JP2013064865A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device in which a deviation of a transfer roller in a transfer pressure axis direction caused by installation error of a belt surface speed detection sensor is suppressed in a prescribed allowable value.SOLUTION: A sensor holding member 130 for supporting a surface speed detection device 110 having scale sensors 6A and 6B, or a sensor substrate 127 which is integrally formed with the scale sensors 6A and 6B, is brought into contact with an intermediate transfer belt 10. An adjustment mechanism 160 for adjusting a pressing force of a pressing mechanism 140, the pressing force being generated by a resilience of a spring 143, is provided to the pressing mechanism 140 of a primary transfer roller 62K and a primary transfer roller 62C at one of or both of a belt moving direction upstream side of the surface speed detection device 110 and downstream side thereof.

Description

  The present invention relates to an electrophotographic image forming apparatus including a belt surface speed detection sensor for detecting a belt surface speed of an endless belt stretched through a transfer nip portion.

  Conventionally, in an electrophotographic image forming apparatus such as a printer, a fax machine, and a copying machine, a deviation (hereinafter, referred to as a transfer pressure) in a transfer nip portion in a direction parallel to an axial direction of a transfer roller (hereinafter referred to as an axial direction). It is known that there is a deviation in image density if there is a transfer pressure axis direction deviation). In the configuration using an endless belt such as an intermediate transfer belt or a transfer conveyance belt stretched through a transfer nip portion, the following has been conventionally known.

  Deviations at both ends of the axial center positions of other transfer rollers and belt stretching members arranged in the immediate vicinity of the upstream or downstream side in the belt movement direction of a certain transfer roller with respect to a predetermined axial position If this occurs, the transfer pressure axial deviation may be affected. This is due to the following reason. For example, the transfer roller is in contact with the photosensitive member via an endless belt from below, and the belt stretching member disposed immediately upstream of the transfer roller in the belt moving direction is also in contact with the endless belt from below. To do. Only one end side of the axial center of the upstream belt stretching member in contact with the above is attached in a state where it moves upward from the predetermined axial position due to low processing accuracy of each member. As a result, an axial position deviation occurs between the other end side attached at a predetermined position. In addition, one end side of the contact position with the endless belt moves upward. The trajectory of the endless belt on one end side moves in a direction closer to the photoconductor than the predetermined trajectory. When moving in such a direction, the force in the direction in which the endless belt presses the photosensitive member or the like increases due to the tension of the endless belt, and the transfer pressure on the one end side increases. Further, when only one end side of the shaft center of the belt stretching member is attached while being moved downward from the predetermined shaft center position, the one end side of the contact position with the endless belt also moves downward. When the endless belt trajectory on one end side moves away from the photoconductor etc. than the predetermined trajectory, the force in the direction in which the endless belt presses the photoconductor etc. decreases due to the tension of the endless belt. The transfer pressure decreases.

  Further, a deviation in the axial direction of the belt tension (hereinafter referred to as an axial belt tension deviation) may occur, which may affect the transfer pressure axial deviation. This is due to the following reason. For example, when applying the transfer pressure by abutting the transfer roller against the photoconductor, the transfer roller may be offset and wound around the photoconductor for the purpose of preventing abnormalities such as discharge. With such a configuration, if there is an axial belt tension deviation, a deviation occurs in the axial direction of the belt tension in the direction connecting the center line of the photoreceptor and the transfer roller. It will have an effect. In such a case as well, the axial position deviation of the transfer roller and the belt stretching member arranged immediately upstream or downstream of the transfer roller overlaps, so that the influence on the transfer pressure axial deviation becomes large. There is a case. Therefore, conventionally, the processing accuracy of each member has been increased so that the deviation in the axial direction of the transfer pressure generated in this way falls within a predetermined allowable range in which no deviation occurs in the image density.

  Further, in the configuration using the endless belt in this way, in order to suppress the fluctuation in the moving direction speed of the endless belt, the belt moving direction speed of the endless belt is detected, and feedback control is performed based on the detected belt moving direction speed. Image forming apparatuses are widely used. There are two types of belt movement direction speed detection sensors. One is to detect the number of rotations by attaching an encoder to the shaft of the driven roller, and the other is to process the belt surface by processing a scale etc. This is a method using a belt surface speed detection sensor for detecting the speed. When the encoder is attached to the shaft of the driven roller, the flare component of the driven roller cannot be detected, and the accuracy is often lower than the method using the belt surface speed detection sensor. A method using a detection sensor is widely used. Here, when the belt surface speed detection sensor is used, the sensor holding member is brought into contact with the belt surface, and an elastic member is provided on the opposite side of the belt so as to sandwich the belt. Often the detection is not affected. Conventionally, it is desirable to place the belt surface speed measurement location near the transfer roller from the viewpoint of preventing color misregistration, etc., and if there are multiple transfer rollers in a color compatible machine, install between the transfer rollers. It is known that it is more preferable.

  However, when the conventional belt surface speed detection sensor is used, there are the following problems. When the belt surface speed detection sensor is installed in a state where it is deviated in a direction perpendicular to the endless belt, the endless belt trajectory deviates from the predetermined trajectory because the endless belt is sandwiched between sensor holding members and the like. Become. That is, the endless belt trajectory may deviate from the predetermined trajectory due to the installation error of the belt surface speed detection sensor. Further, since the belt surface speed detection sensor is often installed only on one side, the trajectory of the endless belt is greatly different in the direction parallel to the axial direction of the transfer roller or the like. Further, when the influence of the axial position deviation and the axial belt tension deviation described above overlaps with the axial deviation of the transfer pressure due to the installation error of the belt surface speed detection sensor, the processing accuracy of each part is improved as in the past. In some cases, it is difficult to suppress the deviation in the axial direction of the transfer pressure within the allowable value.

  Patent Document 1 discloses an invention that is common to the present invention described later in that an adjustment mechanism that adjusts the pressing force of a pressure unit provided at the end of the transfer roller shaft is provided. However, the purpose of providing the pressure means at the end of the transfer roller shaft in the invention of this document is as follows and is different from the object of the present invention. In order to pressurize the transfer roller onto the image carrier such as a photoconductor, the transfer roller shaft is distorted by the pressure applied to both ends of the transfer roller shaft, and the transfer width between the both ends and the center portion is reduced. Deviations may occur. Therefore, in the configuration described in Patent Document 1, the diameter of the transfer roller is formed to be larger at the center than at both ends, and the distance (height) of the transfer roller shaft with respect to the image carrier is changed, so that both ends and the center. Is to suppress the deviation of the transfer width. Further, there is no description or suggestion that the transfer pressure axial direction deviation occurs in the transfer pressure of the transfer roller due to the installation error of the belt surface speed detection sensor, which is the subject of the present invention.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress a transfer roller axial deviation of a transfer roller due to an installation error of a belt surface speed detection sensor within a predetermined allowable value. An image forming apparatus is provided.

In order to achieve the above object, the invention described in claim 1 is directed to an image carrier, an endless belt, a transfer roller that contacts the endless belt at a position facing the image carrier, The pressure means for pressing the image bearing member, a plurality of stretching rollers for stretching the endless belt, a tension applying member for applying a predetermined tension to the endless belt, and a belt surface speed of the endless belt. In the image forming apparatus including the belt surface speed detection sensor for detecting, the belt surface speed detection sensor or a sensor holding member for holding the belt surface speed detection sensor is in contact with the endless belt, and the belt surface speed is detected. A pressure adjusting mechanism that adjusts the pressing force of the pressure roller to the pressure roller of the transfer roller either upstream or downstream in the moving direction of the endless belt of the detection sensor. It is characterized in that provided.
The present invention reduces the axial deviation of the transfer pressure due to the axial position deviation, the axial belt tension deviation, and the installation error of the belt surface speed detection sensor by using the pressure adjusting mechanism provided in the pressurizing means. The pressing force of the pressurizing means can be adjusted. Here, as the pressure adjusting mechanism, for example, a mechanism for adjusting the extension of a pressure spring provided for applying a transfer pressure at the end of the transfer roller is applicable.

In the present invention, the pressurizing force of the pressurizing unit can be adjusted so as to reduce the deviation in the axial direction of the transfer pressure using a pressurization adjusting mechanism provided in the pressurizing unit.
Therefore, it is possible to provide an image forming apparatus capable of suppressing the deviation in the transfer pressure axis direction of the transfer roller due to the installation error of the belt surface speed detection sensor within a predetermined allowable value.

