JP2014145913A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents speed of an intermediate transfer body from being changed due to temperature change of the intermediate transfer body.SOLUTION: An image forming apparatus (100) includes: primary transfer means (503) for transferring a toner image formed on an image carrier to an intermediate transfer body (501); secondary transfer means (504, 506) for transferring the toner image transferred on the intermediate transfer body (501) to a transfer material; detection means (902) for detecting changes in speed of the intermediate transfer body (501); and temperature adjustment means (905) for adjusting temperature of the intermediate transfer body (501) so as to keep a constant speed.

Description

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

  In recent image forming apparatuses, a tandem type intermediate transfer belt system is adopted for colorization and strengthening of paper compatibility. Further, an elastic belt having an elastic layer may be employed as the intermediate transfer belt in order to cope with uneven paper and rippled paper (hereinafter, the intermediate transfer belt having such a configuration is referred to as an elastic intermediate transfer belt).

  The elastic modulus of the elastic layer of the elastic intermediate transfer belt fluctuates due to temperature fluctuation or deterioration with time. Specifically, the elastic modulus of the elastic layer increases (hardens) in a low temperature and low humidity environment, and conversely, the elastic modulus of the elastic layer decreases (softens) in a high temperature and high humidity environment. Also, the elastic modulus increases with time. As described above, when the elastic modulus changes, the nip shape of the primary transfer portion, the nip shape of the secondary transfer portion, and the recording paper entry posture change, and the direction perpendicular to the paper feed direction of banding, shock jitter, etc. Density unevenness may occur. The primary transfer portion is a portion that transfers a toner image formed on an image carrier such as a photosensitive drum to an elastic intermediate transfer belt. The secondary transfer portion is a portion that transfers the toner image transferred to the elastic intermediate transfer belt to a transfer material such as recording paper.

For this reason, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2001-154504), at least one coating layer is formed on the surface of an inner layer made of a rubber-like elastic body having a volume resistivity of 10 ⁴ to 10 ¹² Ω · cm. A transfer belt having a high-rigidity coating layer and having a tensile elastic modulus E as a whole transfer belt of E / E0 ≧ 2 is disclosed. E0 is the tensile modulus of the inner layer. As a result, the flexibility of the belt can be maintained and the elongation during driving can be suppressed.

  Japanese Patent Application Laid-Open No. 2005-250331 discloses an elastic intermediate transfer member having an elastic layer having a multilayer structure and a temperature gradient, an image forming unit for forming a toner image on the elastic intermediate transfer member, and an elastic member. An image forming apparatus having a means for transferring a toner image on an intermediate transfer member onto a recording material at a transfer portion is disclosed. Then, the elastic modulus of the elastic intermediate transfer member is controlled to be within a desired range. This makes it possible to reverse the shape change of the elastic intermediate transfer member.

  Japanese Patent Application Laid-Open No. 2010-210656 discloses a belt that is a drive source of a drive rotating body that detects a speed variation of the intermediate transfer belt and moves the intermediate transfer belt endlessly based on the detection result. An image forming apparatus that controls the drive speed of a drive source is disclosed. As a result, the conveyance speed of the intermediate transfer belt due to the fluctuation of the driving roller diameter does not occur, and a stable image with little color misregistration can be obtained.

  Japanese Patent Application Laid-Open No. 2006-10985 discloses an image forming apparatus configured to detect a temperature of a surface of a driving roller of an intermediate transfer belt and always keep the temperature constant. As a result, the conveyance speed of the intermediate transfer belt due to the fluctuation of the driving roller diameter does not occur, and a stable image with little color misregistration can be obtained.

  In the invention of Patent Document 1, a high-rigidity coating layer is formed on the surface of an inner layer made of a rubber-like elastic body, and the tensile elastic modulus E of the entire transfer belt is set to E / E0 ≧ 2, so that the flexibility of the belt This makes it possible to maintain the properties and suppress the elongation during driving. However, if the tensile elastic modulus of each layer fluctuates and the above condition E / E0 ≧ 2 cannot be satisfied, the flexibility of the belt and the nip ability of papers may not be maintained. Further, there is a risk that banding, shock jitter, and the like are deteriorated due to elongation due to driving.

  Further, the invention of Patent Document 2 detects the electric resistance of the elastic intermediate transfer member or detects the shape deformation with an optical sensor, converts the elastic modulus into the predetermined elastic modulus. The temperature is adjusted using a temperature adjusting device so as to suppress it. However, the conversion accuracy when converting to the elastic modulus may deteriorate due to the installation environment conditions where the apparatus is placed, the contamination of the belt surface, local deformation, and scratches. In some cases, it is impossible to restore the shape deformation of the elastic intermediate transfer member by adjusting the value.

  Further, the invention of Patent Document 3 is mainly intended to suppress the occurrence of color misregistration due to the change in the diameter of the drive roller over time, and does not consider the temperature variation of the intermediate transfer belt. In addition, no consideration is given to the fact that the speed variation of the intermediate transfer belt occurs due to the change in the nip shape of the primary transfer portion or the nip shape of the secondary transfer portion.

  Further, the invention of Patent Document 4 is mainly intended to suppress the occurrence of color misregistration due to fluctuations in the driving roller diameter, and the intermediate nip shape of the primary transfer portion and the secondary transfer portion is changed by changing the nip shape. No consideration is given to the fact that the speed fluctuation of the transfer belt occurs.

  An object of the present disclosure is to provide an image forming apparatus capable of reducing the speed fluctuation of the intermediate transfer member due to the temperature change of the intermediate transfer member.

An image forming apparatus according to an aspect of the present disclosure includes:
A primary transfer means for transferring a toner image formed on the image carrier to an intermediate transfer member;
Secondary transfer means for transferring the toner image transferred to the intermediate transfer member to a transfer material;
Detecting means for detecting a speed fluctuation of the intermediate transfer member;
Temperature adjusting means for adjusting the temperature of the intermediate transfer member so that the speed fluctuation is constant;
It is characterized by having.

  According to one aspect of the present disclosure, it is possible to reduce the speed fluctuation of the intermediate transfer member due to the temperature change of the intermediate transfer member.

1 is a diagram illustrating a configuration example of an image forming apparatus 100. FIG. 3 is a diagram illustrating a configuration example of an image forming process unit 200. FIG. 3 is a diagram illustrating a configuration example of an intermediate transfer belt 501. FIG. FIG. 6 is a diagram illustrating a configuration example for reading a scale 900 provided on an intermediate transfer belt 501. FIG. 4 is a diagram illustrating an example of a control configuration for rotating and moving an intermediate transfer belt. FIG. 6 is a diagram illustrating an example of a processing operation for rotational movement control of the intermediate transfer belt 501 before starting printing. FIG. 10 is a diagram illustrating an example of processing operation for rotational movement control of the intermediate transfer belt 501 during printing. It is a figure which shows the relationship between belt temperature and belt speed deviation. It is a figure which shows the relationship between belt temperature and a banding evaluation value. It is a figure which shows the example of a relationship between paper type, paper paper thickness, and a correction value. FIG. 4 is a diagram illustrating an example of a control configuration for rotating and moving an intermediate transfer belt. FIG. 6 is a diagram illustrating an example of a processing operation for rotational movement control of the intermediate transfer belt 501 before starting printing. It is a figure which shows the relationship between belt temperature and a drive motor torque deviation. FIG. 6 is a diagram illustrating an example of a processing operation for rotational movement control of the intermediate transfer belt 501 before starting printing.

