JP4689162B2 - Belt running stabilization device and image forming apparatus - Google Patents

Description

  The present invention relates to a belt travel stabilization device that eliminates and stabilizes a travel variation such as a variation in transport speed of an endless belt such as an intermediate transfer belt, a photoreceptor belt, and a paper transport belt, and a copier, facsimile, The present invention relates to an image forming apparatus such as a printer and other apparatuses.

  Endless belts are used in various devices. For example, in an image forming apparatus such as a copying machine, a facsimile machine, or a printer, an image carrier such as a photosensitive member, an intermediate transfer member to which an image carried on the image carrier is transferred, a transfer material, transfer paper, or recording paper An endless belt may be used as a conveying member that conveys a recording medium referred to as “etc.”. In an image forming apparatus using such an endless belt, high-precision drive control of the endless belt is important for obtaining a high-quality image.

  That is, for example, as one of such image forming apparatuses, a tandem type color image forming apparatus that is particularly excellent in image forming speed and suitable for downsizing is known. A recording medium is conveyed using a belt, and sequentially passes through a plurality of image forming units that form different monochrome images arranged along the conveying direction, thereby superimposing each monochrome image on the recording medium. In order to obtain a color image, high-precision drive control of the endless belt is essential for forming a high-quality image. This will be described more specifically as follows.

  In such a tandem type color image forming apparatus, for example, image forming units that form single color images of yellow, magenta, cyan, and black are sequentially arranged in the conveyance direction of the recording medium. Each image forming unit is provided with a photosensitive drum as an image carrier for carrying each single color image. A laser exposure unit for forming an electrostatic latent image on each photosensitive drum is disposed in the vicinity of the image forming unit, and the electrostatic latent image formed on the surface of each photosensitive drum by the laser exposure unit is provided. A toner image is formed by developing in the image forming unit.

  A conveying belt which is an endless belt is disposed facing the image forming unit. The conveying belt is stretched between the driving roller and the driven roller arranged in parallel with each other with an appropriate tension. The driving roller is rotationally driven by a motor at a predetermined rotational speed, and accordingly, the conveying belt also rotates at a predetermined speed.

  A paper feed mechanism that supplies the recording medium to the image forming unit side of the transport belt at a predetermined timing is provided. The recording medium sent from the paper feed mechanism is attracted to the transport belt by electrostatic force, and the transport belt moves. By being conveyed at the same speed as the speed, it sequentially passes through the area facing each image forming unit.

During this passage, the toner images formed on the respective photosensitive drums are sequentially superimposed on the recording medium and transferred, and then the toner is melted and pressure-bonded by a fixing device, whereby a color image is formed on the recording medium. It becomes.
Therefore, in such a tandem type color image forming apparatus, it is possible to stabilize the conveyance speed of the recording medium, that is, the movement speed of the conveyance belt, to a predetermined speed. This is extremely important in reducing deviation and forming a high-quality image.

  The stabilization of the moving speed of the endless belt is important when the endless belt is used as an intermediate transfer member or when it is used as an image carrier such as a photoreceptor. For example, when an endless belt is used as an image carrier, unevenness in the moving speed causes density unevenness in a monochromatic image formed on the image carrier, and thus high-precision drive control is required.

As described above, highly accurate drive control for moving an endless belt at a constant moving speed is required. Such a requirement applies not only to the image forming apparatus but also to various apparatuses.
Therefore, conventionally, in order to realize such highly accurate drive control, the cause of fluctuations in the moving speed of the endless belt has been investigated, and various techniques for measuring the moving speed of the endless belt have been proposed.

  Factors causing fluctuations in the moving speed of the endless belt include the eccentricity of the driving roller, the eccentricity of parts such as gears used in the drive transmission system, the gear tooth pitch error, and the thickness deviation fluctuation over one end of the endless belt. I know it. These cause a speed fluctuation of the endless belt in the rotation cycle of each part.

  As a technique for measuring the moving speed of the endless belt, for example, proposed in [Patent Document 1] and [Patent Document 2], a detection signal is detected on the endless belt in order to detect the speed fluctuation of the endless belt. There is a technique for transferring a toner image and reading the pattern by a detecting means. This is based on the fact that when the speed of the endless belt varies, the pattern formation interval varies.

  Moreover, as a technique for measuring the moving speed of the endless belt, for example, [Patent Document 3], [Patent Document 4], a rotary encoder is installed on a driven roller around which an endless belt is wound, A technology that reads the rotational fluctuation of the driven roller from the angular velocity of the rotary encoder and detects the speed fluctuation of the endless belt, proposed in [Patent Document 5], a mark is printed in advance on the surface of the endless belt, and this mark is detected by the sensor There is a technique for detecting the speed fluctuation of the endless belt by detecting the above, and a technique for using a means for detecting the amount of movement by installing equally spaced slit patterns on the endless belt surface.

  Conventionally, the drive motor that drives the endless belt is controlled so as to cancel the speed fluctuation of the endless belt detected using this technique. For example, in [Patent Document 1], it is proposed to control the drive motor so as to cancel the detected vibration component detection information related to the periodic rotational fluctuation.

  As described above, the conventional technique detects an endless belt moving speed fluctuation and controls the rotational speed and the amount of rotation of the drive motor on the basis of the fluctuation to move the endless belt at a constant speed. In addition, in an image forming apparatus, it has been expected to obtain a high-quality image output free from positional deviation and density unevenness by applying such a control mechanism to the image forming apparatus.

Japanese Patent No. 3186610 JP-A-10-186787 JP-A-4-172376 Japanese Patent Laid-Open No. 4-234064 Japanese Patent Laid-Open No. 6-130871

However, the rotational speed control technology of the drive motor based on the detected speed fluctuation information of the endless belt has the following problems.
Many endless belt driving devices used in image forming apparatuses use inexpensive motors from the viewpoint of cost reduction, and in order to use such motors efficiently, the driving force from the motor is a gear. Is transmitted to the drive roller via a speed reduction mechanism.
Then, in addition to the periodic fluctuations described above, in such a speed reduction mechanism, a transmission error due to the rigidity of the components constituting the reduction mechanism and the torsional rigidity of the shaft occurs. This transmission error becomes a factor that the moving speed of the endless belt is not stable even when the rotational speed of the motor is controlled.

Further, the factor that the moving speed of the endless belt is not stable is also generated by the endless belt itself.
When the endless belt is installed in an image forming apparatus, the endless belt has good adhesion to the toner and recording medium to be carried, thereby preventing the lack of characters and uniformity even for paper with poor flatness. Therefore, the toner image is molded from an elastic material so as to elastically follow the toner layer and local unevenness of the paper having poor smoothness at the transfer portion. In this way, the endless belt made of an elastic body is excellent in that it prevents excessive transfer pressure from being applied to the toner layer. The same can be said when an endless belt is installed in another device.
However, in the case of such an elastic belt body, due to load and temperature fluctuations, belt expansion and contraction and belt thickness change occur, affecting the belt conveyance speed.

  The resin used for forming the elastic belt includes polycarbonate, fluororesin (ETFE, PVDF), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, and styrene-vinyl chloride copolymer. Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer) Polymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer ) One or two or more types of resin selected from the group consisting of and the like.

  Due to these factors, in the conventional technology for controlling the drive motor, for example, it is difficult to stabilize the moving speed of the endless belt at an important part in image formation such as a transfer portion to an intended speed. In order to perform feedback control by detecting the speed of the belt surface, it is necessary to design a control controller that takes into account the transmission characteristics including the rigidity of the transmission mechanism and endless belt, which complicates the control system. . Further, even if such feedback control is performed, the target accuracy may not be achieved due to an unstable control system due to insufficient rigidity of the transmission mechanism and the endless belt.