1 is an overall schematic diagram of a copier according to an embodiment. FIG. 5 is an explanatory diagram of a polymerization toner used in the embodiment. FIG. 3 is an explanatory diagram illustrating a schematic configuration of an intermediate transfer belt drive control device. Explanatory drawing about the arrangement | positioning state of a scale mark and a scale sensor. Explanatory drawing about the detection of the scale mark by a scale sensor. Explanatory drawing about the relationship between the waveform which waveform-shaped the detection signal of the scale sensor, and the phase difference of a waveform. FIG. 6 is an explanatory diagram about the influence of belt tension on primary transfer pressure. FIG. 3 is a diagram illustrating a positional relationship among a photosensitive member, a primary transfer roller, and a tension roller on the downstream side of the primary transfer roller in the moving direction of the intermediate transfer belt. The perspective explanatory view about the arrangement position of the surface speed detection device. Plane | planar explanatory drawing about the arrangement position of a surface velocity detection apparatus. Explanatory drawing of a surface velocity detection apparatus. Explanatory drawing of the locus | trajectory of an intermediate transfer belt when there is no installation error of a surface speed detection apparatus. Explanatory drawing of the locus | trajectory of an intermediate transfer belt when there exists an installation error of a surface speed detection apparatus. The graph showing the variation of the deviation in the direction of the transfer pressure axis depending on the presence or absence of the surface speed detection device. Explanatory drawing of the pressurization mechanism of the conventional primary transfer roller. FIG. 3 is an explanatory diagram of an adjustment mechanism provided in the pressure mechanism of the primary transfer roller according to the first exemplary embodiment. FIG. 3 is an explanatory diagram of a configuration in which an adjustment mechanism is provided in the primary transfer roller pressure mechanism according to the first exemplary embodiment. FIG. 6 is an explanatory diagram of a configuration in which an adjustment mechanism is provided in the primary transfer roller pressure mechanism according to the second exemplary embodiment. FIG. 10 is an explanatory diagram of an intermediate transfer unit according to Embodiment 3. FIG. 6 is an explanatory diagram of a configuration in which an intermediate transfer unit according to a third exemplary embodiment is detachably attached to a main body frame.

  Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter referred to as a copying machine) that is an image forming apparatus will be described with reference to the drawings. First, an overall outline of the copier 500 of the present embodiment common to the respective examples will be described. Here, FIG. 1 is an overall schematic diagram of the copier 500 according to the present embodiment, FIG. 2 is an explanatory diagram of the polymerized toner used in the present embodiment, and (a) shows the shape factor SF-1. Explanatory drawing, (b) is explanatory drawing of shape factor SF-2. FIG. 3 is an explanatory diagram illustrating a schematic configuration of the drive control device 70 for the intermediate transfer belt 10, and FIG. 4 is an explanatory diagram illustrating an arrangement state of the scale mark M and the scale sensors 6A and 6B. 5A and 5B are explanatory diagrams for the detection of the scale mark M by each scale sensor 6 (6A, 6B). FIG. 5A is a plan view of the scale mark M viewed from above, and FIG. FIG. 3C is a side perspective view showing the configuration of the system and the optical path, and FIG. FIG. 6 is an explanatory diagram of the relationship between a waveform obtained by shaping the detection signal of the scale sensor and the phase difference between the waveforms, where (a) is the detection signal of the scale sensor 6A, and (b) is the detection signal of the scale sensor 6B. (C) shows the respective phase differences.

  The copying machine 500 according to the present embodiment is a so-called intermediate transfer type tandem type image forming apparatus, which employs a dry two-component developing system using a dry two-component developer. The copying machine 500 includes a copying machine main body 100, a paper feed table 200 on which the copying machine main body 100 is placed, a scanner 300 mounted on the copying machine main body 100, and an automatic document feeder 400 mounted on the scanner 300. Yes. The copying machine main body 100 is provided with an intermediate transfer belt 10 as an endless belt in the center. As shown in FIG. 1, the copying machine 500 of the present embodiment is configured such that the intermediate transfer belt 10 is wound around three support rollers 14, 15, 16 and rotated clockwise in FIG. Yes. Further, after the toner image is secondarily transferred onto the sheet as the recording medium between the second support roller 15 and the third support roller 16 among the three support rollers, the remaining image on the intermediate transfer belt 10 is transferred. A belt cleaning device 17 for removing toner is provided.

  Of the three support rollers, an intermediate transfer belt 10 moving direction (hereinafter referred to as a belt moving direction) is placed on the intermediate transfer belt 10 stretched between the first support roller 14 and the second support roller 15. 4, four image forming units 18 of yellow (Y), magenta (M), cyan (C), and black (K) are arranged side by side from the upstream side to constitute a tandem image forming unit 20. . As shown in FIG. 1, an exposure device 21 is provided above the tandem image forming unit 20. On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20. The secondary transfer device 22 is configured by spanning a secondary transfer belt 24 that is an endless belt between two support rollers 23, and is arranged so as to press against the third support roller 16 via the intermediate transfer belt 10. Then, the toner image transferred onto the intermediate transfer belt 10 is transferred to a sheet.

  A fixing device 25 is provided on the left side of the secondary transfer device 22 in FIG. 1 to fix the toner image secondarily transferred onto the sheet onto the sheet. The fixing device 25 is configured to press a pressure roller 27 against a fixing belt 26 that is an endless belt. The secondary transfer device 22 described above also has a sheet conveying function for conveying the sheet after the secondary transfer to the fixing device 25. As the secondary transfer device 22, a non-contact charger may be used. In such a case, it is difficult to provide this sheet conveying function together. Further, below the secondary transfer device 22 and the fixing device 25 configured as described above, a sheet reversing device 28 for reversing the sheet so as to form an image on both sides of the sheet in parallel with the tandem image forming unit 20 described above. It has.

  Next, the copying operation of the copying machine 500 will be described. When making a copy using the copying machine 500, first, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, the automatic document feeder 400 is closed, and the document is pressed by the automatic document feeder 400. When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the contact glass 32. Immediately, the scanner 300 is driven, and the first traveling body 33 and the second traveling body 34 start traveling. After the start of traveling, light from the light source of the first traveling body 33 is reflected by the document on the contact glass 32, and the reflected light is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35 to the reading sensor 36. Guided, the image information of the document is read.

  When a start switch (not shown) is pressed, the support roller 14 is rotated by a drive motor (not shown), the other two support rollers 15 and 16 are driven to rotate, and the intermediate transfer belt 10 is driven to rotate. At the same time, the photoconductors 40 are rotated by the image forming units 18 to form yellow (Y), magenta (M), cyan (C), and black (K) monochromatic images on the photoconductors 40, respectively. . Then, with the rotation of the intermediate transfer belt 10, each single color image is sequentially transferred to form a composite color image on the intermediate transfer belt 10.

  When a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages, and the separation roller 45 Then, the sheets are separated one by one into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the copying machine main body 100, and abutted against the registration roller 49 and stopped. Alternatively, the sheet set on the manual feed tray 51 is fed by rotating the paper feed roller 50, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet.

  After the color image is transferred, the sheet is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and the fixing device 25 applies heat and pressure to fix the color image on the sheet. The conveying destination is switched, the sheet is discharged by the discharge roller 56, and is stacked on the sheet discharge tray 57. Alternatively, the conveyance destination is switched by the switching claw 55, the sheet is conveyed to the sheet reversing device 28, reversed there and led again to the secondary transfer device 22, and after recording a color image on the back surface, the discharge roller 56 The paper is discharged onto the paper discharge tray 57. In addition, the intermediate transfer belt 10 after the color image transfer is removed by the belt cleaning device 17 to remove residual toner remaining on the intermediate transfer belt 10 after the secondary transfer, so that the tandem image forming unit 20 prepares for another image formation.

Here, the intermediate transfer belt 10 is composed of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like in a single layer or a plurality of layers. A conductive material such as black is dispersed, and the volume resistivity is adjusted to be in the range of 10 ⁸ to 10 ¹² Ωcm, and the surface resistivity is adjusted to be in the range of 10 ⁹ to 10 ¹³ Ωcm. If necessary, a release layer may be coated on the surface of the intermediate transfer belt 10. Materials used for the surface coat include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four Fluorine resins such as fluorinated ethylene-hexafluoropropylene copolymer) and PVF (vinyl fluoride) can be used, but are not limited thereto.

  The intermediate transfer belt 10 may be manufactured by a casting method, a centrifugal molding method, or the like, and the surface thereof may be polished if necessary. If the volume resistivity of the intermediate transfer belt 10 exceeds the above-described range, the bias necessary for transfer increases, which increases the power supply cost. Further, since the charging potential of the intermediate transfer belt 10 becomes high and the self-discharge becomes difficult in the transfer process, the transfer paper peeling process, etc., it is necessary to provide a static eliminating means. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays faster, which is advantageous for static elimination by self-discharge, but the toner scatters because the current during transfer flows in the surface direction. Will occur. Therefore, the volume resistivity and the surface resistivity of the intermediate transfer belt 10 in this embodiment must be within the above ranges. Here, the volume resistivity and surface resistivity were measured by connecting an HRS probe (inner electrode diameter: 5.9 mm, ring electrode inner diameter: 11 mm) to a high resistivity meter (Mitsubishi Chemical Corporation: Hiresta IP) A measured value 10 seconds after applying a voltage of 100 V (surface resistivity of 500 V) to the front and back of the transfer belt 10 was used.