(Outline of Embodiment of Image Forming Apparatus 100 According to One Aspect of Present Disclosure)
First, an overview of an image forming apparatus 100 according to an aspect of the present disclosure will be described with reference to FIGS. 1 and 2. 1 and 2 illustrate a schematic configuration example of an image forming apparatus 100 according to an aspect of the present disclosure.

  An image forming apparatus 100 according to an aspect of the present disclosure includes a primary transfer unit, a secondary transfer unit, a detection unit, and a temperature adjustment unit.

  The primary transfer unit transfers the toner image formed on the image carrier 2011 to the intermediate transfer member 501. As the image carrier 2011, the photosensitive drum 2011 of the image forming process unit 200 functions. The intermediate transfer member 501 functions as the intermediate transfer belt 501 of the intermediate transfer unit 500. The primary transfer unit functions with the primary transfer roller 503 and the photosensitive drum 2011.

  The secondary transfer unit transfers the toner image transferred to the intermediate transfer member 501 to the transfer target material. A recording paper or the like functions as the transfer material. The secondary transfer unit functions with the belt driving roller 504 and the secondary transfer roller 506.

  The detection unit detects a speed variation of the intermediate transfer member 501. The mark sensor 902 functions as the detection means. The temperature adjustment unit adjusts the temperature of the intermediate transfer member 501 so that the speed fluctuation of the intermediate transfer member 501 detected by the detection unit 902 is constant. As the temperature adjusting means, the control unit 903 and the heater 905 function.

  The image forming apparatus 100 according to an aspect of the present disclosure adjusts the temperature of the intermediate transfer body 501 so that the speed fluctuation of the intermediate transfer body 501 detected by the detection unit 902 is constant. Thereby, the speed fluctuation of the intermediate transfer member due to the temperature change of the intermediate transfer member can be reduced. Hereinafter, the image forming apparatus 100 of the present embodiment will be described in detail with reference to the accompanying drawings.

<Configuration Example of Image Forming Apparatus 100>
First, a configuration example of the image forming apparatus 100 of the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus 100 according to the present embodiment. FIG. 2 is a diagram illustrating a configuration example of the image forming process unit 200 mounted on the image forming apparatus 100.

  The image forming apparatus 100 according to the present embodiment includes an image forming process unit 200 that is a toner image forming unit. The image forming apparatus 100 according to this embodiment includes four image forming process units 200 for yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Each image forming process unit 200 forms a toner image using Y, M, C, and K toners. Each image forming process unit 200 is configured as shown in FIG. Since each image forming process unit 200 is configured in the same manner, in this embodiment, one image forming process unit 200 will be described as an example.

  As shown in FIG. 2, the image forming process unit 200 includes a photoconductor unit 201, a developing unit 202, and a temperature sensor 203. The photoconductor unit 201 and the developing unit 202 can be attached to and detached from the image forming apparatus 100 main body. The temperature sensor 203 is a sensor for detecting the surface temperature of the photosensitive drum 2011.

  In the image forming process unit 200 of this embodiment, the photosensitive drum 2011 is charged by the photosensitive unit 201. Then, an electrostatic latent image is formed on the photosensitive drum 2011 by the laser light L emitted from the exposure unit 300 (see FIG. 1). Then, toner is attached to the electrostatic latent image formed on the photosensitive drum 2011 from the developing unit 202 to form a toner image on the photosensitive drum 2011. The photosensitive drum 2011 is in contact with the primary transfer roller 503 with the intermediate transfer belt 501 interposed therebetween, and the photosensitive drum 2011 and the primary transfer roller 503 form a primary transfer nip. The toner image formed on the photosensitive drum 2011 is transferred to the intermediate transfer belt 501 at the primary transfer nip.

  The photoreceptor unit 201 includes a photoreceptor drum 2011, a drum cleaning device 2012, a lubricant application brush 2013, a lubricant 2014, a lubricant application blade 2015, a charging roller 2016, a charging roller cleaner 2017, and the like.

  The photosensitive drum 2011 is a drum-shaped image carrier. Inside the photosensitive drum 2011, a halogen heater 2018 is provided. The halogen heater 2018 is for heating the photosensitive drum 2011.

  The drum cleaning device 2012 is a latent image carrier cleaning unit that removes and collects transfer residual toner and the like attached to the photosensitive drum 2011. The drum cleaning device 2012 includes a cleaning blade, a screw, and the like. The lubricant application brush 2013 and the lubricant 2014 apply the lubricant 2014 to the photosensitive drum 2011 so that the surface friction coefficient of the photosensitive drum 2011 becomes a predetermined value. As the lubricant 2014, zinc stearate or the like is used. The lubricant application blade 2015 uniformly applies the lubricant 2014 on the photosensitive drum 2011. The charging roller 2016 uniformly charges the photosensitive drum 2011. A charging roller cleaner 2017 is in contact with the charging roller 2016.

  The developing unit 202 includes a first developer accommodating portion 2022 in which a first conveying screw 2021 is disposed, and a second developer accommodating portion 2024 in which a second conveying screw 2023 is disposed. In addition, a toner concentration sensor 2025 including a magnetic permeability sensor is installed on the lower surface of the first developer accommodating unit 2022. The image forming apparatus 100 according to the present embodiment calculates a mixing ratio between carrier particles, which are magnetic materials, and toner based on the magnetic permeability detected by the toner concentration sensor 2025. Then, the toner is supplied from the toner bottle 800 (see FIG. 1) to the first developer accommodating portion 2022 of the developing unit 202 so that the toner concentration detected by the toner concentration sensor 2025 becomes a predetermined toner concentration. The first conveying screw 2021 is rotationally driven by a driving means (not shown), and supplies the developer in the first developer accommodating portion 2022 to the second developer accommodating portion 2024. The second conveying screw 2023 in the second developer accommodating portion 2024 is rotationally driven by a driving means (not shown), and conveys the developer to the developing sleeve 2026.

  Above the second conveying screw 2023, a developing sleeve 2026 is disposed in a posture parallel to the second conveying screw 2024. The developing sleeve 2026 is driven to rotate counterclockwise. The developing sleeve 2026 is made of a nonmagnetic material such as aluminum, and the surface is roughened by sandblasting. A magnet (not shown) is provided inside the developing sleeve 2026, and a part of the developer conveyed by the second conveying screw 2023 is pumped up to the surface of the developing sleeve 2026 by the magnetic force generated by the magnet. . Then, after the layer thickness is regulated by the doctor blade 2027 disposed so as to maintain a predetermined gap with the developing sleeve 2026, the developer is conveyed to the developing region facing the photosensitive drum 2011. Then, toner is attached to the electrostatic latent image formed on the photosensitive drum 2011 to form a toner image on the photosensitive drum 2011. The developer that has consumed toner by the development is returned to the second conveying screw 2023 as the developing sleeve 2026 rotates. The developer returned to the second conveying screw 2023 is returned to the first developer accommodating portion 2022.