As described above, the problem of the prior art for controlling the drive motor is that the transmission error due to the rigidity of the transmission mechanism and the endless belt between the control mechanism to be handled and the handling result obtained as the conveyance speed of the endless belt at the desired position. This is caused by the presence of expansion and contraction and temperature change.
Therefore, if the handling control mechanism can control the transport speed of the endless belt at the desired position directly or in a manner that reduces the influence of intervening members, it is possible to control the speed of the endless belt more stably and accurately. It is clear that there is.

  The present invention eliminates fluctuations in travel, such as fluctuations in the conveyance speed of endless belts such as intermediate transfer belts, photoreceptor belts, and paper conveyance belts, without controlling the rotational drive source of the endless belt with high accuracy. It is an object of the present invention to provide a belt running stabilization device for stabilization and an image forming apparatus and other devices such as a copying machine, a facsimile, and a printer having the same.

In order to achieve the above object, a first aspect of the present invention provides a winding member around which an endless belt is wound, and a drive for displacing the winding member so as to cancel a variation in traveling speed in a predetermined section of the endless belt. Means, a tension applying member for applying a predetermined tension to the endless belt, a drive member for rotating the endless belt by winding the endless belt together with the winding member at a position different from the predetermined section, The amount of change in the travel path length from the drive member of the endless belt to the predetermined section is determined by the amount of displacement of the winding member, and the travel speed of the endless belt in the predetermined section is equivalent to the change in the travel path length. by utilizing the change, the displacement of the winding member by the drive means, control for controlling so as to cancel the variation of the running speed in the predetermined interval And a stage, the winding member, the drive member is wound around the endless belt between the said position and the predetermined section with wound an endless belt, the variation of the running speed of the endless belt Based on the travel speed fluctuation amount in the predetermined section predicted based on the travel speed fluctuation amount or the endless belt thickness fluctuation profile detected by the detection means for detecting the above, The amount of displacement of the wrapping member that cancels the fluctuation of the traveling speed in a predetermined section is determined, and the tension of the endless belt is predetermined by the tension applying member by displacing the wrapping member by the driving means based on the amount of displacement. Bell by changing the traveling path of the endless belt while keeping the tension canceling the variation of the running speed of the endless belt in the predetermined section It is in the running stabilizing device.

  According to a second aspect of the present invention, in the belt running stabilization device according to the first aspect, the driving means includes a guide member for sliding the winding member to displace the winding member. To do.

  According to a third aspect of the present invention, in the belt running stabilization device according to the second aspect, the guide member is disposed corresponding to a non-contact position of the winding member with the endless belt. And

  According to a fourth aspect of the present invention, in the belt running stabilization device according to the second or third aspect, the winding member is a rotating body that rotates following the endless belt.

  According to a fifth aspect of the present invention, in the belt running stabilization device according to the first aspect, the winding member is a guide member that slides on the endless belt.

According to a sixth aspect of the present invention, in the belt running stabilization device according to any one of the second to fifth aspects, the surface of the guide member that slides on another member has a curved surface with a predetermined curvature. It is characterized by that.

A seventh aspect of the present invention is the belt travel stabilization device according to any one of the second to sixth aspects, wherein the entire guide member is formed using a material having a low friction coefficient. And

The invention according to claim 8 is the belt travel stabilization device according to any one of claims 2 to 6, wherein a surface of the guide member that slides on the other member uses a material having a low friction coefficient. It is characterized by being formed.

According to a ninth aspect of the present invention, in the belt running stabilization device according to any one of the second to eighth aspects, the surface of the guide member that engages with another member has a gas lubrication processing section. It is characterized by.

According to a tenth aspect of the present invention, in the belt running stabilization device according to any one of the second to eighth aspects, a portion of the guide member that engages with another member has a bearing structure. And

According to an eleventh aspect of the present invention, in the belt travel stabilization device according to any one of the first to tenth aspects, the driving means includes a rotational driving means for generating a rotational motion, and a rotational motion by the rotational driving means. characterized by chromatic and a drive conversion mechanism for converting the linear motion.

According to a twelfth aspect of the present invention, in the belt travel stabilization device according to the eleventh aspect , the drive conversion mechanism is engaged with the eccentric cam that is rotationally driven by the rotational driving means, and the eccentric cam is engaged with the eccentric cam. And a driven member that is driven in a linear direction by rotation.

According to a thirteenth aspect of the present invention, in the belt travel stabilization device according to the eleventh aspect , the drive conversion mechanism is rotated by the rotation driving means, and the rotation member meshes with the rotation member to rotate the rotation member. And a driven member that is driven in a linear direction.

A fourteenth aspect of the present invention is the belt travel stabilization device according to any one of the first to thirteenth aspects, wherein the tension of the endless belt wound by the winding member displaced by the driving means is detected. It has a detection means, and the control means limits the amount of displacement of the winding member by the drive means according to the tension of the endless belt detected by the detection means.

According to a fifteenth aspect of the present invention, there is provided the belt travel stabilization device according to any one of the first to fourteenth aspects, an endless belt wound around the winding member, and the endless belt together with the winding member. An image forming apparatus having a wound driving member for driving the endless belt.

According to a sixteenth aspect of the present invention, in the image forming apparatus according to the fifteenth aspect , the endless belt is provided as a conveying member for conveying a recording medium in the predetermined section.

According to a seventeenth aspect of the present invention, in the image forming apparatus according to the fifteenth aspect , the endless belt is provided as an image carrier.

According to an eighteenth aspect of the present invention, in the image forming apparatus according to the seventeenth aspect , the image forming apparatus includes an image forming unit configured to carry an image on the endless belt in the predetermined section.

According to a nineteenth aspect of the present invention, in the image forming apparatus according to the fifteenth aspect , the endless belt is provided as an intermediate transfer member to which an image is transferred in the predetermined section.

The present invention relates to a winding member around which an endless belt is wound, drive means for displacing the winding member in order to counteract fluctuations in travel speed in a predetermined section of the endless belt, and applying a predetermined tension to the endless belt. a tensioning member, wound around the endless belt together with the winding member in a position different from the above predetermined section, and a drive member for rotating the endless belt, said endless belt by a displacement amount of the winding member The driving means utilizes the fact that the amount of change in the travel path length from the drive member to the predetermined section is determined, and the travel speed of the endless belt in the predetermined section changes by the amount of the change in the travel path length. the displacement of the winding members by, and control means for controlling so as to cancel the variation of the running speed in the predetermined interval, the winding member, the upper Drive member is wound around the endless belt between the said position and the predetermined section with wound an endless belt, for detecting the variation of the running speed of the endless belt detection means the predetermined detected by The winding for canceling the fluctuation of the traveling speed in the predetermined section based on the fluctuation amount of the traveling speed in the predetermined section predicted based on the fluctuation amount of the traveling speed in the section or the thickness fluctuation profile of the endless belt. A displacement amount of the member is determined, and the winding member is displaced by the driving means based on the displacement amount, whereby the traveling path of the endless belt is changed while the tension applying member keeps the tension of the endless belt at a predetermined tension. at some belt traveling stabilizer for canceling the variation of the running speed of the endless belt in the predetermined section by the endless belt The variation of the running, it is possible to provide a belt traveling stabilizer capable without stabilizing resolved with high precision by performing control for the rotary drive source of the endless belt.