  Each transfer roller 62 is obtained by applying a foamed resin agent to a metal core (iron, SUS, AI, etc.). The thickness of the foamed resin agent is 2 mm to 10 mm, but is not limited thereto.

Next, the toner used in this embodiment will be described. The toner has a shape factor SF-1 in the range of 100 to 180, and a shape factor SF-2 in the range of 100 to 180. 2A is a diagram schematically illustrating the shape of the toner in order to explain the shape factor SF-1, and FIG. 2B is a diagram illustrating the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

  Specifically, each shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX3: manufactured by Nireco) for analysis. Calculated. When the shape of the toner is close to a sphere, the contact state between the toner and the toner or between the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity becomes high. In addition, the attractive force between the toner and the photoreceptor is weakened, and the transfer rate is increased. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered and the cleaning property when attached to the transfer means is also lowered, which is not preferable. The toner particle size is preferably in the range of 4 to 10 μm in terms of volume average particle size. When the particle size is smaller than this, it becomes a cause of background stains during development, fluidity is deteriorated, and further, it tends to agglomerate. On the other hand, when the particle diameter is larger than this, high-definition images cannot be obtained due to toner scattering and resolution deterioration. In this embodiment, a toner having a volume average particle diameter of 6.5 μm is used.

  Next, the rotational drive by the drive control device 70 of the intermediate transfer belt 10 will be described. As shown in FIG. 3, the intermediate transfer belt 10 is stretched around a driving roller 14 and driven rollers 15 and 16, and is moved in a moving (rotating) direction (a direction indicated by an arrow G in the figure) by one driven roller 15. The tension is added. The intermediate transfer belt 10 is driven by the drive roller 14 and moves at a predetermined speed when the speed reducer 8 attached to the drive roller 14 is rotated by the drive motor 7 with the tension applied.

  Further, the intermediate transfer belt 10 of the present embodiment is provided with a plurality of scale marks M continuously at a predetermined interval (pitch) along the side edge portion of the inner peripheral surface over the entire belt moving direction G. Yes. The plurality of scale marks M are formed at the same length in parallel with each other at the same length, and are arranged at a very small pitch along the belt moving direction G, and are provided on the entire circumference of the intermediate transfer belt 10. ing. The scale 5 of the intermediate transfer belt 10 is configured as a whole. Here, the scale mark M is formed in a scale of a predetermined color and is printed with, for example, ink having a higher reflectance than the surface of the intermediate transfer belt 10. Alternatively, a tape printed with a scale mark M having a reflectance different from the reflectance of the ground is attached over the entire circumference of the intermediate transfer belt 10.

  In contrast, the drive control device 70 that controls the rotational drive of the intermediate transfer belt 10 includes a control device 71, a motor drive circuit 81, and a scale mark sensor that detects the scale mark M (hereinafter referred to as a scale sensor). ) 6A, 6B. The scale sensors 6A and 6B are provided at a slight distance below the position where the scale marks M of the intermediate transfer belt 10 are formed. A plurality of (here, two) scale sensors 6A and 6B are arranged at predetermined intervals along the belt movement direction G of the intermediate transfer belt 10, and each of the scale sensors 6A and 6B sequentially detects the scale mark M on the intermediate transfer belt 10, A detection signal is output to the control device 71. As will be described later, the control device 71 acquires position data or the like for correcting the pitch of the scale mark M from the detection signal, and inputs the target position data to the motor drive circuit 81 to move the intermediate transfer belt 10. Control the speed. As described above, the control device 71 appropriately outputs a signal to the motor drive circuit 81 based on the position information of the intermediate transfer belt 10 detected by the scale sensors 6A and 6B, and drives the drive motor 7 by the motor drive circuit 81. Thus, the moving speed of the intermediate transfer belt 10 is feedback controlled.

  Further, as shown in FIG. 4, the scale sensors 6A and 6B are arranged such that one scale sensor 6B is disposed upstream and the other scale sensor 6A is disposed downstream along the belt moving direction G of the intermediate transfer belt 10. The scale mark M is arranged so as to be detectable. Further, the scale sensors 6A and 6B have an interval D between these detection points where an integer multiple of P0 (D = N × P0 (N = 1, 2, 3) when the design value of the pitch of the scale mark M is P0. ...)). When the intermediate transfer belt 10 is not expanded or contracted, it passes through the central portion of the scale mark M at the same time. When the intermediate transfer belt 10 moves, the scale sensors 6 </ b> A and 6 </ b> B sequentially detect the scale marks M and output detection signals to the control device 71. Then, as will be described later, the control device 71 feedback-controls the motor drive circuit 81 based on the phase difference of the detection signal (input signal) or the like.

  The scale mark M is a reflection type mark, and as shown in FIG. 5A, a reflection portion (scale mark M) and a light shielding portion S along the belt moving direction G on the inner peripheral surface of the intermediate transfer belt 10. And are formed alternately. On the other hand, as shown in FIGS. 5B and 5C, the scale sensor 6 has a light receiving window 124 including a light emitting element 121 such as an LED, a collimating lens 122, a slit mask 123, and a transparent cover such as glass or a transparent resin film. And a light receiving element 125 such as a phototransistor, which are fixed to each part of the sensor housing 120.

  When the light emitting element 121 which is the light source of the scale sensor 6 emits light, the light passes through the collimating lens 122 to become a parallel light beam, passes through a plurality of slits 123a parallel to the scale mark M of the slit mask 123, and a plurality of light beams. Divided into LB, the scale 5 on the intermediate transfer belt 10 is irradiated. A part of the plurality of light beams LB is reflected by the scale mark M, the reflected light is received by the light receiving element 125 through the light receiving window 124, and the light receiving element 125 detects the change (strength) of the brightness of the reflected light as an electric signal. Convert to In this way, the scale sensor 6 detects the scale mark M by detecting the intensity of the reflected light by the light receiving element 125, and the presence or absence of the scale mark M accompanying the movement of the intermediate transfer belt 10 is continuously modulated to the analog. Output as an alternating signal. Here, the surface of the slit mask 123 formed with a plurality of slits 123a and the light receiving window 124 facing the scale 5 is on the same plane as the sensor surface 126 facing the scale 5 of the sensor unit housing 120. It is configured.

  Each detection signal detected by the scale sensors 6A and 6B becomes a rectangular pulse signal as shown in FIGS. 6A and 6B. In the scale sensor 6A (FIG. 6A), Ca (1 ), Ca (2), Ca (n), and the scale sensor 6B (FIG. 6 (b)) has waveforms of Cb (1), Cb (2), Cb (n). , Respectively. Here, if the pitch of the scale mark M remains at the design value (initial value) P0 and the distance D between the two scale sensors 6A and 6B is exactly N × P0, the rise and rise of the waveforms of these detection signals. All of the falling timings coincide with each other, and there is no phase difference Cab (Cab = 0). However, in the copying machine 500, the intermediate transfer belt 10 expands and contracts due to the ambient temperature and humidity of the intermediate transfer belt 10 or acting tension, and the position of the scale mark M in the scale 5 varies and fluctuates. As a result, as shown in FIG. 6 (c), a pitch error occurs in the scale mark M, and the rising and falling timings of the pulse waveforms of the scale sensors 6A and 6B are shifted to each other, and the phase difference between them. Cab is produced. The waveform of the phase difference of the detection signal becomes a rectangular pulse signal due to the phase differences Cab (1), Cab (2), and Cab (n) generated according to the difference in waveform of the scale sensors 6A and 6B.

  In the present embodiment, the phase difference Cab of each detection signal is sequentially calculated, and the driving of the intermediate transfer belt 10 is controlled while correcting so as to cancel out the fluctuation or the like according to the calculated phase difference Cab. At this time, for example, an arbitrary pulse phase difference is calculated from each cycle Ca (n), Cb (n) of the detection signal by (ΣCa (n) −ΣCb (n)). However, since Cab (n) includes the initial time difference Cab (1), (Cab (n) −Cab (1)) = (ΣCa (n) −ΣCb (n)) is the pulse phase difference. Here, since both scale sensors 6A and 6B are arranged at intervals of 180 pulses, the correction value for one pulse is obtained by dividing the pulse phase difference by 180 {− (Cab (n) −Cab (1)) / 180}. Accordingly, the corrected value is calculated by Ch (n) = {Ca (n) − (Cab (n) −Cab (1)) / 180}.