  The detection result of the magnetic permeability of the developer by the toner concentration sensor 2025 is sent to a control unit (not shown) as a voltage signal. Since the magnetic permeability of the developer has a correlation with the toner concentration of the developer, the toner concentration sensor 2025 outputs a voltage having a value corresponding to the toner concentration. The control unit includes information storage means such as a RAM and stores Vref, which is a target value of the output voltage from the toner concentration sensor 2025, in the information storage means. The control unit compares the output voltage value from the toner density sensor 2025 with Vref. Then, a toner amount corresponding to the comparison result is supplied from the toner bottle 800 to the first developer accommodating portion 2022 of the developing unit 202 so that the toner concentration of the developer in the developing unit 202 is maintained at a desired value. . This toner supply control is performed for each color individually.

  An exposure unit 300 is disposed below the image forming process unit 200 shown in FIG. The exposure unit 300 serving as a latent image writing unit irradiates the surface of the photosensitive drum 2011 of each image forming process unit 200 with laser light L based on image information. Thereby, an electrostatic latent image is formed on the photosensitive drum 2011. Image information is information constituting image data to be printed on a recording sheet. The exposure unit 300 scans the laser light L emitted from the laser diode with a polygon mirror and irradiates the photosensitive drum 2011 via a plurality of optical lenses and mirrors. The exposure unit 300 can also be constituted by exposure means using an LED array.

  A paper feed tray 400 is disposed below the exposure unit 300. The paper feed tray 400 stores recording paper as a recording medium, and the paper feed roller 401 is in contact with the top recording paper. When the paper feed roller 401 is rotated counterclockwise at a predetermined timing by a driving means (not shown), the recording paper is discharged from the paper feed tray 400 and sent to the paper feed path. A plurality of transport rollers 402 are arranged in the paper feed path, and the recording paper sent to the paper feed path is transported upward by these transport rollers 402.

  A registration roller 403 is disposed in the paper feed path. When the recording paper is conveyed to just before the registration roller 403, the conveyance of the recording paper is temporarily stopped. The registration roller 403 is driven at a predetermined timing in accordance with the timing at which the toner image transferred onto the intermediate transfer belt 501 reaches the secondary transfer nip, and the recording paper is sent out toward the secondary transfer nip. The secondary transfer nip includes a belt driving roller 504 and a secondary transfer roller 506.

  Above each image forming process unit 200, an intermediate transfer unit 500 is provided that endlessly moves counterclockwise while stretching an intermediate transfer belt 501 that is a surface endless moving body.

  The intermediate transfer unit 500 serving as a transfer unit includes an intermediate transfer belt 501, a belt cleaning device 502, a primary transfer roller 503, a belt driving roller 504, a belt driven roller 505, a secondary transfer roller 506, and the like. The belt drive roller 504 also serves as a counter roller for the secondary transfer roller. The primary transfer roller 503 is disposed at a position where the photosensitive drums 2011 for each color face each other.

  The intermediate transfer belt 501 is endlessly moved counterclockwise by the rotational drive of the belt drive roller 504 while being stretched around the primary transfer roller 503, the belt drive roller 504, the belt driven roller 505, and the like.

  The primary transfer roller 503 is in contact with the photosensitive drum 2011 with the intermediate transfer belt 501 interposed therebetween to form a primary transfer nip. The primary transfer nip is constituted by the photosensitive drum 2011 and the primary transfer roller 503. The toner image on the photosensitive drum 2011 is transferred onto the intermediate transfer belt 501 by applying a transfer bias having a polarity opposite to that of the toner of the toner image formed on the photosensitive drum 2011 to the primary transfer roller 503. The toner images of the respective colors formed by the image forming process units 200 of the respective colors are sequentially primary transferred onto the intermediate transfer belt 501 so that a color image is formed on the intermediate transfer belt 501.

  A secondary transfer roller 506 is disposed at a position facing the belt drive roller 504, and the secondary transfer roller 506 is brought into contact with the belt drive roller 504 with a predetermined load by a spring load, thereby forming a secondary transfer nip. Is done. The secondary transfer nip includes a belt driving roller 504 and a secondary transfer roller 506.

  The color image formed on the intermediate transfer belt 501 is moved to the secondary transfer nip by the rotation of the intermediate transfer belt 501. In addition, the recording paper enters the secondary transfer nip from the registration roller 403 in synchronization with the entry of the color image into the secondary transfer nip.

  The color image formed on the intermediate transfer belt 501 is secondarily transferred to a recording sheet by a secondary transfer electric field and a nip pressure formed between the secondary transfer roller 506 and the belt driving roller 504. The electric field for secondary transfer is formed by applying a transfer bias having the same polarity as the toner image to the belt driving roller 504.

  On the intermediate transfer belt 501 after passing through the secondary transfer nip, a small amount of toner that has not been transferred to the recording paper remains and adheres. This is cleaned by the belt cleaning device 502. The belt cleaning device 502 scrapes and removes the transfer residual toner on the intermediate transfer belt 501 by bringing the cleaning blade into contact with the surface of the intermediate transfer belt 501. The transfer residual toner removed by the belt cleaning device 502 is accommodated in the waste toner bottle 600 and discarded.

  A fixing unit 700 is disposed above the secondary transfer nip. The fixing unit 700 includes a fixing roller 701 that includes an electromagnetic induction heat generating layer, a pressure roller 702 that contacts the fixing roller 701 with a predetermined pressure to form a predetermined nip width, a temperature sensor (not shown), and the like. ing. On the left side of the fixing roller 701, there is an IH coil 703 which is an electromagnetic induction means for generating heat in the electromagnetic induction heat generating layer in the fixing roller 701. The fixing roller 701 is heated by electromagnetic induction by the IH coil 703. The pressure roller 702 rotates in a clockwise direction by a drive source (not shown). Further, the fixing roller 701 rotates in the counterclockwise direction.

  The recording paper that has passed through the secondary transfer nip is separated from the intermediate transfer belt 501 and then sent to the fixing unit 700. Then, in the process of being conveyed from the lower side to the upper side while being sandwiched between the fixing nips of the fixing unit 700, it is heated by the fixing roller 701. At the same time, the toner image is fixed on the recording paper by being pressurized at the fixing nip. The recording paper subjected to the fixing process in this manner is stacked on the upper surface of the image forming apparatus 100 main body.

  Above the intermediate transfer unit 500, toner bottles 800 for each color that contain Y, M, C, and K toners are disposed. The toner of each color stored in the toner bottle 800 is appropriately supplied to the developing unit 202 of the image forming process unit 200 of each color. The toner bottle 800 can be detached from the main body of the image forming apparatus 100, and the toner bottle 800 can be replaced when the remaining amount of toner in the toner bottle 800 runs out.

  The intermediate transfer belt 501 of the present embodiment is configured by an elastic belt in which the entire belt layer or a part of the belt is an elastic member.

  The transfer of a color image using a resin belt has the following problems. A color image is usually formed with four color toners. In one color image, toner layers of 1 to 4 layers are formed. The toner layer passes through the primary transfer portion (the portion that performs transfer from the photosensitive drum 2011 to the intermediate transfer belt 501) and the secondary transfer portion (the portion that performs transfer from the intermediate transfer belt 501 to the recording paper). Under pressure, the cohesive force between the toners increases. When the cohesive force between the toners increases, the phenomenon of missing characters in the characters and missing edges in the solid portion image tends to occur. Since the resin belt has high hardness and does not deform in accordance with the toner layer, the toner layer is easily compressed, and a character dropout phenomenon is likely to occur. Recently, there is an increasing demand for forming full-color images on various papers, for example, Japanese paper or papers that are intentionally uneven.