  If the driving means has a guide member for sliding the winding member to displace the winding member, the driving member displaces the winding member by abutting the guide member and positions the winding member. It is possible to provide a belt traveling stabilization device that can regulate and stabilize fluctuations in travel of the endless belt with high accuracy without performing control on the rotational drive source of the endless belt.

  Assuming that the guide member is disposed corresponding to the non-contact position of the winding member with the endless belt, while avoiding the influence on the traveling of the endless belt by disposing the guide member, It is possible to provide a belt running stabilization device that can eliminate and stabilize fluctuations in running of an endless belt with high accuracy without controlling the rotational drive source of the endless belt.

  Assuming that the winding member is a rotating body that rotates following the endless belt, the movement of the endless belt can be changed by using the same configuration as the conventional one in which the endless belt is wound. Therefore, it is possible to provide a belt running stabilization device that can be eliminated and stabilized with high accuracy without performing control for the above.

  If the winding member is a guide member that rubs against the endless belt, the fluctuation of the travel of the endless belt is controlled with respect to the rotational drive source of the endless belt while reducing the number of parts and reducing the cost. Therefore, it is possible to provide a belt running stabilization device that can be eliminated and stabilized with higher accuracy.

  If the surface of the guide member that rubs against the other member has a curved surface with a predetermined curvature, the load on the other member rubbed by the guide member is reduced, and fluctuations in the travel of the endless belt can be reduced. Thus, it is possible to provide a belt travel stabilization device that can be eliminated and stabilized with higher accuracy without controlling the rotational drive source.

  If the entire guide member is formed using a material having a low coefficient of friction, the guide member that can be manufactured easily can be used while reducing the load on other members that the guide member rubs. It is possible to provide a belt travel stabilization device that is relatively easy to manufacture and can eliminate and stabilize fluctuations in travel of an endless belt with high accuracy without controlling the rotational drive source of the endless belt. it can.

  If the surface of the guide member that rubs against other members is formed using a material having a low coefficient of friction, the guide member can be rubbed while using the guide member that is easy to ensure rigidity. It is possible to provide a belt running stabilization device that can reduce and stabilize the movement of the endless belt with higher accuracy without reducing the load on the member and without controlling the rotational drive source of the endless belt. .

  If the surface of the guide member that engages with the other member has a gas lubrication processing portion, the gas lubrication processing portion causes the load of the other member that the guide member rubs against, causing an adverse effect on the endless belt. Thus, it is possible to provide a belt running stabilization device that can reduce and stabilize fluctuations of the endless belt without being given, and can eliminate and stabilize the fluctuation of the endless belt with higher accuracy without controlling the rotational drive source of the endless belt.

  If the portion of the guide member that engages with the other member has a bearing structure, the guide member can be rubbed by a highly versatile bearing structure that is generally used to reduce friction. A belt that reduces the load of members without adversely affecting the endless belt, and can eliminate and stabilize fluctuations in the travel of the endless belt with higher accuracy without controlling the rotational drive source of the endless belt. A travel stabilization device can be provided.

  If the driving means has a rotational driving means for generating a rotational motion and a drive conversion mechanism for converting the rotational motion by the rotational driving means into a linear motion, it is generally used as a power source and is highly versatile. It is possible to use a rotational drive means, and using this as a drive source, fluctuations in travel of the endless belt can be eliminated and stabilized with high accuracy without performing control over the rotational drive source of the endless belt. A belt running stabilization device can be provided.

  Assuming that the drive conversion mechanism has an eccentric cam that is rotationally driven by the rotational driving means and a driven member that is engaged with the eccentric cam and is driven in a linear direction by the rotation of the eccentric cam, It is possible to use a general-purpose and highly versatile rotational drive means, and using this as a drive source, it is possible to accurately control fluctuations in the travel of the endless belt without controlling the rotational drive source of the endless belt. In particular, the amount of eccentricity of the eccentric cam corresponds to the amount that cancels the fluctuation amount of the component that fluctuates the travel of the endless belt, and the rotation is driven by synchronizing the rotation drive means. Since the fluctuation of the component can be eliminated by one rotation of the driving means, the control is facilitated and the motor is driven by driving at a constant speed with less burden and without reverse rotation. It is possible to provide a belt traveling stabilizer which can be eliminated minute fluctuations.

  If the drive conversion mechanism has a rotating member that is rotationally driven by the rotational driving means and a driven member that meshes with the rotating member and is driven in a linear direction by the rotation of the rotating member, the drive conversion mechanism is generally used as a power source. It is possible to use a highly versatile rotational drive means used in the above, and with this as a drive source, fluctuations in the travel of the endless belt can be eliminated with high accuracy without controlling the rotational drive source of the endless belt. It is possible to control the movement of the endless belt with a high degree of freedom by canceling the fluctuations of various components that vary the running of the endless belt according to the control accuracy of the rotation drive means, and to make the running of the endless belt more stable. It is possible to provide a belt running stabilization device that can be made to be effective.

  The detecting means detects the tension of the endless belt wound by the winding member displaced by the driving means, and the control means performs the same winding by the driving means according to the tension of the endless belt detected by the detecting means. If the amount of displacement of the member is limited, the fluctuation in the travel of the endless belt can be further increased without controlling the rotational drive source of the endless belt and without causing an excessive change in the tension of the endless belt. A belt running stabilization device that can be eliminated and stabilized with accuracy can be provided.

  The present invention provides the belt travel stabilization device according to any one of claims 1 to 13, an endless belt wound around the winding member, and the endless belt wound around the winding member. Since the image forming apparatus includes the driving member for driving the endless belt, the belt traveling stabilizing device that exhibits the above-described effects and the endless belt that stabilizes the traveling by the belt traveling stabilizing device are provided. Thus, it is possible to provide an image forming apparatus capable of eliminating and stabilizing the fluctuation with high accuracy without performing control on the rotational drive source of the endless belt, and performing high-quality image formation.

  If the endless belt is provided as a conveying member that conveys the recording medium in a predetermined section, the belt traveling stabilizing device that exhibits the above-described effects and the endless belt that stabilizes traveling by the belt traveling stabilizing device are provided. The fluctuations in travel can be eliminated and stabilized with high precision without controlling the rotational drive source of the endless belt, and the recording medium can be transported with high precision and stability. It is possible to provide an image forming apparatus capable of performing the image formation.

  If it has an endless belt as an image carrier, it has a belt traveling stabilization device that exhibits the above-described effects, and an endless belt that stabilizes traveling by this, so that the endless belt travel fluctuations can be reduced. Therefore, it is possible to eliminate and stabilize the image carrier with high accuracy without performing control on the rotation drive source of the image, and it is possible to stably run the image carrier with high accuracy. It is possible to provide an image forming apparatus that can stably perform the formation accuracy and the position accuracy with high accuracy and can perform high-quality image formation.

  If it has an image forming means for carrying an image on an endless belt in a predetermined section, it has a belt running stabilization device that exhibits the above-mentioned effects and an endless belt that stabilizes running by this, The fluctuations in the travel of the endless belt can be eliminated and stabilized with high accuracy without controlling the rotational drive source of the endless belt, and the travel of the image carrier can be stably performed with high accuracy. For example, when the exposure unit is provided as the image forming unit, the exposure can be performed with high accuracy and the exposure position is prevented from being shifted. For example, when the development unit is provided as the image forming unit, the development is performed. Therefore, it is possible to provide an image forming apparatus capable of forming a high-quality image.

  If it has an endless belt as an intermediate transfer body to which an image is transferred in a predetermined section, it has a belt running stabilization device that exhibits the above-described effects, and an endless belt that stabilizes running thereby, and is endless. Because fluctuations in belt running can be eliminated and stabilized with high accuracy without controlling the rotational drive source of the endless belt, and running of the intermediate transfer member can be carried out with high accuracy and stability. It is possible to provide an image forming apparatus capable of stably transferring an image to an intermediate transfer member with high accuracy and capable of forming a high-quality image.