  In this way, the control device 71 calculates the correction data of the scale mark pitch, and feeds back the motor drive circuit 81 based on the phase difference sequentially calculated between the correction data and the scale mark M, the measurement result of each period, and the like. And the moving speed of the intermediate transfer belt 10 is controlled. The moving speed and position of the intermediate transfer belt 10 are feedback-controlled while correcting the target position data such as the image transfer position of the intermediate transfer belt 10. Alternatively, the control device 71 creates a pitch error profile of the scale mark M to calculate correction data of the scale mark pitch (pitch error), and determines the moving speed of the intermediate transfer belt 10 from the detection result of the scale mark M. Detect (calculate). Based on the moving speed and the correction data, for example, by controlling the moving speed of the intermediate transfer belt 10 so as to cancel the detected pitch error of each scale mark M, the intermediate position is corrected while correcting the target position data as described above. The moving speed of the transfer belt 10 is feedback-controlled. In the copying machine 500, a reference mark (0 point mark) serving as a reference for one rotation of the intermediate transfer belt 10 is provided in the plurality of scale marks M of the intermediate transfer belt 10. Then, this reference mark is detected by the reference mark detection means to determine that the intermediate transfer belt 10 has made a full turn, and is used for control by the control device 71.

  Next, the axial deviation of the transfer pressure in the direction parallel to the axial direction of the transfer roller or the like in the primary transfer portion of the intermediate transfer belt 10, which is a characteristic portion of the present embodiment, that is, the transfer pressure shaft in the primary transfer portion. A configuration for suppressing the direction deviation will be described with reference to a plurality of examples. Here, each image forming unit 18 that forms the primary transfer portion and the basic configuration around the primary transfer roller are substantially the same, and therefore, the color corresponding to the member is identified by a symbol. Unless necessary, symbols Y, M, C, and K are omitted.

Example 1
First, Example 1 which is a first example of the present embodiment will be described with reference to the drawings. FIG. 7 is an explanatory view of the influence of belt tension on the primary transfer pressure. FIG. 8 is a downstream side in the belt movement direction of the intermediate transfer belt 10 of the photoreceptor 40, the primary transfer roller 62, and the primary transfer roller 62. It is explanatory drawing about the positional relationship of the tension roller. FIG. 9 is an explanatory perspective view of the arrangement position of the surface velocity detection device 110, and FIG. 10 is an explanatory plan view of the arrangement position of the surface velocity detection device 110, and is a perspective view of the subframe 151. 11A and 11B are explanatory views of the surface speed detection device 110, where FIG. 11A is an explanatory view of a state in which the surface speed detection device 110 sandwiches the intermediate transfer belt 10, and FIG. 11B is an explanatory view of the pressing member 135. ) Is an explanatory view of a state in which the sensor substrate 127 is held on the sensor holding member 130, and (d) is an explanatory view of the sensor substrate 127 in which the scale sensors 6A and 6B are integrally provided. FIG. 12 is an explanatory diagram of the locus of the intermediate transfer belt 10 when there is no installation error of the surface speed detection device 110, and FIG. 13 is a locus of the intermediate transfer belt 10 when there is an installation error of the surface velocity detection device 110. It is explanatory drawing of. FIG. 14 is a graph showing variations in deviation in the transfer pressure axis direction depending on the presence / absence of the surface speed detection device 110, and FIG. 15 is an explanatory diagram of the pressure mechanism 140 of the conventional primary transfer roller 62. FIG. 16 is an explanatory diagram of the adjustment mechanism 160 provided in the pressure mechanism 140 of the primary transfer roller 62K of the present embodiment, and (a) is a perspective view from the axial center side of the primary transfer roller 62K. ) Is a perspective view from the outside of the side plate of the sub-frame 151. FIG. 17 is an explanatory diagram of a configuration in which the adjustment mechanism 160 is provided in the pressure mechanism 140 of the primary transfer roller 62K of the present embodiment, where (a) is a perspective view and (b) is a plan view.

  In the copying machine 500 of the present embodiment, each primary transfer roller 62 is an example of a primary transfer unit including a photoreceptor 40K of the image forming unit 18K and a primary transfer roller 62K shown in FIG. Are offset with respect to the respective photoconductors 40 facing each other. More specifically, the rotation center of the primary transfer roller 62 is offset from the rotation center of the photoconductor 40 so as to be on the downstream side in the belt movement direction of the intermediate transfer belt 10 to be sandwiched. This is to suppress abnormal discharge that is likely to occur in the primary transfer portion. As is well known, the discharge depends on the voltage and the gap distance according to Paschen's law. Therefore, the primary transfer roller 62 is offset from the photoconductor 40, and the distance between the transfer nip formed by the intermediate transfer belt 10 and the photoconductor 40 is shortened to suppress the occurrence of discharge. It is to do.

  When the primary transfer roller 62 is offset with respect to each photoconductor 40 in this way, the first transfer roller 62 applies a pressure that causes the photoconductor 40 to generate a primary transfer pressure at the transfer nip portion via the intermediate transfer belt 10. The pressure F acts as shown in FIG. At both ends of the one transfer roller 62, a pressurizing mechanism 140 that is a pressurizing unit that pressurizes the one transfer roller 62 toward the photoconductor 40 is provided, and is directed toward the photoconductor 40 so as to generate a predetermined primary transfer pressure. Pressurized. Here, the pressure mechanism 140 rotatably supports the primary transfer roller 62, and rotates the pressure arm 141 that rotates about the pressure arm rotation support member 142 and the pressure arm 141. It is mainly composed of a spring 143. When a force f1 is applied by the springs 143 at both ends of the first transfer roller 62, a straight line connecting the rotation center of the photoreceptor 40 and the primary transfer roller 62 to the primary transfer roller 62 through the pressure arm 141. The force f2 that is parallel to and toward the photosensitive member 40 acts.

  However, since the primary transfer roller 62 and the like have their own weight, the angle formed by the straight line connecting the photosensitive body 40 and the rotation center of the primary transfer roller 62 and the vertical straight line is θ0. That is, if the mass is m, a force of f3 = m × g (gravity acceleration) × COSθ0 acts in the opposite direction to f2. Further, a predetermined tension T is applied to the intermediate transfer belt 10 by the driven roller 15 functioning as a tension roller, and transfer is performed with the primary transfer roller 62 being offset with respect to the photoreceptor 40 as described above. A nip is formed. Therefore, the angle formed by the locus of the straight line portion of the intermediate transfer belt 10 upstream of the transfer nip portion and the straight line connecting the rotation center of the photosensitive member 40 and the primary transfer roller 62 is θ1, which is not 90 degrees. A force of f4 = T × COSθ1 toward the photoconductor 40 side works. In addition, the angle formed by the locus of the straight line portion of the intermediate transfer belt 10 on the downstream side of the transfer nip portion and the straight line connecting the rotation center of the photosensitive member 40 and the primary transfer roller 62 is θ2, which is not 90 degrees. A force of f5 = T × COSθ1 acting toward the next transfer roller is applied.

  As a result, the applied pressure F for generating the primary transfer pressure is f3 generated by the self-weight of the primary transfer roller 62 and the like f2 applied via the pressure arm 141 by the springs 143 at both ends of the primary transfer roller 62. The resultant force (vector amount: F = f2 + f3 + f4 + f5) with f4 generated by the tension T of the intermediate transfer belt 10 upstream of the transfer nip portion and f5 generated by the tension T of the intermediate transfer belt 10 downstream. In contrast, the primary transfer roller 62 is not offset, and the locus of the linear portion of the intermediate transfer belt 10 upstream and downstream of the transfer nip portion is connected to the rotation center of the photosensitive member 40 and the primary transfer roller 62. When the angle formed by the straight line is 90 degrees, the pressure F that generates the primary transfer pressure is as follows. Neither f4 nor f5 due to the tension T of the intermediate transfer belt 10 occurs, and the applied pressure F that generates the primary transfer pressure is f2 that is the force applied by the spring 143 via the pressure arm 141. The resultant force (vector amount: F = f2 + f3) with f3 generated by the weight of the primary transfer roller 62 and the like. Therefore, the angle formed by the trajectory of the straight line portion of the intermediate transfer belt on either the upstream side or the downstream side of the transfer nip portion, or both, and the straight line connecting the rotation center of the primary transfer roller 62 is 90 degrees. If not, it can be seen that the belt tension affects the primary transfer pressure.