  However, a paper with poor smoothness is liable to generate toner and voids at the time of transfer, and transfer loss is likely to occur. If the transfer pressure at the secondary transfer portion is increased to improve the adhesion, the condensing power of the toner layer is increased, and the above-described character void is generated.

  For this reason, the intermediate transfer belt 501 of this embodiment is formed of an elastic belt.

  The elastic belt is deformed corresponding to the toner layer and the paper having poor smoothness at the primary transfer portion and the secondary transfer portion. That is, since the elastic belt deforms following the local unevenness, good adhesion can be obtained without excessively increasing the transfer pressure with respect to the toner layer. In addition, a transfer image with excellent uniformity can be obtained even on paper with poor flatness.

<Example of rotational movement control of intermediate transfer belt 501>
Next, a control example for rotationally moving the intermediate transfer belt 501 of the present embodiment will be described with reference to FIGS. FIG. 3 is a diagram illustrating a configuration example of the intermediate transfer belt 501 of the present embodiment. FIG. 4 is a diagram illustrating a configuration example for reading the scale 900 provided on the intermediate transfer belt 501. FIG. 5 is a diagram illustrating a control configuration example for rotating the intermediate transfer belt 501. FIG. 6 is a diagram illustrating a processing operation example of the rotational movement control of the intermediate transfer belt 501 before the start of printing. FIG. 7 is a diagram illustrating a processing operation example of the rotational movement control of the intermediate transfer belt 501 during printing.

  The intermediate transfer belt 501 of this embodiment is provided with a scale 900 on the intermediate transfer belt 501 as shown in FIG. 3, and a scale slit of the scale 900 by a mark sensor 902 provided on the scale 900 as shown in FIG. Read 901. Based on the result read by the mark sensor 902, the control unit 903 shown in FIG. 5 controls the belt drive motor 904 to rotate and move the intermediate transfer belt 501. The belt drive motor 904 is a motor that drives the belt drive roller 504 shown in FIG.

  The mark sensor 902 is disposed at a position where the scale slit 901 of the scale 900 provided on the intermediate transfer belt 501 can be read. In the present embodiment, the mark sensor 902 is disposed above the transfer unit 500 as shown in FIG. However, this arrangement example is only an example, and any position where the scale slit 901 can be read may be used.

  For example, as shown in FIG. 4, the mark sensor 902 is configured using a reflective optical sensor having a pair of light emitting elements and light receiving elements. The scale 900 is configured such that the reflectance is different between the portion of the scale slit 901 and the other portion. As the output value of the mark sensor 902, a binary signal of High and Low is output depending on the difference in reflectance of the scale 900.

  For example, it is assumed that the mark sensor 902 is a type that outputs a high signal when light is received by a light receiving element. In this case, if the reflectance of the scale slit 901 part is higher than that of the other parts, the output signal from the mark sensor 902 is within the range of t shown in FIG. Output while passing through. As the intermediate transfer belt 501 rotates, the output of the mark sensor 902 repeats High and Low depending on the presence or absence of the portion of the scale slit 901 that passes through the detection range of the mark sensor 902. Accordingly, the surface speed of the intermediate transfer belt 501 can be detected by obtaining the time T from the time when the signal changes from Low to High until the next signal changes from Low to High. This is merely an example, and as long as the belt speed of the intermediate transfer belt 501 can be detected, the sensor type, scale type, belt speed detection method, and the like may be different. The belt speed of the intermediate transfer belt 501 may be detected.

  First, the control unit 903 controls the belt drive motor 904 to rotate at a basic speed. As the belt drive motor 904 rotates, the intermediate transfer belt 501 rotates, and the scale 900 on the surface of the intermediate transfer belt 501 also rotates. The mark sensor 902 reads the portion of the scale slit 901 of the scale 900 and feeds back the value to the control unit 903. The control unit 903 detects the belt speed of the intermediate transfer belt 501 from the output value of the mark sensor 902. If the belt speed is the same as the basic speed, the control unit 903 directly controls at the basic speed. If the belt speed is different from the basic speed, the difference is calculated, and the belt drive motor 904 is controlled with a value obtained by adding the difference to the basic speed.

  In the image forming apparatus 100 of the present embodiment, before starting printing, the control unit 903 turns on the belt drive motor 904 so as to rotate the intermediate transfer belt 501 at the basic speed V as shown in FIG. Step S1). At that time, the control unit 903 outputs the basic speed V to the belt drive motor 904 (step S2). As a result, the intermediate transfer belt 501 rotates at the basic speed V.

  In addition, the control unit 903 turns on the heater 905 that is a heating unit provided above the intermediate transfer belt 501 at the target temperature T (step S3). In the present embodiment, a heater 905 is provided above the intermediate transfer unit 500 to heat the transfer belt 501. The position where the heater 905 is provided is not particularly limited, and can be provided at any position as long as the intermediate transfer belt 501 can be heated.

  However, it is preferable to arrange the heater 905 immediately after the secondary transfer and before the primary transfer as shown in FIG. Thereby, the belt speed fluctuation of the intermediate transfer belt 501 can be reduced. This is because the temperature sensor 906 detects the temperature change that occurs when the toner image on the intermediate transfer belt 501 is transferred to the recording paper in the secondary transfer, and the heater is based on the detection result. This is because the intermediate transfer belt 501 can be heated at 905. Thereby, the temperature fluctuation of the intermediate transfer belt 501 can be efficiently reduced.

  It is also possible to install the heater 905 inside the belt driving roller 504. By heating the temperature change generated by the recording paper in the secondary transfer unit by the heater 905 installed inside the belt driving roller 504, the temperature fluctuation of the intermediate transfer belt 501 can be reduced uniformly and efficiently.

  The heater 905 is preferably an IH heater. Thereby, the responsiveness of temperature control can be improved. As a result, even when the linear velocity of the image forming apparatus 100 is fast, the uniformity of the temperature in the belt circumferential direction of the intermediate transfer belt 501 can be improved. In addition, the adjustment time for determining the target temperature T can be reduced, and the time that the user waits (downtime before starting printing) can be reduced. Furthermore, power consumption can be reduced.

Next, the control unit 903 detects the output of the mark sensor 902 (step S4), and grasps the actual speed (belt surface speed V1) of the belt surface of the intermediate transfer belt 501 (step S5). Next, the intermediate transfer belt 501 is rotated for a predetermined time to grasp the belt surface speed deviation Vσ (step S6). The belt surface speed deviation Vσ is a square root of a total value of t = 1 to T of a value obtained by squaring the difference between the basic speed V and the belt surface speed V1 _t at a certain time t (t = 1 to T). It is the value obtained by the following formula.

  The control unit 903 compares the value of the belt surface speed deviation Vσ with the value of the reference speed deviation Σ (step S7). The reference value of the speed deviation Σ is set in advance. When the value of the belt surface speed deviation Vσ is equal to or less than the reference speed deviation Σ (Vσ ≦ Σ) (step S8 / No), the control unit 903 starts printing (step S9).