  FIG. 1 schematically shows an image forming apparatus to which the present invention is applied and capable of forming a black and white image or a color image. The image forming apparatus 1 is a copying machine, but may be another image forming apparatus such as a printer such as a facsimile or a color laser printer, or a multifunction machine of a copying machine and a printer. The image forming apparatus 1 performs image forming processing based on the read image information or image signals corresponding to image information input from the outside. The same applies to the case where the image forming apparatus 1 has a facsimile function and is used as a facsimile. The image forming apparatus 1 can form an image using plain paper generally used for copying, OHP sheets, thick paper such as cards and postcards, and envelopes as sheet-like recording media. .

  The image forming apparatus 1 has a tandem structure in which photosensitive drums 20Y, 20M, 20C, and 20BK, which are photosensitive bodies as a plurality of image carriers that can form images corresponding to yellow, magenta, cyan, and black, are arranged in parallel. The visible image formed on each photoconductor drum 20Y, 20M, 20C, 20BK is used as an endless belt that can run in the direction of arrow A1 while facing each photoconductor 20Y, 20M, 20C, 20BK. The image is superimposed and transferred onto a transfer sheet as a recording medium conveyed on a transfer belt 11 which is a sheet conveying belt as a conveying member. The photosensitive drums 20Y, 20M, 20C, and 20BK are arranged in this order from the upstream side in the A1 direction.

  The image forming apparatus 1 includes an image forming unit 10Y serving as a yellow forming unit and an image forming unit serving as a red forming unit as image stations serving as image forming units capable of forming images corresponding to colors of yellow, magenta, cyan, and black. It includes a unit 10M, an image forming unit 10C that is a blue forming unit, and an image forming unit 10BK that is a black forming unit.

  The image forming apparatus 1 includes a transfer belt 11 including the four image forming units 10Y, 10M, 10C, and 10BK, and the photosensitive drums 20Y, 20M, 20C, and 20BK facing each other. A unit 14 and an optical scanning device 8 serving as an optical writing device disposed above the four image forming units 10Y, 10M, 10C, and 10BK are provided.

  The image forming apparatus 1 also includes a sheet feeding device 61 serving as a sheet feeding cassette on which transfer sheets conveyed toward the photosensitive drums 20Y, 20M, 20C, and 20BK and the transfer belt 11 are stacked, and an image forming apparatus. 1, an image forming unit 10Y, 10M, and a transfer sheet conveyed from a sheet feeding device 61 or a manual feed tray 62 or a post-processing device 63 described later. A pair of registration rollers 4 that are fed out toward a transfer portion between each of the photosensitive drums 20Y, 20M, 20C, and 20BK and the transfer belt 11 at a predetermined timing in accordance with a toner image formation timing by 10C and 10BK, and transfer paper And a sensor (not shown) for detecting that the tip of the roller has reached the registration roller pair 4.

The image forming apparatus 1 is also provided with a fixing device 6 as a fixing unit for fixing the toner image onto the transfer paper onto which the toner image has been transferred, and the fixing transfer paper provided outside the image forming apparatus main body 1. either discharged by directly or staples or sorted or reversed, a paper discharge unit serving post-processing apparatus 63 for feeding to the registration roller pair 4 again is reversed, after being arranged on the side of the post-processing apparatus 63 And a paper discharge tray 17 on which the transfer paper discharged from the processing device 63 is stacked.

  The image forming apparatus 1 is also positioned at the top of the image forming apparatus 1 main body. The image forming apparatus 1 is a reading device 64 that reads a document, an automatic document feeder 65 that loads and stacks the documents toward the reading device 64, and image formation. An exhaust device 66 disposed at a position facing the optical scanning device 8 in the main body of the apparatus 1 and exhausting the air in the main body of the image forming apparatus 1 to the outside, and for stabilizing the running of the transfer belt 11 shown in FIG. A belt travel stabilization device 21 as a belt travel stabilization device, a control device (not shown) having a CPU (not shown) for controlling the overall operation of the image forming apparatus 1, and a drive source for rotationally driving the transfer belt 11. And a stepping motor (not shown).

  Although not shown, the photosensitive drums 20Y, 20M, 20C, and 20BK have an undercoat layer having a thickness of 3 μm containing a thermosetting melamine, an alkyd resin, and a light dispersing agent on a cylindrical aluminum substrate. This is a function-separated organic photoreceptor having an outer diameter of 30 mm, comprising a 0.5 μm thick charge generation layer containing titanyl phthalocyanine in butyral resin and a 25 μm thick charge transport layer using polycarbonate resin as a binder.

  The sheet feeding device 61 is disposed at the lower part of the main body of the image forming apparatus 1, and includes a feeding roller 3 as a paper feeding roller that contacts the upper surface of the uppermost transfer paper. Is rotated in the clockwise direction so that the uppermost transfer paper is fed toward the registration roller pair 4. The exhaust device 66 has an ozone filter 67 that removes ozone contained in the exhaust. The optical scanning device 8 irradiates the photosensitive drums 20Y, 20M, 20C, and 20BK with a laser beam L as a laser beam.

  With reference to FIG. 2, the configuration of the image forming units 10Y, 10M, 10C, and 10BK will be described as a representative of the configuration of the image forming unit 10BK including the photosensitive drum 20BK. Since the configurations of the other image forming units 10Y, 10M, and 10C are substantially the same, in the following description, for the sake of convenience, reference numerals assigned to the configurations of the image forming unit 10BK including the photosensitive drum 20BK are used. Corresponding reference numerals are given to the configurations of the other image forming units 10Y, 10M, and 10C, and detailed descriptions thereof are omitted as appropriate, and those with Y, M, C, and BK added to the end of the reference numerals, respectively. , Yellow, cyan, magenta, and black for image formation.

  The image forming unit 10BK includes, around the photosensitive drum 20BK, a transfer unit 12BK serving as a transfer roller that is a roller facing the photosensitive drum 20BK along a rotation direction B1, which is a clockwise direction in the drawing, and an image carrier cleaning unit. A cleaning device 40BK as a photosensitive member cleaning device, a neutralizing device 13BK as a neutralizing unit as a neutralizing unit, a charging device 30BK as a charging unit as a charging unit, and a developing unit as a developing unit as a developing unit as a developing unit. 50BK.

  As shown in FIG. 2, the optical scanning device 8 shown in FIG. 1 irradiates a region between the charging region and the development region of the photosensitive drum 20BK with the light-modulated laser light L, and the charging device BK The surface of the charged photosensitive drum 20BK is exposed to form an electrostatic latent image that is visualized as a black toner image by the developing device 50BK.

  In addition to the transfer belt 11, the transfer belt unit 14 wraps around the transfer belt 11, and a driving roller 15 as a driving member for rotationally driving the transfer belt 11, and a winding member around which the transfer belt is wound together with the driving roller 15. Driven rollers 18 and 19 as rotating bodies, a tension roller 16 as a tension applying member for applying a predetermined tension to the transfer belt 11 so that the transfer belt 11 runs stably, and a spring as a biasing member (not shown). have. The drive roller 15 is rotationally driven by the above-described stepping motor via a gear mechanism (not shown).

