor 41 attached to a holding member 45 via an angle adjustment mechanism 44. With such a configuration, the tilt angle of the reflective optical sensor 41 with respect to the curved surface portion 13a that is the detection surface (the inclination of the reflection optical sensor with respect to the detection surface: see FIG. 9) can be adjusted.

  In this example, the angle adjusting mechanism 44 is provided with a male screw 44a, and the tilt angle of the reflective optical sensor 41 is changed by rotating the male screw 44a.

  As described above, the reflective optical sensor 41 is composed of a light emitting element and a light receiving element, and has a feature of high directivity. The reflective optical sensor 41 has unique characteristics for each element in the direction in which the detection light of the sensor is emitted. If the reflective optical sensor 41 is attached to the holding member 45 as it is, depending on the reflective optical sensor 41, the emission direction of the detection light may not be accurately directed to the axis 6a, and the detection efficiency may be lowered. That is, as shown in FIG. 10, the sensor output becomes maximum when the tilt angle is 0, and the output decreases as the tilt angle increases. For this reason, in this example, the tilt angle of the reflective optical sensor 41 can be adjusted so that the output is maximized, and the measurement accuracy of the toner adhesion amount is improved.

  Therefore, according to the present embodiment, it is possible to correct individual directivity of the optical sensor and stabilize the accuracy of toner adhesion amount measurement.

  Next, a toner adhesion amount measuring apparatus 50 according to the fourth embodiment will be described. FIG. 11 is a side view showing the configuration of the toner adhesion amount measuring apparatus according to the third embodiment. In this example, a holding portion 54 is formed on the arm portion 52 constituting the holding member 55, and the beam portion 53 to which the reflective optical sensor 51 is attached is detachably held.

  According to this example, the reflective optical sensor 51 can be easily attached to and detached from the holding member 55 when cleaning the dirt attached to the light receiving and emitting unit of the reflective optical sensor 51 or replacing the reflective optical sensor 51. Can be improved.

In this example, the convex part 54a is arranged above the holding part 54, and the concave part 53a is arranged above the beam part 53 so as to be asymmetric in the vertical and horizontal directions. For this reason, according to this example, the reflective optical sensor 51 can be disposed in the position and orientation determined by the holding member 55, and the reflective optical sensor 51 can be easily positioned. Mismounting can be prevented.
In this example, the beam portion 53 can be attached to and detached from the arm portion 52. However, the reflective optical sensor 51 can be attached to and detached from the beam portion 53 fixed to the arm portion 52. .

  Next, a modification of the fourth embodiment will be described. FIG. 12 is a side view showing a configuration of a toner adhesion amount measuring apparatus according to a modification of the fourth embodiment. The toner adhesion amount measuring device 60 according to this example is structured to be separable from the shaft 6 a of the tension roller 6 of the arm portion 62 constituting the holding member 65. The reflective optical sensor 51 is fixed to a beam unit 53 fixed to the tip of the arm unit 62. According to this example, the holding member 65 can be separated from the tension roller 6, and the assemblability and maintenance of the unit to which the intermediate transfer belt 13 is attached can be improved.

  In each of the above examples, the intermediate transfer belt is used as the image carrier. However, the image carrier may be a cylindrical one like a photoconductor.

  As described above, according to the present invention, the reflective optical sensor is always located in a state of facing the center of curvature so that the distance from the detection target surface, the facing angle, and the like do not deviate from the reflective optical sensor design conditions. By being held, the light amount can be detected with high accuracy. This also enables highly accurate image density control in the image forming apparatus.

  Further, by making the reflection type optical sensor holding means rotatable, it is possible to avoid the reflection type optical sensor when removing a paper jam even when the transfer paper conveyance path is arranged in the vicinity. . In the endless belt, the tension roller moves due to the load applied to the belt. Even if the reflective optical sensor detects the curved surface portion of the tension roller, the distance and the tilt angle are accurately maintained. It becomes possible.

In addition, according to the present invention, by having the distance adjusting means with respect to the detected surface, it is possible to match the distance characteristics of the reflective optical sensor and to arrange without reducing the light amount detection accuracy.
As a result, the image forming apparatus can control the image density with high accuracy.

  In addition, according to the present invention, if the holding means itself is a detachable structure, assembly can be facilitated and parts can be easily replaced. Further, in an image forming apparatus such as a copying machine or a printer, it may be close to a transfer paper conveyance path, and when a paper jam or the like occurs, the reflection optical sensor holding means can be easily removed. It is convenient.

  Further, according to the present invention, by making the optical sensor detachable, it is possible to expect easy assembly and improved exchangeability of the reflective optical sensor. In an image forming apparatus such as a copying machine or a printer, it is conceivable that the image forming apparatus is close to a transfer paper conveyance path, and it is convenient that the reflective optical sensor can be easily removed when a paper jam or the like occurs.