  When the belt surface speed deviation Vσ is larger than the reference speed deviation Σ (Vσ> Σ) (step S8 / Yes), the belt target temperature T of the intermediate transfer belt 501 is set to T ′ = T + ΔT. (Step S10). The value of ΔT can be arbitrarily changed. Then, it is determined whether or not the changed target temperature T ′ is lower than T max (step S11). T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. If the temperature is further increased, it is a limit temperature at which cleaning failure occurs. When the changed target temperature T ′ is lower than T max (step S11 / YES), the heater 905 is turned on at the changed target temperature T ′ (step S12). Then, the process returns to step S4, and the output of the mark sensor 902 is detected (step S4).

  When the target temperature T ′ after the change is equal to or higher than T max (step S11 / No), the target temperature T ′ after the change is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step S13). Then, printing is started (step S9).

  Before starting printing, the image forming apparatus 100 of the present embodiment performs the control operation shown in FIG. 6 so that the belt surface speed deviation Vσ of the intermediate transfer belt 501 is smaller than the reference speed deviation Σ. Can be started. However, T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt, and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. is there. Therefore, even when T ′> T max and the belt surface speed deviation Vσ is smaller than the reference speed deviation Σ, the heater 905 of the intermediate transfer belt 501 is lit at T max and printing is started. Will be.

  In FIG. 6, when the changed target temperature T ′ is equal to or higher than T max (step S11 / No), the changed target temperature T ′ is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step S13), and printing is started (step S9). However, after the heater 905 of the intermediate transfer belt 501 is turned on at Tmax, the processing in steps S4 to S7 is performed, and the value of the belt surface speed deviation Vσ is compared with the reference speed deviation Σ (step S7). ). If the value of the belt surface speed deviation Vσ is larger than the reference speed deviation Σ (Vσ> Σ), an error notification is given to the user operating the image forming apparatus 100 or the system administrator, or printing is performed. It is also possible not to perform. Even if the heater 905 of the intermediate transfer belt 501 is lit at T max, if the belt surface speed deviation Vσ does not fall below the standard speed deviation Σ (Vσ ≦ Σ), paper feed such as banding and shock jitter The density unevenness in the direction perpendicular to the direction may occur. For this reason, it is preferable to notify the user or system administrator operating the image forming apparatus 100 of an error or not to perform printing. An error notification method is not particularly limited, and an arbitrary method is possible. In the case of notifying the system administrator of an error, information (for example, an e-mail address) of the system administrator who performs the error notification is set in the image forming apparatus 100 in advance, and the error notification is performed based on the information. Will do.

  After starting printing, the image forming apparatus 100 according to the present embodiment, as shown in FIG. 7, checks whether the belt drive motor 904 is OFF (step A1). If the belt drive motor 904 is OFF (step A1 / Yes), printing is terminated (step A2). If the belt drive motor 904 is ON (step A1 / No), the output of the temperature sensor 906 provided above the intermediate transfer belt 501 is detected (step A3), and the temperature of the belt surface of the intermediate transfer belt 501 is detected. Know T1 (step A4). In this embodiment, a temperature sensor 906 is provided above the intermediate transfer unit 500, and the temperature of the belt surface of the transfer belt 501 is measured. The position where the temperature sensor 906 is provided is not particularly limited, and can be provided at any position as long as the temperature of the intermediate transfer belt 501 can be measured. However, the temperature sensor 906 is preferably provided immediately after the secondary transfer. As a result, the temperature sensor 906 can detect a temperature change caused by transferring the toner image on the intermediate transfer belt 501 to the recording paper in the secondary transfer at a position immediately after the secondary transfer.

  Next, the control unit 903 compares the belt surface temperature T1 with the reference target temperature value T (step A5). When the belt surface temperature T1 is equal to the target temperature value T (T1 = T) (step A6 / Yes), the control unit 903 turns on the heater 905 with the target temperature value T (step A11). Then, the process returns to step A1 to check whether or not the belt drive motor 904 is OFF (step A1).

  If the belt surface temperature T1 and the target temperature value T are not the same (T1 ≠ T) (step A6 / No), the difference T2 between the belt surface temperature T1 and the target temperature value T (T2 = T−T1) ) (Step A7). If the obtained difference T2 is T2> 0 (step A8 / YES), T = T1 + T2 is set (step A9), and the heater 905 is turned on with the value of T (step A11). Accordingly, the heater 905 can be turned on at the target temperature value T. If the obtained difference T2 is T2 <0 (step A8 / No), T = T1-T2 (step A10), and the heater 905 is turned on with the value of T (step A11). Accordingly, the heater 905 can be turned on at the target temperature value T.

  After starting printing, the image forming apparatus 100 according to the present embodiment performs the control operation shown in FIG. 7 to set the belt surface temperature of the intermediate transfer belt 501 to the target temperature T (the value set in step S3 in FIG. 6). ) Can be operated constantly.

  The belt surface speed deviation Vσ (difference between the basic speed V and the belt surface speed V1) of the intermediate transfer belt 501 described above is caused by several factors. The fluctuation frequency of the speed fluctuation includes a low frequency component and a high frequency component. And exist. In order to correct both the low frequency component and the high frequency component, it is necessary to adjust the correction frequency range to the high frequency side, and a highly accurate and complicated control circuit is required. This is because the correction accuracy has a problem with the control loop period and the detection accuracy of the sensor. Specifically, in order to correct the high frequency period, it is necessary to configure the control loop period with a period earlier than that. In general, in order to be within the control range, it is necessary to perform correction with a period of several tens of times the target correction frequency. Therefore, in order to correct the high frequency period, the control loop period must be considerably shortened, and as a result, it is necessary to suppress the accuracy and variation of the constituent parts. Along with this, it is necessary to improve the accuracy of the sensor to be detected, and the scale 900 provided on the intermediate transfer belt 501 also requires high resolution, high accuracy, and processing becomes difficult. End up. As a result, in order to achieve these, it becomes necessary to construct a high-cost system.

  In this embodiment, attention is paid to the temperature change of the intermediate transfer belt 501 as a factor causing the speed change of the intermediate transfer belt 501, and the speed change of the intermediate transfer belt 501 accompanying the temperature change of the intermediate transfer belt 501 is corrected. ing. In particular, when an elastic belt is used as the intermediate transfer belt 501, the elastic modulus changes greatly depending on the temperature. For this reason, the nip pressure changes in the primary transfer portion and the secondary transfer portion, and the speed fluctuation occurs in the intermediate transfer belt 501. FIG. 8 shows the belt temperature t of the intermediate transfer belt 501 on the horizontal axis and the belt speed deviation σ of the intermediate transfer belt 501 during the pre-printing adjustment operation on the vertical axis. As the belt temperature t increases, the belt speed deviation σ of the intermediate transfer belt 501 decreases. At the belt temperature T, the belt speed deviation σ takes the minimum value Σ, and when the belt temperature t is increased further, the belt speed deviation σ again It can be seen that the belt speed deviation σ increases. Note that T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. If the temperature is further increased, cleaning failure occurs. .

  FIG. 9 shows the belt temperature t on the horizontal axis and the banding evaluation value on the vertical axis. The banding evaluation value is worse as the number is larger. When the image was actually output at the target temperature t during paper feeding and the density unevenness was evaluated, it was confirmed that the density unevenness was indeed the best at the temperature T. Further, it has been confirmed that the horizontal band-shaped density unevenness (shock jitter) generated when the recording paper enters the secondary transfer portion is also improved.