  In such a configuration, the surface of the photosensitive drum 20BK is charged to a potential of −800 to −850 V by the charging device 30BK along with the rotation in the B1 direction, and exposure scanning of the laser light L from the optical scanning device 8 is performed. An electrostatic latent image corresponding to the black color is formed, and the electrostatic latent image is developed with black toner by the developing device 50BK. The black toner image obtained by the development is transferred onto the transfer paper transported on the transfer belt 11 moving in the A1 direction by the transfer means 12BK, and foreign matters such as toner remaining after the transfer are removed by the cleaning device 40BK. It is used for the next charge removal and charging by the charging device 30BK.

  Similarly, the toner images of the respective colors are formed on the other photosensitive drums 20Y, 20M, and 20C. The formed toner images of the respective colors are transferred in the A1 direction by the transfer units 12Y, 12M, and 12C. 11 is sequentially transferred to the same position on the transfer paper conveyed, and a black toner image is transferred thereon as described above to form a composite color image.

  As described above, the superimposed transfer on the transfer paper is such that the visible image formed on each of the photoconductive drums 20Y, 20M, 20C, and 20BK is overlapped at the same position on the transfer paper in the process in which the transfer belt 11 moves in the A1 direction. From the upstream side in the A1 direction by applying voltage by the transfer means 12Y, 12M, 12C, and 12BK arranged to face the photosensitive drums 20Y, 20M, 20C, and 20BK with the transfer belt 11 interposed therebetween. The timing is shifted toward the downstream side.

  The transfer paper transported on the transfer belt 11 is fed from the sheet feeding device 61 by the feeding roller 3 and fed, or fed from the manual feed tray 62 or the post-processing device 63, and the registration roller pair 4 provides a sensor. Is sent in accordance with the timing at which toner images are formed on the photosensitive drums 20Y, 20M, 20C, and 20BK.

  When the transfer paper 11 is sequentially transferred and supported by toner images of all colors, the transfer paper 11 enters the fixing device 6 as the transfer belt 11 rotates in the A1 direction, and fixes the supported toner image by the action of heat and pressure. Then, a color image is fixedly formed on the transfer paper. The fixed transfer paper that has passed through the fixing device 6 is subjected to processing such as stacking on the paper discharge tray 17 through the post-processing device 63.

  In such an image forming process, it is important to stabilize the running of the transfer belt 11. That is, the transfer belt 11 is wound around the driven rollers 18 and 19 and a toner image on the photosensitive drums 20M, 20C, 20Y, and 20BK is transferred (hereinafter, this section is defined as an operation section that is a predetermined section). In FIG. 9, the transfer paper is transported and the toner images of the respective colors are sequentially transferred in the transfer section 25, so that the transfer belt in the transfer section 25 is transferred. 11, specifically, when the running speed and running position of the transfer belt 11 are unstable, the toner images of the respective colors are transferred in a shifted state, and an image in which an image defect such as a color shift occurs is formed. Therefore, it is extremely important to stabilize the traveling of the transfer belt 11 in the transfer section 25 in order to form a high-quality image.

  The travel speed and travel position of the transfer belt 11 are described as the travel of the transfer belt, and the travel speed and travel position of the transfer belt 11 are described as the travel fluctuation of the transfer belt. The amount of change in the travel position of the transfer belt 11 actually occupies a certain point on the transfer belt 11 compared to the position that the transfer belt 11 occupies in an ideal state where the travel speed does not vary. It indicates how much the position is displaced, that is, the distance. The change in the running position of the transfer belt 11 and the change in the running speed of the transfer belt 11 are equivalent. This point will become clear from the following description.

  Here, the unstable factors of the running of the transfer belt 11 will be described. The drive roller 15 has a predetermined eccentricity according to its processing accuracy, and this is one of the instability factors. Moreover, it becomes one of the unstable factors which the transmission error by the eccentricity of the gear which comprises a gear mechanism, and a tooth pitch error takes.

Variation in thickness deviation over one turn of the transfer belt 11 is also one of such instability factors. Such variation in thickness deviation causes fluctuations in the running speed of the transfer belt 11 in the transfer section 25, causing a state in which the toner image is transferred to a position shifted from a desired position on the transfer paper, or in the transfer section 25. Difference in speed between the photosensitive drums 20Y, 20M, 20C, and 20BK and the transfer belt 11 causes pixel collapse for each color toner image, resulting in image density called banding, as described above. This is because there is a deviation in the superposition of the toner images of the respective colors, and the deterioration of the image quality becomes remarkable. Such a banding problem is not only used when an endless belt is used as a conveying member like the transfer belt 11 but also used for primary transfer, secondary transfer, and the like as an intermediate transfer belt as an intermediate transfer member. The same occurs when used for exposure, development, and transfer as a photosensitive belt as an image carrier.

  In order to cancel the fluctuation of the travel in the transfer section 25 of the transfer belt 11 due to such an instability factor and cause the transfer belt 11 to travel in a stable state, the image forming apparatus 1 includes a driven roller 19 and a driven roller 19 as shown in FIG. A belt having driving means 22 for displacing the driven roller 19 and the above-mentioned control means for controlling the displacement of the driven roller 19 by the driving means 22 so as to cancel the fluctuation of the running in the transfer section 25 of the transfer belt 11. A travel stabilization device 21 is provided.

  The inventors have determined the travel path length of the endless belt from a certain roller around which the endless belt is wound, such as from the driving roller 15 to the transfer section 25 in the image forming apparatus 1, to a portion where travel is to be stabilized. It is found that the change correlates with the fluctuation of the travel of the endless belt in the portion where it is desired to stabilize the travel. From this knowledge, the member that regulates the belt conveyance path, that is, the member that displaces the winding member is used, and the endless belt By directly acting on the belt, we propose a technology that can stabilize the running of the endless belt more stably and accurately without controlling the drive source of the endless belt. The thing is the belt running stabilization device 21.

In the image forming apparatus 1, in order to appropriately drive the driving unit 22 by the control unit, it is necessary to know the traveling state of the transfer belt 11.
This running state of the transfer belt 11 can be known from the change in the running path length of the endless belt described above.
Therefore, first, the inventors have found the endless belt travel path length, in other words, the change in the transport path length, the endless belt travel fluctuation, specifically, the endless belt travel speed and the endless belt travel position. Will be described.

  As shown in FIG. 3, it is assumed that the position of the driven roller 19 is variable and rotates at either the position indicated by the solid line or the position indicated by the alternate long and short dash line in the figure. At this time, the travel path of the transfer belt 11 from the driving roller 15 to the transfer portion, which is included in the transfer section 25 and is adjacent to the driven roller 19, and is an area where the transfer roller 12BK and the photosensitive drum 20BK are opposed to each other, changes. Comparing the distance of this portion, that is, the traveling path length of the transfer belt 11 in such a traveling path, it can be seen that the traveling path length of the transfer belt 11 indicated by a one-dot chain line is longer.

Then, it can be seen that the travel path of the transfer belt 11 changes due to a change in the position of the driven roller 11, and the travel path length from the driving roller 15 to the transfer portion becomes longer or shorter.
Therefore, even if the drive roller 15 drives the transfer belt 11 at a constant speed, the position of the driven roller 18 changes, and the travel path length of the transfer belt 11 from the drive roller 15 to the transfer portion changes. The travel speed of the transfer belt 11 in the transfer portion changes as much as the length changes.