  Further, for example, as shown in FIG. 8, when the downstream tension roller 154 provided on the downstream side in the belt moving direction of the transfer nip portion moves downward from a predetermined position, the primary tension is not changed even if the belt tension does not change. Affects the transfer pressure. This is because the angle between the locus of the straight line portion of the intermediate transfer belt 10 on the downstream side of the transfer nip portion and the straight line connecting the rotation center of the photosensitive member 40 and the primary transfer roller 62 is θ2, and θ2 ′ (θ2 ′ < This is because f5 changes to θ2) and increases toward the primary transfer roller. Further, when moved upward, the angle formed between the photosensitive member 40 and the straight line connecting the rotation centers of the primary transfer roller 62 changes to θ2 ″ (θ2 <θ2 ″ ≦ 90 °), When θ2 ″ is 90 degrees or less, f5 toward the primary transfer roller side becomes small. When θ2 ″ exceeds 90 degrees (90 ° <θ2 ″ ≦ 180 °), the direction in which f5 acts changes to the photoconductor 40 side and increases as the angle increases. Although not shown, the belt tension changes for the same reason even when the upstream tension roller 153 provided on the upstream side of the transfer nip portion in the belt movement direction moves above and below a predetermined position. If not, it will affect the primary transfer pressure. In other words, if the push-up members of the downstream tension roller 154 or the upstream tension roller 153 on either the downstream side or the upstream side in the belt movement direction of the transfer nip portion vary from a predetermined position, the primary transfer is performed. The pressure will change. Further, the pressure F increases as the locus of the intermediate transfer belt 10 toward the transfer nip portion changes closer to the photoreceptor 40 side than the predetermined locus, and changes so as to approach the primary transfer roller 62 side. It will become smaller.

  When the above-described variation in the belt tension and the position of the push-up member deviates in the axial direction (direction parallel to the axial direction of the primary transfer roller 62 or the photoreceptor 40), the primary transfer pressure axis It will affect the direction deviation. That is, when an axial belt tension deviation or an axial position deviation occurs, the transfer pressure axial deviation is affected. Therefore, conventionally, the accuracy of each part is improved and the support roller 15 has a function of a belt tension roller so that the deviation of the primary transfer pressure in the transfer pressure axial direction is within a predetermined allowable range where no deviation occurs in the image density. I was trying to fit in.

  However, in this embodiment, in order to control the drive of the intermediate transfer belt 10 as described above, the scale sensors 6A and 6B are provided, and the moving speed of the intermediate transfer belt 10 is feedback-controlled. In this embodiment, the scale sensors 6A and 6B are not provided individually, but are provided in the surface speed detection device 110 that sandwiches the intermediate transfer belt 10 on one side in the axial direction as shown in FIG. Since the intermediate transfer belt 10 is sandwiched in this way, when an installation error of the surface speed detection device 110 occurs, the locus of the intermediate transfer belt 10 is a predetermined locus on the upstream side and the downstream side of the surface speed detection device 110 in the belt movement direction. May be off. Further, since the surface speed detection device 110 is installed only on one side of the intermediate transfer belt 10, the locus of the intermediate transfer belt 10 is greatly different in the axial direction.

  In particular, when the distance from the end of the member sandwiching the intermediate transfer belt 10 of the surface speed detection device 110 to the transfer roller is short, the deviation angle from a predetermined locus becomes large, and the influence on the transfer pressure axial deviation is large. turn into. Furthermore, when the influence of the axial position deviation and the axial belt tension deviation described above overlaps with the transfer pressure axial deviation caused by the installation error of the surface speed detection device 110, the processing accuracy of each component is increased as in the conventional case. The possibility of occurrence of a case where it is difficult to suppress the deviation in the axial direction of the transfer pressure within the allowable value by just increasing has been increased. Therefore, in this embodiment, the primary transfer roller 62K that faces the photoconductor 40K via the intermediate transfer belt 10 is applied to the pressurizing mechanism 140 that is a pressurizing unit that pressurizes the photoconductor 40K. An adjustment mechanism 160 that is a pressure adjustment mechanism is provided. Hereinafter, the configuration of the surface velocity detection device 110 and the mechanism that causes the transfer pressure axis direction deviation in the primary transfer portion will be described in more detail, and the adjustment mechanism 160 of the present embodiment will be described.

  As shown in FIGS. 9 and 10, the surface speed detection device 110 of the present embodiment is arranged in the axial direction on a subframe 151 supported by a belt unit frame 150 (not shown) that holds a primary transfer roller 62K. It is attached to one end side. In addition, it is mounted between the primary transfer roller 62K facing the photoconductor 40K and the upstream tension roller 153 provided on the upstream side in the belt moving direction. As described above, the surface speed detection device 110 according to the present embodiment is also arranged on one side near the primary transfer roller 62K, as in a general configuration.

  As shown in FIG. 11A, the surface velocity detection device 110 is mainly composed of a sensor holding member 130 and a belt pressing member 135, and is fixed to one end side of a subframe 151 (not shown) via a sensor bracket 111. Is done. The sensor holding member 130 and the belt pressing member 135 sandwich the portion of the intermediate transfer belt 10 where the scale 5 is formed. Here, as shown in FIG. 11B, the belt pressing member 135 includes a belt pressing frame 136 and a base layer bonded to the belt pressing frame 136 and a sponge belt contact member 137. When the intermediate transfer belt 10 is sandwiched between the sensor holding member 130 and the belt contact member 137, pressure is applied to the intermediate transfer belt 10, and therefore it is preferable to reduce the frictional force of the belt contact portion of the belt contact member 137. . Therefore, the belt contact member 137 of the present embodiment is flocked to reduce the frictional force.

  As shown in FIG. 11C, the sensor holding member 130 holds a sensor substrate 127 (see FIG. 11D) provided with scale sensors 6A and 6B. Two sensor windows 132 for exposing a part of the sensor surface 126 of each scale sensor to the intermediate transfer belt 10 are formed on the belt facing surface 131 of the sensor holding member 130. Further, similar to the belt pressing member 135, the belt facing surface 131 is flocked to reduce the frictional force. On the other hand, the sensor substrate 127 held by the sensor holding member 130 is provided with the scale sensor 6A on the upstream side in the belt moving direction G and the scale sensor 6B on the downstream side as shown in FIG. .

  By configuring the surface speed detection device 110 in this way, fluttering of the intermediate transfer belt 10 is suppressed at the detection position of the scale 5 and accurate speed detection is possible. Here, in this embodiment, the position where the surface speed detection device 110 and the scale 5 are provided is on one end side of the intermediate transfer belt 10. It is because it becomes impossible to install.

  In the description of the arrangement of the surface speed detection device 110 described above, the arrangement on the subframe 151 has been described. However, the arrangement including the photoreceptor 40C and the primary transfer roller 62C on the upstream side in the belt moving direction is illustrated in FIG. The arrangement is as shown in. As shown in FIG. 12, the primary nip portion between the photosensitive member 40C and the primary transfer roller C on the upstream side in the belt moving direction is stretched to the primary nip portion between the downstream photosensitive member 40K and the primary transfer roller 62K. The upstream tension roller 153 and the surface speed detection device 110 are arranged so that the locus of the intermediate transfer belt 10 is as straight as possible. The trajectory of the intermediate transfer belt 10 arranged in this way becomes a target predetermined trajectory. Further, as described above, the surface speed detection device 110 is located between the upstream tension roller 153 and the primary transfer roller 62K, that is, close to the primary transfer roller 62K. This is because the belt moving speed during the primary transfer should be as close as possible when it is desired to achieve a target speed with high accuracy. In addition, when aiming to improve color matching accuracy, it is most preferable to dispose between the primary transfer rollers 62.

  However, when an installation error occurs in the surface velocity detection device 110 provided at one end of the intermediate transfer belt 10, for example, as shown in FIG. Thus, the trajectory of the intermediate transfer belt 10 on the upstream side and the downstream side in the belt moving direction deviates from the predetermined trajectory shown in FIG. For this reason, the locus of the intermediate transfer belt 10 from the primary nip portion between the photoconductor 40C and the primary transfer roller C to the surface speed detection device 110, and one of the photoconductor 40K and the primary transfer roller K from the surface speed detection device 110. The trajectory of the intermediate transfer belt 10 to the next nip portion changes so as to approach each photoconductor 40 side. However, the trajectory of the intermediate transfer belt 10 on the other end side where the surface speed detecting device 110 is not provided is a predetermined trajectory indicated by a one-dot chain line in FIG. Therefore, both the primary nip portion between the photoconductor 40C and the primary transfer roller C and the primary nip portion between the photoconductor 40K and the primary transfer roller K, that is, the front side in FIG. As a result, a transfer pressure axial deviation in which the transfer pressure on the side on which the tape is provided becomes high occurs.