  The image forming apparatus 100 of the present embodiment can correct both the low frequency component and the high frequency component by combining the belt temperature control described above and the speed control of the intermediate transfer belt 501 by the mark sensor 902. It becomes. Further, by controlling the speed of the intermediate transfer belt 501 by the mark sensor 902 only to the low frequency component, the shift amount of the moving speed of the intermediate transfer belt 501 can be detected with higher accuracy and more stable. Speed control can be performed.

<Operation / Effect of Image Forming Apparatus 100 of Present Embodiment>
As described above, the image forming apparatus 100 according to the present embodiment detects the belt surface speed deviation Vσ of the intermediate transfer belt 501, and adjusts the temperature of the heater 905 so that the belt surface speed deviation Vσ becomes constant. The temperature of the belt 501 is adjusted. Thereby, the belt surface speed deviation Vσ of the intermediate transfer belt 501 due to the temperature change of the intermediate transfer belt 501 can be reduced. As a result, an image having good in-plane uniformity without banding or shock jitter can be stably formed.

  In the above-described processing operation example, even if the belt surface temperature of the intermediate transfer belt 501 is operated at the target temperature T, if the paper type or paper thickness of the recording paper to be printed is different, banding or shock jitter The degree of occurrence may not improve. This is because even if the behavior of the intermediate transfer belt 501 during the adjustment operation before printing is stable, the behavior of the intermediate transfer belt 501 during printing is not stable. This is because the optimum temperature changes because the heat capacity and the thermal conductivity between the recording paper and the intermediate transfer belt 501 change due to the difference in thickness and surface property of the recording paper to be printed.

  For this reason, the image forming apparatus 100 of the present embodiment stores the correction values shown in FIG. 10 in the information storage unit. The correction values shown in FIG. 10 indicate a plurality of correction values corresponding to the paper type and paper thickness. The control unit 903 refers to the correction value shown in FIG. 10 and uses the correction value according to the paper type and paper thickness used for printing, and the target of the intermediate transfer belt 501 determined in the processing operation example shown in FIG. Correct the temperature T. As a result, it is possible to improve the degree of occurrence of banding and shock jitter regardless of the paper type and paper thickness used for printing.

For example, when the target temperature T of the intermediate transfer belt 501 determined in the processing operation example shown in FIG. 6 is 30 ° C., the recording paper used for printing is coated paper, and the paper thickness is 250 g / m ² , the correction amount is + 20%, and the corrected temperature is 30 ° C. × 1.2 = 36 ° C. The correction amount is an example, and may be set for each type of individual recording paper. Although FIG. 10 shows the correction value corresponding to the type of recording paper, the target temperature T corresponding to the type of recording paper can be stored in advance in the information storage means. In this case, the control unit 903 refers to the information storage unit, identifies the target temperature T corresponding to the type of recording paper used for printing, and sets the identified target temperature in step S3 in FIG. .

  Further, depending on the installation environment of the image forming apparatus 100, even if the belt temperature of the intermediate transfer belt 501 is equal to or lower than T max before starting printing, T max may be exceeded during continuous printing. T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt, and the cleaning property of the intermediate transfer belt 501 starts to decrease. It is defined in advance. In this case, the toner image transferred to the intermediate transfer belt 501 starts to melt, and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. Therefore, if the belt temperature of the intermediate transfer belt 501 exceeds T max, image formation is performed. Stop operation. Then, it is preferable that the rotation operation of the intermediate transfer belt 501 is performed so that the image forming operation is resumed after the belt temperature of the intermediate transfer belt 501 is lowered to the target temperature T. Thereby, it is possible to form a stable image without abnormal images such as defective cleaning due to excessive heating.

  When the intermediate transfer belt 501 is heated by the heater 905, the temperature of the photosensitive drum 2011 rises through the primary transfer nip, the surface potential of the photosensitive drum 2011 changes, the development potential changes, and the image density varies. May end up. In particular, when the image forming apparatus 100 is installed in a low-temperature and low-humidity environment, the above phenomenon occurs remarkably immediately after the power is turned on. In order to prevent this, a temperature sensor 203 for detecting the surface temperature of the photosensitive drum 2011 is installed, and the surface temperature of the photosensitive drum 2011 becomes equal to the belt temperature of the intermediate transfer belt 501 during the pre-printing operation. It is preferable to perform control so that the image forming operation is started from the beginning. Thereby, the temperature fluctuation of the photosensitive drum 2011 during printing can be suppressed, and the image density stability can be improved. Note that the installation position of the temperature sensor 203 for detecting the surface temperature of the photosensitive drum 2011 can be installed at any position as long as the surface temperature of the photosensitive drum 2011 can be detected.

(Second Embodiment)
Next, a second embodiment will be described.

  In the first embodiment, the belt surface speed deviation Vσ of the intermediate transfer belt 501 is detected, and the temperature of the heater 905 is adjusted so that the belt surface speed deviation Vσ becomes constant, thereby adjusting the temperature of the intermediate transfer belt 501. I have decided.

  However, when the elastic layer of the intermediate transfer belt 501 is thick, even if the belt surface speed deviation Vσ of the intermediate transfer belt 501 becomes constant, the state of the belt surface is non-uniform, so the belt is formed by the image forming apparatus 100. The image may not be an image with good in-plane uniformity.

  In the second embodiment, as shown in FIG. 11, a torque sensor 907 that detects the torque fluctuation of the belt drive motor 904 is provided, and the torque fluctuation of the belt drive motor 904 that drives the intermediate transfer belt 501 is detected. The torque sensor 907 is attached to the belt drive motor 904. Then, the control unit 903 adjusts the temperature of the intermediate transfer belt 501 by adjusting the temperature of the heater 905 so that the torque fluctuation detected by the torque sensor 907 is constant. Thereby, the speed fluctuation of the intermediate transfer belt 501 due to the temperature change of the intermediate transfer belt 501 can be reduced. As a result, an image having good in-plane uniformity without banding or shock jitter can be stably formed.

  FIG. 11 is a diagram illustrating an example of a control configuration for rotating the intermediate transfer belt 501. First, the control unit 903 controls the belt drive motor 904 to rotate at the basic speed V. As the belt drive motor 904 rotates, the intermediate transfer belt 501 rotates. The torque sensor 907 detects the torque fluctuation of the belt drive motor 904 and notifies the control unit 903 of the detection result. The control unit 903 adjusts the temperature of the intermediate transfer belt 501 by adjusting the temperature of the heater 905 so that the torque fluctuation detected by the torque sensor 907 is constant. Thereby, the speed fluctuation of the intermediate transfer belt 501 due to the temperature change of the intermediate transfer belt 501 can be reduced. As the torque sensor 907, any type of torque sensor such as a non-contact type or a contact type can be used as long as the torque fluctuation of the belt drive motor 904 can be detected.

  Next, a processing operation example of the rotational movement control of the intermediate transfer belt 501 before starting printing will be described with reference to FIG. FIG. 12 is a diagram illustrating a processing operation example of the rotational movement control of the intermediate transfer belt 501 before the start of printing.

  In the image forming apparatus 100 of the present embodiment, before starting printing, the control unit 903 turns on the belt drive motor 904 to rotate the intermediate transfer belt 501 at the basic speed V as shown in FIG. Step B1). At that time, the control unit 903 outputs the basic speed V to the belt drive motor 904 (step B2). As a result, the intermediate transfer belt 501 rotates at the basic speed V.