  In other words, when the drive roller 15 is driving the transfer belt 11 at a constant speed, the length of the transfer belt 11 that the drive roller 15 travels per unit time in the section from the drive roller 15 to the transfer portion, in other words, the feeding out. Although the amount is constant, when the driven roller 19 moves from the solid line position to the one-dot chain line position and the travel path of the transfer belt 11 becomes longer, the transfer by the drive roller 15 is increased by the length of the travel path within the travel time. The amount of passage of the transfer belt 11 in the transfer portion is larger than the amount of feeding of the belt 11, and the running speed of the transfer belt 11 in the transfer portion is increased. Conversely, when the driven roller 19 moves from the one-dot chain line position to the solid line position, the passing amount of the transfer belt 11 at the transfer portion is reduced by the amount that the travel path of the transfer belt 11 is shortened within the moving time. Thus, the traveling speed of the transfer belt 11 in the transfer portion is reduced.

Therefore, by changing the position of the driven roller 19, the traveling speed of the transfer belt 11 in the transfer portion, that is, the transfer section 25, can be changed according to the amount of movement of the driven roller 19.
By using this to control the travel path length of the transfer belt 11, it becomes possible to cancel the travel fluctuation of the transfer belt 11 due to the transmission error caused by the eccentricity of the drive roller 15 and the rotation cycle of the gear mechanism. It is possible to reduce the positional deviation of the transfer image on the paper, that is, the toner image of each color, and to transfer the image with high accuracy. This is realized by the belt running stabilization device 21.

  As described above, it has been found that the movement of the endless belt in a certain portion can be controlled by displacing the winding member around which the endless belt is wound. That is, in order to cancel the fluctuation of the endless belt traveling, the relationship between the position of the wrapping member to be displaced and the position of the endless belt where the traveling state varies thereby, and the amount of displacement of the wrapping member It is necessary to know the relationship between the endless belt travel fluctuation amount. The inventors clarified these in proposing the belt running stabilization device 21. This will be described below.

The relationship between the position of the wrapping member to be displaced and the position of the endless belt whose traveling state fluctuates thereby. This relationship can be described along the image forming apparatus 1 by varying the traveling of the transfer belt 11 in the transfer section 25. In order to cancel, it is in agreement with the relationship where the drive means 22 should be arrange | positioned.

  First, a generalized endless belt travel route shown in FIG. 4 will be described. The transport system of the endless belt 411 shown in FIG. 4 includes a driving roller 415, a tension roller 416, and four driven rollers 418, 419, 401, and 402. FIG. 4 also shows the rotation direction of the drive roller 415 and the conveyance direction of the endless belt 411.

The conveying path of the transfer belt 411 wound around the driving roller 415, the driven rollers 418, 419, 401, 402, and the tension roller 416, that is, the traveling path is divided for each roller, and the divided sections are denoted by symbols A to F. Indicated.
For each of the sections A to F, a description will be given of a place where the driving means should be installed in order to control the fluctuation of the travel of the endless belt 11 in the section.

  In the section A, the transport amount and travel speed of the endless belt 411 are governed by the transport amount and travel speed of the endless belt 411 sent out by the drive roller 415, and the travel fluctuation in this section cannot be controlled. In the section B, the transport amount and travel speed of the endless belt 411 sent by the driving roller 415 are affected by the change in travel path due to the position variation of the driven roller 401, and the transport amount and travel speed of the endless belt 411 vary. . Therefore, it is possible to control the fluctuation of the travel of the endless belt 411 in the B section by disposing the driving means corresponding to the disposition position of the driven roller 401.

  The C section is affected by the driven roller 401 and the driven roller 402 for the same reason as in the B section. However, since it is the tension roller 416 that forms the C section together with the driven roller 402, even if the tension of the endless belt 411 changes in the C section, this change is absorbed by the tension roller 416, resulting in the endless belt. No tension change of 411 occurs. For example, when the travel path length of the endless belt 411 increases, the tension of the endless belt 411 increases, so the tension roller 416 moves in a direction in which the travel path of the endless belt 411 decreases to keep the tension of the endless belt 411 constant.

  In D section, there is no influence by the position fluctuation of the driven roller 402 and the driven roller 403. This is because the positional variation of the driven roller 402 and the driven roller 403 is eliminated by the tension roller 416 regarding the D section. In addition, since the tension roller 416 itself has an effect of eliminating fluctuations in the travel of the endless belt 411, it is unnecessary to dispose a driving unit with respect to the tension roller 416.

In the section E, the transport amount and travel speed of the endless belt 411 that the drive roller 415 pulls in are affected by the change of the travel route due to the position variation of the driven roller 419, and the transport amount and travel speed of the endless belt 411 vary. Therefore, it is possible to control the fluctuation of the travel of the endless belt 411 in the E section by disposing the driving means corresponding to the disposition position of the driven roller 419. In the D section, the C section is affected by the driven roller 419 and the driven roller 418 for the same reason as described above. Further, this influence does not propagate to the C section for the same reason as described above.
In the F section, the transport amount and travel speed of the endless belt 411 are governed by the transport amount and travel speed of the endless belt 411 drawn by the drive roller 415, and the travel fluctuation in this section cannot be controlled.

  In consideration of the above, when the transfer section is in section B, the driving means is disposed corresponding to the position where the driven roller 401 is disposed to control the fluctuation of the travel of the endless belt 411 in the section B. Is possible. When the transfer section is in section C, it is possible to control fluctuations in the travel of the endless belt 411 in section C by disposing driving means corresponding to the positions where the driven roller 401 or the driven roller 402 is disposed. is there. However, it is desirable to dispose the driving means corresponding to the disposition position of the driven roller 402 closer to the section C to be controlled.

  When the transfer section is in section D, it is possible to control fluctuations in the travel of the endless belt 411 in section D by disposing driving means corresponding to the positions where the driven roller 419 or the driven roller 418 is disposed. is there. However, it is desirable to dispose the driving means corresponding to the disposition position of the driven roller 418 closer to the section D to be controlled. When the transfer section is in section E, it is possible to control the variation in travel of the endless belt 411 in section E by disposing the driving means corresponding to the position where the driven roller 419 is disposed.

  Therefore, if the section E corresponds to the transfer section 25 in the image forming apparatus 1, the winding position of the endless belt 11 at the position where the driven roller 19 is disposed, which corresponds to the position where the driven roller 419 is disposed, is controlled. It can be seen that the movement of the endless belt 11 in the transfer section 25 can be controlled by providing the driving means 22.

  In the above description performed with reference to FIG. 4, it is assumed that there is a transfer section in each of the sections A to F in order to correspond to the transfer section 25 in the image forming apparatus 1. The relationship between the position of the driving means and the section in which the fluctuation of the travel of the endless belt can be controlled by this is the same even when the exposure unit, the developing unit, and the conveyance unit are present in each of the sections instead of the section. An endless belt having sections corresponding to the exposure unit and the development unit is an image carrier having such a section as an image forming section as an action section. An endless belt having sections corresponding to transfer sections such as a primary transfer section and a secondary transfer section is an intermediate transfer member having such sections as transfer sections as working sections.

The relationship between the displacement amount of the winding member and the travel variation amount of the endless belt. This relationship is described along the image forming apparatus 1. In order to cancel the travel variation of the transfer belt 11 in the transfer section 25, the drive This is consistent with the relationship of the magnitude of the driving amount by means 22.

FIG. 5 shows two circles corresponding to the cross section of the member around which the endless belt is wound. Points O ₂ and O ₂ ′ indicate the centers of the curvatures of the positions where the positions of the rollers around which the endless belt is wound or the portions where the endless belt contacts the endless belt are variable. Point O ₁ is the center of another member adjacent to the member centered at point O ₂ , point O ₂ ′, that is, the center of this roller when this member is a roller, and this member simply wound an endless belt In the case of a member, the center of curvature of the portion of the member that contacts the endless belt is shown. A change in the travel path length of the endless belt when the center of the member whose position is variable is displaced between the point O ₂ and the point O ₂ ′ is obtained.