In the configuration of the present embodiment, the distance from the surface speed detection device 110 is closer to the primary nip portion between the photoconductor 40K and the primary transfer roller 62K than the primary nip portion between the photoconductor 40C and the primary transfer roller C. Therefore, the influence is large, and it is difficult to suppress the deviation in the transfer pressure axial direction of the primary nip portion between the photosensitive member 40K and the primary transfer roller K within an allowable value. Therefore, the deviation in the transfer pressure axial direction between the state where the surface speed detector 110 is provided and the state where the surface speed detector 110 is not provided at the primary nip portion between the photosensitive member 40K and the primary transfer roller K was compared. Specifically, the transfer pressure axis direction deviation is calculated in a state in which the surface speed detection device 110 is provided (with sensor: A), and then the surface speed detection device 110 is removed (without sensor: A). Thereafter, the surface velocity detection device 110 was attached and calculated (with sensor: c). And the result like the graph of FIG. 14 was obtained.
Here, the transfer pressure at the side end where the surface speed detection device 110 is provided is defined as the front transfer pressure, and the transfer pressure at the side end where the surface speed detection device 110 is not provided is defined as the rear transfer pressure. (Transfer pressure axis direction deviation) was determined by the following equation (3).
Pressure deviation [%] = (front transfer pressure−rear transfer pressure) / (front transfer pressure + rear transfer pressure) × 100 (3)
As a result, in the configuration of this example, there was a difference of about 5% with and without the surface speed detector 110. However, this is not necessarily 5% because it is determined by variations in the tolerance of each member and assembly.

  As shown in the graph of FIG. 14, when the transfer pressure axis direction deviation of about 5% occurs with or without the surface speed detection device 110, the primary nip portion between the photoconductor 40K and the primary transfer roller K as described above. It was difficult to suppress the deviation in the axial direction of the transfer pressure within an allowable value. Therefore, in this embodiment, the primary transfer roller 62K described with reference to FIG. 7 is adjusted at both ends of the primary transfer roller 62K by adjusting the force f2 that pressurizes the primary transfer roller 62K toward the photoreceptor 40K. The pressure F was adjusted to be equal at both ends of 62K. As a specific method, an adjustment mechanism 160 that is a pressure adjustment mechanism that adjusts the pressure is provided to the pressure mechanisms 140 provided at both ends of the primary transfer roller 62K. Then, the restoring force (f1) of the spring 143 that generates the force (f2) for pressing the primary transfer roller 62K against the photosensitive member 40K is adjusted via the pressure arm 141.

  Conventionally, as shown in FIG. 15, an adjustment mechanism 160 that adjusts the pressing force to the pressing mechanism 140 and adjusts the pressing force F to be equal at both ends of the primary transfer roller 62 has not been provided. . The pressurizing mechanism 140 shown in FIG. 15 is configured as follows. Here, since the pressure mechanisms 140 provided at both ends of the primary transfer roller 62 are symmetrical with respect to the central portion in the axial direction of the primary transfer roller 62, the front side (hereinafter referred to as the front side) in FIG. Will be described. A pressure arm 141 that holds the primary transfer roller 62 rotatably and pressurizes the primary transfer roller 62 toward the photoconductor 40 is rotated by a pressure arm rotation support member 142 on a side plate of the subframe 151. Supported as possible. The pressure arm 141 is formed in a substantially L shape, and a support portion of the primary transfer roller 62K is formed at an end portion on the long side, and an end portion on a short side that is bent downward on the upstream side in the belt moving direction. A mounting hook 144 that supports one end of the spring 143 is formed. A spring hook member 145 having a columnar mounting groove and supporting the other end of the spring 143 is fixed to the side plate of the subframe 151 on the upstream side in the belt movement direction of the mounting hook 144.

  In FIG. 15, the spring 143 has been removed so that the shape of the mounting hook 144 can be easily understood, but one end of the spring 143 is attached to the mounting hook 144 during assembly. The pressurizing mechanism 140 configured in this way has a force in the direction of rotating the pressurizing arm 141 by the restoring force (f1) of the spring 143 supported so as to extend to the spring hooking member 145 and the attachment hook 144. Work. Then, the primary transfer roller 62 is directed toward the photoreceptor 40 and is pressurized with a predetermined pressure (f2). Here, the spring constant of the spring 143 is 0.4 N / mm in this example, but it is not limited to this because it differs for each layout. In general, the smaller the fluctuation of the applied pressure with respect to the position fluctuation, the better. It is advantageous that the spring constant of the spring is low. Thus, conventionally, the spring hooking member 145 is fixed to the side plate of the subframe 151, and the restoring force of the spring 143, that is, the initial amount of extension of the spring 143 is constant.

  Therefore, the adjustment mechanism 160 of the present embodiment is configured to be able to adjust the restoring force (f1) of the spring 143, that is, the initial amount of extension of the spring 143. Specifically, as shown in FIGS. 16A and 16B, the spring hook member 145, which has been fixed in the past, is fixed to an adjustment plate 161 which is a separate component from the side plate of the subframe 151, and this adjustment is performed. The plate 161 is configured to be rotatable with respect to the side plate of the subframe 151 and fixed with screws. The adjustment plate 161 has a substantially elliptical shape, and a hole into which the adjustment plate attachment screw 162 is screwed is provided at the center thereof, and a spring hook member 145 is fixed to an inner portion of the subframe 151 below the hole. ing. In addition, an arc-shaped opening 163 is formed in the side plate of the subframe 151 so that the spring hook member 145 fixed to the adjustment plate 161 can rotate about the adjustment plate mounting screw 162.

  Then, the adjustment plate 161 is screwed to the side plate of the subframe 151 from the outside with a leveling plate mounting screw 162 so that the spring hook member 145 is fitted into the opening 163. Further, an adjustment scale 164 is provided on the upper portion of the adjustment plate 161, and a mark serving as a reference for the scale is applied to a corresponding position outside the side plate of the subframe 151. In practice, the adjustment mechanism 160 provided at both ends is adjusted while measuring the transfer pressure in the vicinity of both ends, so that no scale is required, but this is a guideline for initial assembly before adjustment. Here, in FIG. 16A, the spring 143 is removed for the same reason as in FIG. 15, but one end of the spring 143 is attached to the attachment hook 144 at the time of assembly. Also, the spring constant of the spring 143 is set to 0.4 N / mm in this embodiment, as in the conventional example, but is not limited to this because it varies from layout to layout.

  By configuring the adjustment mechanism 160 in this manner, the initial extension amount of the spring 143 can be adjusted by rotating the adjustment plate 161 during initial assembly or when adjusting the primary transfer pressure. That is, the restoring force (f1) of the spring 143 that generates the force (f2) for pressing the primary transfer roller 62K against the photoconductor 40K by the spring 143 can be adjusted. Accordingly, the force (f2) for pressing the primary transfer roller 62K against the photoconductor 40K by the spring 143, the force (f4, f5) caused by the movement of the intermediate transfer belt 10 from the predetermined locus, and the primary transfer roller The applied force F (f2 + f3 + f4 + f5), which is the resultant force of 62K's own weight (f3), can be adjusted. Therefore, it is possible to provide an image forming apparatus that can suppress the deviation in the transfer pressure axial direction of the primary transfer roller 62K due to the installation error of the surface speed detection device 110 within a predetermined allowable value.

  In this embodiment, as shown in FIGS. 17A and 17B, the pressure mechanism 140 is provided at both ends (front end and rear end) of the primary transfer roller 62K. Therefore, f1 to f5 and the applied pressure F are equivalent to the force applied to each end and the force borne at each end, respectively. In this embodiment, since the pressure mechanism 140 is provided at both ends (front end and rear end) of the primary transfer roller 62K, for example, the surface speed detection device 110 installed on the front side includes: As shown in FIG. 13, when it is installed in a state of moving upward, the following adjustment is performed. When none of the adjusting mechanisms 160 is adjusted, the front pressurizing force F ′ is larger than the rear pressurizing force F ″. Therefore, the adjustment plate 161 is rotated to the upstream side in the belt movement direction by the adjustment mechanism 160 on the front side, and the adjustment plate 161 is rotated to the downstream side in the belt movement direction by the adjustment mechanism 160 on the rear side. That is, the initial extension amount of the spring 143 is reduced by the front adjustment mechanism 160 and the initial extension amount of the spring 143 is increased by the front adjustment mechanism 160, and the pressure F is applied to both ends of the primary transfer roller 62. Are adjusted to be equal. In this way, by adjusting the adjusting mechanism 160 at both ends of the primary transfer roller 62K, the primary transfer pressure can be set to a predetermined value even when the crossing of each member is large and the transfer pressure axial deviation is large. The deviation can be suppressed without greatly deviating from the primary transfer pressure.