  Further, the control unit 903 turns on the heater 905, which is a heating unit provided above the intermediate transfer belt 501, at the target temperature T (step B3).

Next, the control unit 903 detects the output of the drive motor torque sensor 907 (step B4), and grasps the actual torque F0 of the belt drive motor 904 (step B5). Next, the intermediate transfer belt 501 is rotated for a predetermined time, and the drive motor torque deviation Fσ is grasped (step B6). The drive motor torque deviation Fσ is a value t obtained by squaring the difference between the reference torque F when the intermediate transfer belt 501 is rotated at the basic speed V and the actual torque F0 _t at a certain time t (t = 1 to T). = 1 to T is the square root of the total value, and is a value obtained by the following equation.

  The control unit 903 compares the value of the drive motor torque deviation Fσ with the value of the reference torque deviation Σ (step B7). The reference value of torque deviation Σ is set in advance. When the value of the drive motor torque deviation Fσ is equal to or less than the reference torque deviation Σ (Fσ ≦ Σ) (step B8 / No), the control unit 903 starts printing (step B9).

  When the value of the drive motor torque deviation Fσ is larger than the reference torque deviation Σ (Fσ> Σ) (Step B8 / Yes), the belt target temperature T of the intermediate transfer belt 501 is set to T ′ = T + ΔT. (Step B10). The value of ΔT can be arbitrarily changed. Then, it is determined whether or not the changed target temperature T ′ is less than T max (step B11). T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. If the temperature is further increased, it is a limit temperature at which cleaning failure occurs. When the changed target temperature T ′ is less than T max (step B11 / Yes), the heater 905 is turned on at the changed target temperature T ′ (step B12). Then, returning to step B4, the output of the drive motor torque sensor 907 is detected (step B4).

  When the changed target temperature T ′ is equal to or higher than T max (step B11 / No), the changed target temperature T ′ is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step B13). Then, printing is started (step B9).

  Before starting printing, the image forming apparatus 100 according to the present embodiment performs the control operation shown in FIG. 12 so that the drive motor torque deviation Fσ of the belt drive motor 904 is smaller than the reference torque deviation Σ. Can be started. However, T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt, and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. is there. Therefore, even when T ′> T max and the drive motor torque deviation Fσ is smaller than the reference torque deviation Σ, the heater 905 of the intermediate transfer belt 501 is lit at T max and printing is started. Will do.

  In FIG. 12, when the changed target temperature T ′ is equal to or higher than T max (step B11 / No), the changed target temperature T ′ is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step B13), and printing is started (step B9). However, after the heater 905 of the intermediate transfer belt 501 is turned on at Tmax, the processing of step B4 to step B7 is performed, and the value of the drive motor torque deviation Fσ is compared with the value of the reference torque deviation Σ (step B7 ). If the value of the drive motor torque deviation Fσ is larger than the reference torque deviation Σ (Fσ> Σ), an error notification is given to the user or system administrator who operates the image forming apparatus 100, or printing is performed. It is also possible not to perform. If the heater 905 of the intermediate transfer belt 501 is lit at T max and the drive motor torque deviation Fσ does not fall below the reference torque deviation Σ (Fσ ≤ Σ), paper feed such as banding and shock jitter The density unevenness in the direction perpendicular to the direction may occur. For this reason, it is preferable to notify the user or system administrator operating the image forming apparatus 100 of an error or not to perform printing. An error notification method is not particularly limited, and an arbitrary method is possible. In the case of notifying the system administrator of an error, information (for example, an e-mail address) of the system administrator who performs the error notification is set in the image forming apparatus 100 in advance, and the error notification is performed based on the information. Will do.

  Note that the image forming apparatus 100 according to the present embodiment performs the control operation illustrated in FIG. 7 described in the first embodiment after starting printing, so that the belt surface temperature of the intermediate transfer belt 501 is set to the target temperature T. It is possible to operate at a constant value (the value set in step B3 in FIG. 11).

  In this embodiment, attention is paid to the temperature change of the intermediate transfer belt 501 as a factor causing the speed change of the intermediate transfer belt 501, and the speed change of the intermediate transfer belt 501 accompanying the temperature change of the intermediate transfer belt 501 is corrected. ing. In particular, when an elastic belt is used as the intermediate transfer belt 501, the elastic modulus changes greatly depending on the temperature. For this reason, the nip pressure changes in the primary transfer portion and the secondary transfer portion, and the speed fluctuation occurs in the intermediate transfer belt 501. FIG. 13 shows the belt temperature t of the intermediate transfer belt 501 on the horizontal axis and the drive motor torque deviation σ of the belt drive motor 904 during the pre-printing adjustment operation on the vertical axis. As the belt temperature t rises, the drive motor torque deviation σ of the belt drive motor 904 decreases, and at the belt temperature T, the drive motor torque deviation σ takes the minimum value Σ and further increases the belt temperature t. It can be seen again that the drive motor torque deviation σ increases. Note that T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. If the temperature is further increased, cleaning failure occurs. .

  FIG. 9 shows the belt temperature t on the horizontal axis and the banding evaluation value on the vertical axis. The banding evaluation value is worse as the number is larger. When the image was actually output at the target temperature t during paper feeding and the density unevenness was evaluated, it was confirmed that the density unevenness was indeed the best at the temperature T. Further, it has been confirmed that the horizontal band-shaped density unevenness (shock jitter) generated when the recording paper enters the secondary transfer portion is also improved.

<Operation / Effect of Image Forming Apparatus 100 of Present Embodiment>
As described above, the image forming apparatus 100 according to the present embodiment detects the drive motor torque deviation σ of the belt drive motor 904 that drives the intermediate transfer belt 501. Then, the temperature of the intermediate transfer belt 501 is adjusted by adjusting the temperature of the heater 905 so that the drive motor torque deviation σ becomes constant. Thereby, the belt surface speed deviation Vσ of the intermediate transfer belt 501 due to the temperature change of the intermediate transfer belt 501 can be reduced. As a result, an image having good in-plane uniformity without banding or shock jitter can be stably formed.

  In the above-described embodiment, the drive motor torque deviation σ of the belt drive motor 904 that drives the intermediate transfer belt 501 is detected. However, the intermediate transfer belt 501 may be supported by a plurality of belt driven rollers 505 in addition to the belt driving roller 504 connected to the belt driving motor 904. In this case, the drive motor torque deviation of the belt drive motor 904 and the driven roller torque deviation of each belt driven roller 505 are detected. It is also possible to adjust the temperature of the intermediate transfer belt 501 by adjusting the temperature of the heater 905 so that the sum (torque total deviation) Fσ ′ of the drive motor torque deviation and each driven roller torque deviation is constant. is there. In this case, a torque sensor for detecting the driven roller torque deviation of each belt driven roller 505 is attached to each belt driven roller 505. An example of the processing operation in this case is shown in FIG. FIG. 14 is a diagram illustrating a processing operation example of the rotational movement control of the intermediate transfer belt 501 before the start of printing.

  Before starting printing, as shown in FIG. 14, the control unit 903 turns on the belt drive motor 904 so as to rotate the intermediate transfer belt 501 at the basic speed V (step C1). At that time, the control unit 903 outputs the basic speed V to the belt drive motor 904 (step C2). As a result, the intermediate transfer belt 501 rotates at the basic speed V.