The axis connecting point O ₁ and point O ₂ ′ is the X axis, and the distance between these two points is L ₀ ′. The axis connecting point O ₂ ′ and point O ₂ is the Z axis, and the distance between these two points is e ₂ . The crossing angle between the X axis and the Z axis is θ ₂ . R _1, R ₂ each point _{O 1,} 'the members about the point _{O 1,} point _{O 2} (point _{O 2} point _{O 2} (point _{O 2)'} distance or the point _{O 1} from) to the endless belt , The radius of a circle centered on the point O ₂ (point O ₂ ′).

The travel path length of the endless belt includes a length L of a line segment that contacts the two circles, and a length Lg of a portion where the endless belt is wound around a member centered on the point O ₂ (point O ₂ ′). It shall be expressed as the sum of Here, the part of the sum of the length L and the length Lg is used as the travel path length of the endless belt. This part is caused by a path change due to the movement of the point O ₂ ′ and the point O ₂ ′ at the center. This is because there is no need to consider other winding portions. The length L and the length Lg are expressed by the following formulas (5) and (6) using the following formulas (1) to (4).

Therefore, in order to obtain a specific value of the change in the travel path length of the endless belt when the center of the member whose position is variable is displaced between the point O ₂ and the point O ₂ ′, the variable e ₂ is used. Substituting the values before and after the movement, the values of the equations (1) to (6) are obtained, and the difference between the route calculation results obtained as L + Lg is obtained.

  6 shows the travel path of the endless belt between the member whose position is movable and the member adjacent to the endless belt wound around the endless belt shown in FIG. 5 of the actual endless belt provided in the image forming apparatus 1. It is shown in a developed manner on a travel route of an endless belt corresponding to the travel route. That is, a traveling path of the endless belt determined by a member around which the endless belt is wound and whose position is movable and two members adjacent to the upstream and downstream sides of the member in the traveling direction of the endless belt are illustrated.

_A point O _A and a point O _A ′ indicate the centers of the curvatures of the positions where the positions of the rollers around which the endless belt is wound or the portions where the endless belt is wound are in contact with the endless belt. Point O _B and Point O _C are the centers of the other two members adjacent to the member centered at point O _A and point O _A ′, that is, the center of this roller if these members are rollers, In the case where the member is simply a member around which an endless belt is wound, the center of curvature of the portion of the member that contacts the endless belt is shown.

Point O _A, the length of a line contact point O _B into two circles centered respectively with L _AB. The length of the line segment in contact with the two circles centered at the points O _A and O _C is defined as L _AC . The axis connecting point O _B and point O _A ′ is the X _AB axis, and the distance between these two points is L _0AB ′. Point _{O C,} the axis connecting the point _{O A} 'and _{X AC} axis. The axis connecting point O _A ′ and point O _A is the Z axis, and the distance between these two points is e _A.
The crossing angle between X _AB and Z axes are the theta _A. The crossing angle between X _AC and Z axes are the theta _B. The crossing angle between the X _AB axis and the X _AC axis is α. This angle α is hereinafter referred to as an axis crossing angle.
At this time, θ _B is defined by the following equation (7).

By substituting these parameters into the equations (1) to (6) and determining the change ΔL _BC of the travel path length of the endless belt at the movement amount e _A , the following equation (8) is obtained.

However, L _AB ′ and L _AC ′ are travel path lengths of the endless belt before the movement (when the movement amount is 0).

  That is, the equation (8) becomes the following equation (9).

However,

It is.
Here, using the formulas (9) to (13), L _0AB = 100 [mm], L _0AC = 100 [mm], R _A = 15 [mm], R _B = 15 [mm], R _C = 15 [mm], α = 1.5 [rad], θ _A = 1 [rad] are set as parameters, and the movement amount of the member whose position is variable and the two members adjacent to this member are wound The relationship with the amount of change in the travel path length of the endless belt is shown in FIG.

ΔLAB in the figure indicates the variation in the travel path length of the endless belt in the L _AB, ΔLAC in the figure shows the variation of the travel path length of the endless belt in L _AC. The sum of these amounts of change is the amount of change ΔLBC of the entire travel path length. Control is performed using a numerical value indicating the inclination of the ΔLBC graph, that is, the travel path length change amount of the endless belt per unit travel.

  Now, in order to control the endless belt to travel in a desired state, that is, to cancel the fluctuation of the endless belt, the position of the wrapping member to be displaced and the endless belt whose traveling state varies depending on the position. The relationship with the position and the relationship between the amount of displacement of the winding member and the variation in travel of the endless belt have been clarified. However, in order to perform control to actually cancel the variation in travel of the endless belt, the endless belt It is necessary to know the fluctuation amount of the running.

In order to detect such a fluctuation amount, a case will be described in which detection means for detecting the fluctuation amount of the travel of the endless belt is provided.
For such detection means, a conventional method is adopted. For example, as described in [Patent Document 1] and [Patent Document 2], a resist pattern is formed as a detection object as a detection toner image on a photosensitive member as an image carrier. There is a method of transferring onto an intermediate transfer belt as an endless belt as an intermediate transfer body and reading this pattern with a reading unit as a detecting means. This is based on the fact that if the speed of the intermediate transfer belt changes during transfer, the pattern formation interval changes, and the resist pattern passage timing is arranged downstream of the photoconductor in the intermediate transfer belt running direction. By reading with the above-described reading unit, fluctuations in the running of the intermediate transfer belt are detected. The transfer belt 11 in this embodiment corresponds to an intermediate transfer belt which is an endless belt.

  Further, for example, as described in [Patent Document 5] already described, by printing a mark as a detection object in advance on the surface of the endless belt, and detecting this mark with a sensor as a detection means, There is a method for detecting the speed fluctuation of the endless belt. In addition, for example, as described above, there is a method in which a slit pattern having equal intervals as a detection object is provided on the surface of the endless belt and detecting means for detecting the movement amount is used.

  Further, for example, as described in [Patent Document 3] and [Patent Document 4], a rotary encoder is installed on the shaft of a driven roller around which an endless belt is wound, and the driven roller is detected from the angular velocity of the rotary encoder. There is a method using a detecting means for reading the rotational fluctuation of the belt and detecting the speed fluctuation of the endless belt. Unlike the above-described methods, this method does not use the detection object attached to the endless belt and the detection means for detecting the detection object, and the endless belt travels by the rotational fluctuation of the driven roller around which the endless belt is wound. It detects the amount of fluctuation. That is, an encoding roller, which is a driven roller having a rotary encoder on the shaft, rotates with the travel of the endless belt, whereby the rotary encoder rotates to detect the rotational speed and detect the travel speed of the endless belt It is.

  However, in this method, a detection error occurs. For example, when the follower roller 19 shown in FIG. 3 is used as an encoding roller, and the movement of the transfer belt 11 is detected by the rotation of the encoding roller 19, the transfer belt 11 that is an endless belt like the encoding roller 19 is used. In the configuration in which the shaft of the encoding roller 19 is wound, the rotation of the shaft of the encoding roller 19 causes the eccentricity of the encoding roller 19 itself or the encoding roller in addition to the fluctuation in the travel of the transfer belt 11 due to the eccentricity of the driving roller 15 as described above. 19 is affected by the thickness deviation variation of the transfer belt 11 wound around the belt 19, and therefore, only the variation in the travel of the transfer belt 11 due to the eccentricity of the drive roller 15 as described above cannot be accurately detected. is there.