  Further, in this embodiment, in order to suppress a deviation in the transfer pressure axial direction of the primary nip portion between the photoconductor 40K and the primary transfer roller 62K on the side closer to the surface speed detection device 110, the pressurization of the primary transfer roller 62K is performed. Only the mechanism 140 is provided with the adjusting mechanism 160. That is, the adjustment mechanism 160 is provided only in the pressure mechanism 140 of the primary transfer roller 62K on the downstream side in the belt movement direction of the surface speed detection device 110. However, the present invention is not limited to such a configuration, and the provision of the adjustment mechanism 160 in the pressure mechanism 140 of the primary transfer roller 62C on the upstream side in the belt movement direction of the surface speed detection device 110 is prevented. is not. For example, the adjustment mechanism 160 may be provided in the pressure mechanisms 140 of both the primary transfer roller 62C on the upstream side in the belt movement direction of the surface speed detection device 110 and the primary transfer roller 62K on the downstream side. Thus, by providing the adjustment mechanism 160 in both the pressure mechanisms 140, it is possible to suppress the transfer pressure axial deviation of the primary transfer roller 62 on both sides of the surface speed detection device 110. Further, when the distance from the nip portion between the photoreceptor 40C upstream of the belt conveyance direction and the primary transfer roller 62C to the surface speed detection device 110 is short, it is necessary to suppress only the deviation in the transfer pressure axis direction. The adjustment mechanism 160 may be provided only in the pressure mechanism 140 of the primary transfer roller 62C. That is, the adjustment mechanism 160 may be provided in the pressure mechanism 140 of the primary transfer roller 62 that needs to suppress the deviation in the transfer pressure axis direction depending on the apparatus configuration.

(Example 2)
Next, Example 2 which is a second example of the present embodiment will be described with reference to the drawings. The present embodiment is different from the above-described first embodiment only in the following points. In the first embodiment, the adjustment mechanism 160 is provided on the pressure mechanisms 140 at both ends of the primary transfer roller 62K, whereas in this embodiment, adjustment is performed only on the pressure mechanism 140 on one side of the primary transfer roller 62K. This is a point related to the provision of the mechanism 160. Since the other points are the same as in the first embodiment, the same configuration, operation and effect will be omitted as appropriate. 18A and 18B are explanatory views of a configuration in which the adjustment mechanism 160 is provided in the pressure mechanism 140 of the primary transfer roller 62K of the present embodiment, where FIG. 18A is a perspective view and FIG. 18B is a plan view.

  As shown in FIGS. 18A and 18B, in this embodiment, unlike the first embodiment, the adjustment mechanism 160 is provided only in the pressure mechanism 140 of the primary transfer roller 62K. More specifically, the adjustment mechanism 160 is provided only in the pressure mechanism 140 on the front side of the primary transfer roller 62K. With this configuration, the adjusted primary transfer pressure deviates from a predetermined primary transfer pressure as compared with the configuration in which the adjustment mechanism 160 is provided in the pressure mechanisms 140 on both sides as in the first embodiment. Even if only one side of the pressure mechanism 140 of the next transfer roller 62K is adjusted, the deviation in the direction of the transfer pressure axis can be reduced, and there is an effect that the trouble of adjusting the adjustment mechanisms 160 on both sides can be saved. That is, as in the case of the copying machine 500 of the present embodiment, an intermediate transfer type tandem type image forming apparatus having a plurality of primary transfer rollers 62 and a surface speed detecting device 110 between them, There is an effect of reducing the deviation in the transfer pressure axis direction of the primary transfer roller 62 on both sides of the surface speed detection device 110. Furthermore, the cost can be reduced as compared with the case where the adjustment mechanisms 160 are provided on both sides.

  The surface speed detection device 110 is also arranged on the same front side as the side on which the adjustment mechanism 160 is provided. By arranging in this way, the side where the scale sensors 6A and 6B provided in the surface speed detection device 110 are located often deviates from the target transfer pressure, but the effect of adjusting the target transfer pressure to reduce the pressure deviation is effective. is there.

(Example 3)
Next, Example 3 which is a third example of the present embodiment will be described with reference to the drawings. The present embodiment differs from the first and second embodiments described above only in the following points. In this embodiment, the transfer unit 170 including the intermediate transfer belt 10, each transfer roller 62, the surface speed detection device 110, the pressure mechanism 140, the adjustment mechanism 160, and the like is slidable with respect to the apparatus main body. It is a point related to that it stipulates. Since the other points are the same as those in the first and second embodiments, the same configuration, operation, and effect will be omitted as appropriate. FIG. 19 is an explanatory diagram of the intermediate transfer unit 170 of the present embodiment, and FIG. 20 is an explanatory diagram of a configuration in which the intermediate transfer unit 170 of the present embodiment is detachably attached to the main body frame.

  As shown in FIG. 19, the transfer unit 170 of this embodiment includes each primary transfer roller 62 including a primary transfer roller 62 </ b> K in which an adjustment mechanism 160 is provided in the intermediate transfer belt 10 and the pressure mechanism 140. . Also provided are a plurality of stretching rollers such as an upstream stretching roller 153 and a downstream stretching roller 154, a support roller 15 functioning as a tension roller, a surface speed detection device 110, a pressure mechanism 140, and an adjustment mechanism 160. ing. As shown in FIG. 20, the transfer unit 170 is connected to the main body frame 180 by an upstream slide rail 171 provided on the upstream side in the belt movement direction and a downstream slide rail 172 provided on the downstream side. It is detachable by sliding in the front-rear direction. An adjustment mechanism 160 that adjusts the pressure applied by the pressure mechanism 140 of the primary transfer roller 62K and a surface speed detection device 110 are provided on the front side in the direction of removal from the apparatus main body.