  In addition, according to the present invention, it is possible to absorb the variation in directivity of the reflection type optical sensor by adjusting the tilt angle of the reflection type optical sensor (the inclination of the optical sensor with respect to the detected surface). Arrangement is possible without reducing accuracy. As a result, the image forming apparatus can control the image density with high accuracy.

  In this way, in a reflective optical sensor that requires delicate dimensional control of the distance and tilt angle with respect to the detected surface, even if the detected surface is a curved surface, the distance and facing angle can be designed. It becomes easy to manage within the conditions, and as a result, accurate light quantity measurement is possible. As a result, highly accurate image density control is possible, and an image forming apparatus with high image quality can be realized.

DESCRIPTION OF SYMBOLS 1 Color printer 2 Paper feed cassette 3a, 3b, 3c, 3d Developing unit 4a, 4b, 4c, 4d Photoconductor 5 Toner adhesion amount measuring device 6 Tension roller 6a Shaft 7 Driving roller 8 Cleaning device 9 Conveying path 10 Fixing unit 11 2 Next transfer roller 12 Paper feed roller 13 Intermediate transfer belt 13a Curved portions 14a, 14b, 14c, 14d Image forming unit 15 Coil spring 16 Disk unit 20 Toner adhesion amount measuring device 21 Reflective optical sensor 22 Arm unit 22
23 Beam unit 25 Holding member 30 Toner adhesion amount measuring device 31 Reflective optical sensor 32 Arm unit 32,
33 Beam portion 34 Distance adjustment mechanism 34a Spring 34b Screw 35 Holding member 40 Toner adhesion amount measuring device 41 Reflective optical sensor 44 Angle adjustment mechanism 44a Male screw 45 Holding member 50 Toner adhesion amount measuring device 51 Reflective optical sensor 52 Arm portion 53 Beam part 53a Concave part 54 Holding part 54a Convex part 55 Holding member 60 Toner adhesion amount measuring device 62 Arm part 65 Holding member 70 Toner adhesion amount measuring device 71 Reflective optical sensor 72 Arm part 72a Base parts 72b and 72b Bifurcated part 73 Beam part 74 , 74 Planetary disk 21 Reflective optical sensor 31 Reflective optical sensor 41 Reflective optical sensor 51 Reflective optical sensor 71 Reflective optical sensor 23 Beam part 33 Beam part 53 Beam part 73 Beam part

JP 2007-93761 A JP 2004-326085 A

Claims (10)

An image carrier on which a toner image is formed,
An intermediate transfer belt that is stretched over a plurality of rollers and onto which a toner image on the image carrier is transferred ;
One of the a wound around a portion of the roller provided opposite to the first curved surface portion of the intermediate transfer belt, toner over amount of the first curved surface portion of the intermediate transfer belt of the plurality of rollers A reflective optical sensor for detecting
A second curved surface portion having the center of curvature at the center of rotation of the one roller;
The second curved surface portion has a pair of third curved surface portions that respectively contact the second curved surface portion at positions separated from each other in the circumferential direction, and the pair of first curved surfaces on the second curved surface portion. in the state where third curved surface portion is in contact, holds the reflective optical sensor at a position at a distance from said first curved surface portion, and the holding member,
An image forming apparatus comprising: In a state where the pair of third curved surface portions are in contact with the second curved surface portion, the holding member holds the reflective optical sensor at a position spaced horizontally from the first curved surface portion. you,
The image forming apparatus according to claim 1, characterized in that. The third curved portion you rotate in contact with the second curved portion minutes,
The image forming apparatus according to claim 1 or 2, characterized in that. The second curved portion is Ru is disposed on the outer periphery of said one roller,
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. An image carrier on which a toner image is formed;
An intermediate transfer belt that is stretched over a plurality of rollers and onto which a toner image on the image carrier is transferred;
A portion of the plurality of rollers that is wound around one of the plurality of rollers is provided to face the first curved surface portion of the intermediate transfer belt, and the toner amount of the first curved surface portion of the intermediate transfer belt is determined. A reflective optical sensor to detect ;
A second curved surface portion having the center of curvature at the center of rotation of the one roller;
An arc portion that is separably attached to the second curved surface portion, and in a state where the arc portion is attached to the second curved surface portion, at a position spaced apart from the first curved surface portion; A holding member for holding the reflective optical sensor ;
An image forming apparatus comprising Rukoto equipped with. In a state in which the arcuate portion to the second curved surface portion is attached, the retaining member, that holds the reflective optical sensor at a position at a distance in a horizontal direction from said first curved surface portion,
The image forming apparatus according to claim 6 . The second curved surface portion is an axis of the one roller;
The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus. The one roller is a tension roller.
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. A plurality of the image carrier,
A toner image of each color is formed on each of the plurality of image carriers,
The toner images of each color on the plurality of image carriers are transferred to the intermediate transfer belt in a superimposed manner.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A secondary transfer roller pressed against the intermediate transfer belt;
The toner image transferred to the intermediate transfer belt is transferred to a sheet conveyed between the intermediate transfer belt and a secondary transfer roller.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.