  In addition, the control unit 903 turns on the heater 905, which is a heating unit provided above the intermediate transfer belt 501, at the target temperature T (step C3).

Next, the control unit 903 detects the output of the torque sensor 907 attached to the belt drive motor 904 and the torque sensor attached to each belt driven roller 505 (step C4). Then, the actual torque F0 of the belt drive motor 904 is grasped (step C5), or the actual torques F1 to Fn (n is an arbitrary integer) of each belt driven roller 505 are grasped (step C'5). Next, the intermediate transfer belt 501 is rotated for a predetermined time, and a total torque deviation Fσ ′, which is the sum of the driving motor torque and each driven roller torque deviation, is grasped (step C6). The drive motor torque deviation Fσ is a value t obtained by squaring the difference between the reference torque F when the intermediate transfer belt 501 is rotated at the basic speed V and the actual torque F0 _t at a certain time t (t = 1 to T). = 1 to T is the square root of the total value, and is a value obtained by the following equation.

  Further, the driven roller torque deviation Fσ ′ is equal to the reference torque Fn ′ of each driving roller when the intermediate transfer belt 501 is rotated at the basic speed V and the actual torques F1 to Fn at a certain time t (t = 1 to T). Is the square root of the total value of t = 1 to T of the value obtained by squaring the difference between the two, and is a value obtained by the following equation.

  The control unit 903 compares the value of the torque total deviation Fσ ′ with the reference value of the torque total deviation Σ ′ (step C7). The reference torque total deviation Σ 'is set in advance. When the value of the torque total deviation Fσ ′ is equal to or less than the value of the reference torque total deviation Σ ′ (Fσ ′ ≦ Σ ′) (step C8 / No), the control unit 903 starts printing (step C9).

  If the total torque deviation Fσ ′ is larger than the reference total torque deviation Σ ′ (Fσ ′> Σ ′) (step C8 / Yes), the target belt temperature T of the intermediate transfer belt 501 is set to T ′. = T + ΔT (Step C10). The value of ΔT can be arbitrarily changed. Then, it is determined whether or not the changed target temperature T ′ is less than T max (step C11). T max is a temperature at which the toner image transferred to the intermediate transfer belt 501 starts to melt and the cleaning property of the intermediate transfer belt 501 starts to deteriorate. If the temperature is further increased, it is a limit temperature at which cleaning failure occurs. When the changed target temperature T ′ is lower than T max (step C11 / YES), the heater 905 is turned on at the changed target temperature T ′ (step C12). Then, returning to Step C4, the output of the torque sensor 907 attached to the belt drive motor 904 and the torque sensor attached to each belt driven roller 505 is detected (Step C4).

  When the changed target temperature T ′ is equal to or higher than T max (step C11 / No), the changed target temperature T ′ is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step C13). Then, printing is started (step C9).

  Before starting printing, the control operation shown in FIG. 14 is performed, so that printing can be started in a state where the total torque deviation Fσ ′ is smaller than the reference total torque deviation Σ ′.

  In FIG. 14, when the changed target temperature T ′ is equal to or higher than T max (step C11 / No), the changed target temperature T ′ is changed to T max. Then, the heater 905 of the intermediate transfer belt 501 is turned on at T max (step C13), and printing is started (step C9). However, after the heater 905 of the intermediate transfer belt 501 is turned on at Tmax, the processing of Step C4 to Step C7 is performed, and the value of the torque total deviation Fσ ′ is compared with the value of the reference torque total deviation Σ ′ ( Step C7). If the torque total deviation Fσ ′ is larger than the reference torque total deviation Σ ′ (Fσ ′> Σ ′), an error notification is sent to the user or system administrator who operates the image forming apparatus 100. It is also possible to perform or not perform printing. Even if the heater 905 of the intermediate transfer belt 501 is lit at T max, if the torque total deviation Fσ 'does not fall below the reference torque total deviation Σ' (Fσ '≤ Σ'), banding or shock Density unevenness in the direction perpendicular to the paper feed direction such as jitter may occur. For this reason, it is preferable to notify the user or system administrator operating the image forming apparatus 100 of an error or not to perform printing. An error notification method is not particularly limited, and an arbitrary method is possible. In the case of notifying the system administrator of an error, information (for example, an e-mail address) of the system administrator who performs the error notification is set in the image forming apparatus 100 in advance, and the error notification is performed based on the information. Will do.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

  For example, the control operation in each apparatus constituting the image forming apparatus of the above-described embodiment can be executed using hardware, software, or a combination of both.

  In the case of executing processing using software, it is possible to install and execute a program in which a processing sequence is recorded in a memory in a computer incorporated in dedicated hardware. Alternatively, it can be installed in a memory in a general-purpose computer capable of executing various processes and executed.

  For example, the program can be recorded in advance on a hard disk or ROM (Read Only Memory) as a recording medium. Alternatively, the program can be stored (recorded) temporarily or permanently in a removable recording medium. Such a removable recording medium can be provided as so-called package software. Examples of the removable recording medium include various recording media such as a magnetic disk and a semiconductor memory.

  The program is installed in the computer from the removable recording medium as described above. In addition, it is wirelessly transferred from the download site to the computer. In addition, it is transferred to a computer via a network by wire.

  In addition, each apparatus constituting the image forming apparatus of the above-described embodiment is not limited to performing processing in time series according to the processing operation described in the above-described embodiment. For example, it is possible to construct the processing capability of a device that executes processing, or to execute processing in parallel or individually as necessary.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 200 Image forming process unit 501 Intermediate transfer belt 503 Primary transfer roller 504 Belt drive roller 505 Belt driven roller 506 Secondary transfer roller 902 Mark sensor 903 Control unit 904 Belt drive motor 905 Heater 906 Temperature sensor 907 Torque sensor

JP 2001-154504 A Japanese Laid-Open Patent Publication No. 2005-250331 JP 2010-210656 A JP 2006-10985 A

Claims (6)

A primary transfer means for transferring a toner image formed on the image carrier to an intermediate transfer member;
Secondary transfer means for transferring the toner image transferred to the intermediate transfer member to a transfer material;
Detecting means for detecting a speed fluctuation of the intermediate transfer member;
Temperature adjusting means for adjusting the temperature of the intermediate transfer member so that the speed fluctuation is constant;
An image forming apparatus comprising: A heating means for heating the intermediate transfer member;
The temperature adjusting means is
The image forming apparatus according to claim 1, wherein a temperature at which the intermediate transfer member is heated by the heating unit is adjusted. The temperature adjusting means is
The image forming apparatus according to claim 2, wherein a temperature at which the intermediate transfer member is heated by the heating unit is changed according to a type of the transfer material.   When the temperature of the intermediate transfer member exceeds a predetermined limit temperature, the image forming operation is stopped, and the image forming operation is restarted after the temperature of the intermediate transfer member is lowered to a predetermined temperature. The image forming apparatus according to any one of claims 1 to 3. Having detection means for detecting the temperature of the image carrier,
5. The image formation according to claim 1, wherein an image forming operation is started when a temperature of the image carrier and a temperature of the intermediate transfer body become equal. apparatus. The detection means includes
The torque fluctuation of at least one of a torque fluctuation of a motor driving the intermediate transfer member and a torque fluctuation of a driven roller driven by the driving of the motor is detected. The image forming apparatus according to claim 1.

Images