As described above, the attachment / detachment method is the front / rear slide method, and the adjustment mechanism 160 is on the front side in the direction of detachment from the apparatus main body. effective.
The surface speed detection device 110 is also arranged on the same front side as the side on which the adjustment mechanism 160 is provided. By arranging in this way, the adjustment mechanism 160 can be adjusted in the state of being mounted on the apparatus main body, so that labor can be saved, and the side where the scale sensors 6A and 6B provided in the surface speed detection device 110 are present is aimed. Although it often deviates from the transfer pressure, there is an effect of reducing the pressure deviation by adjusting to the target transfer pressure.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
An image carrier such as a photoreceptor 40K, an endless belt such as an intermediate transfer belt 10, a transfer roller such as a primary transfer roller 62K that contacts the endless belt at a position facing the image carrier, and the transfer roller. The pressure means such as a pressure mechanism 140 that pressurizes the image carrier, a plurality of tension rollers such as an upstream tension roller 153 and a downstream tension roller 154 that tension the endless belt; A tension applying member such as a support roller 15 that functions as a tension roller that applies a predetermined tension to the endless belt, and a belt such as scale sensors 6A and 6B provided in the surface speed detection device 110 that detects the belt surface speed of the endless belt. In an image forming apparatus such as a copying machine 500 provided with a surface speed detection sensor, the belt surface speed detection sensor or the belt surface speed detection sensor A sensor holding member such as a sensor holding member 130 that holds the belt is in contact with the endless belt, and either or both of the transfer rollers on the upstream side and the downstream side in the moving direction of the endless belt of the belt surface speed detection sensor The pressurizing means is provided with a pressurizing adjustment mechanism such as an adjusting mechanism 160 for adjusting the pressure applied by the pressurizing means.
According to this, as described in the first embodiment, the transfer roller such as the primary transfer roller 62K caused by the installation error of the belt surface speed detection sensor such as the scale sensors 6A and 6B provided in the surface speed detection device 110. It is possible to provide an image forming apparatus capable of suppressing the deviation in the transfer pressure axis direction within a predetermined allowable value.
(Aspect B)
In (Aspect A), a plurality of the transfer rollers such as the primary transfer roller 62K and the primary transfer roller 62C are provided, and the belts such as the scale sensors 6A and 6B provided in the surface speed detection device 110 between any of the transfer rollers. A surface speed detection sensor is disposed, and an adjustment mechanism is provided in the pressure means such as the pressure mechanism 140 of the transfer roller upstream and downstream in the moving direction of the endless belt such as the intermediate transfer belt 10 of the belt surface speed detection sensor. The pressure adjusting mechanism such as 160 is provided.
According to this, as described in the first embodiment, pressurization of the transfer rollers such as the primary transfer roller 62K and the primary transfer roller 62C on the upstream side and the downstream side in the moving direction of the endless belt such as the intermediate transfer belt 10 is performed. By providing a pressure adjusting mechanism such as the adjusting mechanism 160 in the pressure means such as the mechanism 140, the transfer rollers on both sides of the belt surface speed detection sensor such as the scale sensors 6A and 6B provided in the surface speed detection device 110 are provided. The deviation in the transfer pressure axis direction can be suppressed.
(Aspect C)
In (Aspect A) or (Aspect B), the pressure adjustment mechanism such as the adjustment mechanism 160 is provided only at one end of the transfer roller such as the primary transfer roller 62K or the primary transfer roller 62C. It is a feature.
According to this, as described in the second embodiment, the transfer pressure axial deviation can be reduced by adjusting only one side of the pressure unit such as the pressure mechanism 140 of the transfer roller such as the primary transfer roller 62K. Therefore, it is possible to save the trouble of adjusting the pressure adjusting mechanism such as the adjusting mechanism 160 on both sides.
(Aspect D)
In (Aspect C), the belt surface speed detection sensor such as the scale sensors 6A and 6B provided in the surface speed detection device 110 and the pressure adjustment mechanism such as the adjustment mechanism 160 are connected to the primary transfer roller 62K or the primary transfer. It is provided on the same side of the transfer roller as the roller 62C.
According to this, as described in the second embodiment, the belt surface speed detection sensors such as the scale sensors 6A and 6B provided in the surface speed detection device 110 are the same as the side where the pressure adjustment mechanism such as the adjustment mechanism 160 is provided. Since it is arranged on the front side, the side where the belt surface speed detection sensor is located often deviates from the target transfer pressure, but there is an effect of adjusting the target transfer pressure to reduce the pressure deviation.
(Aspect E)
An image carrier such as a photoreceptor 40K, an endless belt such as an intermediate transfer belt 10, a transfer roller such as a primary transfer roller 62K that contacts the endless belt at a position facing the image carrier, and the transfer roller. The pressure means such as a pressure mechanism 140 that pressurizes the image carrier, a plurality of tension rollers such as an upstream tension roller 153 and a downstream tension roller 154 that tension the endless belt; A tension applying member such as a support roller 15 that functions as a tension roller that applies a predetermined tension to the endless belt, and a belt such as scale sensors 6A and 6B provided in the surface speed detection device 110 that detects the belt surface speed of the endless belt. In an image forming apparatus such as a copying machine 500 provided with a surface speed detection sensor, the belt surface speed detection sensor or the belt surface speed detection sensor A sensor holding member such as a sensor holding member 130 that holds the belt is in contact with the endless belt, and either or both of the transfer rollers on the upstream side and the downstream side in the moving direction of the endless belt of the belt surface speed detection sensor The pressure adjusting means is provided with a pressure adjusting mechanism such as an adjusting mechanism 160 for adjusting the pressure applied by the pressure means, and the endless belt, the transfer roller, the plurality of tension rollers, the tension applying member, and the belt. A transfer unit, such as a transfer unit 170, which includes a surface speed detection sensor, the pressurizing means, and the pressurization adjusting mechanism and can be attached and detached by sliding back and forth with respect to the apparatus main body, is removed from the apparatus main body. The pressurizing adjustment mechanism is provided in the main body.
According to this, as described in the third embodiment, the attachment / detachment method is the front / rear slide method, and the pressure adjustment mechanism such as the adjustment mechanism 160 is on the front side in the removal direction from the apparatus main body. The transfer unit can be adjusted in a state where the transfer unit is mounted on the apparatus main body.
(Aspect F)
In (Embodiment E), in addition to the pressure adjusting mechanism such as the adjusting mechanism 160 on the side of removing the transfer unit such as the transfer unit 170 from the apparatus main body, the scale sensor 6A provided in the surface speed detecting device 110, The belt surface speed detection sensor such as 6B is also provided.
According to this, as described in the third embodiment, since the pressure adjusting mechanism such as the adjusting mechanism 160 can be adjusted in the state of being mounted on the apparatus main body, labor can be saved and the surface speed detecting device 110 can be saved. Although the side where the belt surface speed detection sensor such as the scale sensors 6A and 6B provided on the surface is deviated from the target transfer pressure, the pressure deviation is reduced by adjusting the target transfer pressure.

5 Scale 6A, 6B Scale sensor 7 Drive motor 8 Reducer 10 Intermediate transfer belt 10
14 Support roller (drive roller)
15 Support roller (driven roller, tension roller)
16 Support roller (driven roller)
DESCRIPTION OF SYMBOLS 17 Belt cleaning apparatus 18 Image forming means 20 Tandem image forming part 21 Exposure apparatus 22 Secondary transfer apparatus 23 Support roller (secondary transfer belt)
24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Sheet reversing device 30 Document table 32 Contact glass 33 First traveling member 34 Second traveling member 35 Imaging lens 36 Reading sensor 40 Photosensitive member 42, 50 Paper feed Roller 43 Paper bank 44 Paper feed cassette 45, 52 Separation roller 46, 48, 53 Paper feed path 47 Transport roller 49 Registration roller 51 Tray 55 Switching claw 56 Ejection roller 57 Ejection tray 62 Primary transfer roller 70 Drive controller 71 Control Device 81 Motor drive circuit 100 Copier body 110 Surface speed detection device 111 Sensor bracket 120 Sensor housing 121 Light emitting element 122 Collimating lens 123 Slit mask 123a Slit 124 Light receiving window 125 Light receiving element 126 Sensor surface 127 Substrate 130 Sensor holding member 131 Belt facing surface 132 Sensor window 135 Belt pressing member 136 Belt pressing frame 137 Belt contact member 140 Pressure mechanism 141 Pressure arm 142 Pressure arm rotation support member 143 Spring 144 Mounting hook 145 Spring hooking member 150 Belt unit frame 151 Sub frame 153 Upstream tension roller 154 Downstream tension roller 160 Adjustment mechanism 161 Adjustment plate 162 Adjustment plate mounting screw 163 Adjustment opening 164 Adjustment scale 170 Intermediate transfer unit 180 Main frame 200 Paper feed table 300 Scanner 400 Automatic document feeder LB Light beam M Scale mark

JP 2009-025473 A

Claims (6)

An image carrier, an endless belt, a transfer roller that contacts the endless belt at a position facing the image carrier, the pressure unit that presses the transfer roller toward the image carrier, and the endless belt. In an image forming apparatus comprising: a plurality of stretching rollers for stretching; a tension applying member that applies a predetermined tension to the endless belt; and a belt surface speed detection sensor that detects a belt surface speed of the endless belt.
The belt surface speed detection sensor or a sensor holding member that holds the belt surface speed detection sensor is in contact with the endless belt,
A pressure adjusting mechanism that adjusts the pressing force of the pressure roller is provided on the pressure roller of the transfer roller on either the upstream side or the downstream side in the moving direction of the endless belt of the belt surface speed detection sensor. An image forming apparatus. The image forming apparatus according to claim 1.
A plurality of the transfer rollers are provided, and the belt surface speed detection sensor is disposed between any of the transfer rollers,
An image forming apparatus according to claim 1, wherein the pressure adjusting mechanism is provided in the pressure means of the transfer roller upstream and downstream in the moving direction of the endless belt of the belt surface speed detection sensor. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the pressure adjusting mechanism is provided only at one end of the transfer roller. The image forming apparatus according to claim 3.
An image forming apparatus, wherein the belt surface speed detection sensor and the pressure adjusting mechanism are provided on the same side of the transfer roller. An image carrier, an endless belt, a transfer roller that contacts the endless belt at a position facing the image carrier, the pressure unit that presses the transfer roller toward the image carrier, and the endless belt. In an image forming apparatus comprising: a plurality of stretching rollers for stretching; a tension applying member that applies a predetermined tension to the endless belt; and a belt surface speed detection sensor that detects a belt surface speed of the endless belt.
The belt surface speed detection sensor or a sensor holding member that holds the belt surface speed detection sensor is in contact with the endless belt,
A pressure adjusting mechanism that adjusts the pressing force of the pressure roller is provided on the pressure roller of the transfer roller on either the upstream side or the downstream side in the moving direction of the endless belt of the belt surface speed detection sensor. ,
The endless belt, the transfer roller, the plurality of stretching rollers, the tension applying member, the belt surface speed detection sensor, the pressurizing unit, and the pressure adjusting mechanism, and slides back and forth with respect to the apparatus main body. Of the transfer unit that can be removed by
An image forming apparatus, wherein the pressure adjusting mechanism is provided on the side in the direction of removal from the apparatus main body. The image forming apparatus according to claim 5.
An image forming apparatus comprising: a belt surface speed detection sensor in addition to the pressure adjusting mechanism on a side of removing the transfer unit from the apparatus main body.

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