  As another configuration example of detection means in which a detection error due to the eccentricity of the encoding roller itself occurs, a linear portion formed by stretching the endless belt is pressed against the endless belt and slips between the endless belt. There is a detecting means that includes an encoding roller disposed so as to be not in contact with a pinch roller facing the encoding roller, sandwiches the endless belt between the encoding roller and the pinch roller, and rotates the encoding roller following the endless belt. This detection means is less affected by the variation in thickness deviation of the endless belt, but is affected by the eccentricity of the encoding roller itself.

Such detection error components included in the data detected using the detecting means having the encoding roller driven and rotated by the endless belt are removed by performing correction processing on the detected data. It is possible.
For example, a filter process can be set to remove fluctuations in the rotation period of the encoding roller. It is also possible to set one home position on the encoding roller in advance, detect the rotation cycle fluctuation of the encoding roller, and subtract the fluctuation fluctuation of the encoding roller from the detection data based on the home position signal. It is.

  On the other hand, the endless belt thickness deviation fluctuation is caused by the endless belt running fluctuation caused by the endless belt thickness deviation fluctuation at the position where the endless belt is wound around the driving roller. This is a result of superimposing fluctuations in the travel of the endless belt caused by fluctuations in the belt thickness deviation.

  This superimposed variation is due to the influence of the same endless belt thickness variation deviation, and the positional relationship between the driving roller and encoding roller on the diameter and endless belt travel path is fixed. It is possible to analyze in advance how the influence of deviation fluctuations at the position wound around the roller and the position wound around the encoding roller are superimposed.

  In other words, by detecting in advance the rotation fluctuation of the encoding roller for one endless belt and analyzing the rotation period component of the endless belt, false detection due to belt thickness deviation fluctuation at the position wound around the encoding roller By analyzing the components, it is possible to obtain data relating to what kind of running fluctuation caused by the endless belt itself. Thus, it is possible to remove the obtained data by performing a correction process similar to the correction process for removing the fluctuation of the rotation cycle of the encoding roller.

  So far, in order to perform control for actually canceling fluctuations in the travel of the endless belt, a case has been described in which a detecting means for detecting the fluctuation amount of the travel of the endless belt is provided in order to know the fluctuation amount of the travel of the endless belt. However, as another method of knowing the fluctuation amount of the endless belt running, there is a method of measuring the accuracy of parts in the manufacturing process and predicting the fluctuation amount based on this.

  For example, the thickness of the endless belt is measured at a plurality of locations on the manufacturing process over one turn of the endless belt to obtain a profile of the thickness variation of the endless belt. The relationship between the thickness of the endless belt and the traveling speed of the endless belt and the variation in the travel of the endless belt using this relationship can be obtained as follows. As shown in FIG. 8, the running speed Vb of the endless belt 24 when the endless belt 24 is wound around the drive roller 23 is the belt effective in which the thickness of the endless belt 24 is generally said to be half of the belt thickness. When the thickness Bt ′ is used, and the radius Rd of the driving roller 23 and the angular velocity ωd of the rotation of the driving roller 23 are used, the following equation (14) is obtained.

  Here, from the average value of the thickness of the endless belt 24, the average value Bt0 ′ of the effective thickness of the endless belt 24 can be obtained. The belt conveyance average speed Vb0 obtained from the average value Bt0 ′ is obtained by the following equation (15) in the same manner as the equation (14).

The difference between the values obtained from the equations (14) and (15) becomes the speed fluctuation of the endless belt 24.
In order to perform the above-described control for actually canceling the fluctuation of the endless belt, the method of knowing the fluctuation amount of the endless belt and the method of removing the error included in the obtained fluctuation amount are cost, accuracy, From the reliability, select the most suitable belt according to the target belt transport system, that is, the endless belt, the drive roller wrapped around the endless belt, the driven roller, the drive source for driving the drive roller, and the transmission mechanism. do it. The method for knowing the fluctuation amount of the endless belt running and the method for removing the error included in the obtained fluctuation amount are not limited to those described above, and other known methods can be appropriately selected as described above.

By the method described above, it has become clear that the control means can control the drive means 22 to displace the driven roller 19 so as to cancel the fluctuations in travel in the transfer section 25 of the transfer belt 11.
Here, as a control method in which the control means controls the drive means 22, there are two types of feed forward control and feedback control as is generally the case.

  An example of feedforward control will be described. In the transfer section 25 shown in FIG. 9, the result of detecting the fluctuation of the transfer belt 11 using the above-described detection means, for example, the detection means having an encoding roller, is shown in FIG. FIG. 10 shows the above-described detection error corrected by filter processing. In FIG. 10, the vertical axis represents the fluctuation amount of the travel position of the transfer belt 11. The amount of change in the travel position is the position that the transfer belt 11 actually occupies compared with the position that the transfer belt 11 occupies in an ideal state where the transfer belt 11 does not vary in travel speed. This indicates whether or not the amount is shifted by a certain amount, that is, a distance, and is equivalent to a change in the traveling speed of the transfer belt 11.

  FIG. 10 shows a fluctuation in which a fluctuation with a period of about 6.5 seconds indicated by reference numeral 26a and a fluctuation with a period of about 0.7 seconds indicated by reference numeral 26b are superimposed. Since the cycle indicated by the reference numeral 26a is equal to the time for which the transfer belt 11 makes one rotation, it can be seen that it is a change in the travel position due to a thickness deviation change over one turn of the endless belt 11. Further, since the cycle indicated by reference numeral 26b is equal to the time for which the drive roller 15 rotates once, the eccentricity of the drive roller 15, the eccentricity of the gear disposed on the shaft (not shown) of the drive roller 15, and this gear are included. It can be seen that the variation due to the cumulative pitch error of the gear mechanism teeth is a synthesized variation of the running position.

  In order to cancel these two types of periodic fluctuations by feedforward control and drive the transfer belt 11 at a stable traveling speed without fluctuations in the traveling position, as shown in FIG. The components, here, the members 27 and 28 for defining the home positions are installed on the transfer belt 11 and the driving roller 15, respectively, and the members 27 and 28 are respectively opposed to the transfer belt 11 and the driving roller 15 as means for detecting the members 27 and 28. Sensors 81 and 82 are installed at the positions, respectively. The members 27 and 28 and the sensors 81 and 82 may be installed at arbitrary places.

  In FIG. 11, the output of the sensor 81 and the fluctuation of the running position of the transfer belt 11 in the transfer section 25 are measured simultaneously, and the rotation period of the transfer belt 11 is based on the time when the member 27 is detected by the sensor 81, that is, time 0. The result of having extracted a component as a fluctuation amount of a running position is shown. In FIG. 12, the output of the sensor 82 and the fluctuation of the running position of the transfer belt 11 in the transfer section 25 are measured simultaneously, and the rotation period of the driving roller 15 is based on the time when the member 28 is detected by the sensor 82, that is, time 0. The result of having extracted a component as a fluctuation amount of a running position is shown. In each case, filtering was performed as a method for extracting only the rotation period component.

  From the results shown in FIGS. 11 and 12, the control amount by the driving means 22, that is, the displacement amount is obtained. The driving direction by the driving means 22, that is, the displacement direction is the direction indicated by the broken arrow 29 in FIG. 9, and the displacement amount in the direction toward the tip of the arrow 29 is positive. The amount of displacement is determined from the slope value unique to the apparatus as shown in FIG. If the inclination value is 1.4, it can be said that the travel path length of the transfer belt 11 is increased by 1.4 mm if the displacement amount by the driving means 22 is +1 mm. The displacement amount is obtained by inverting the numerical values of the variation data shown in FIGS. 11 and 12 and dividing by 1.4.

  FIG. 13 shows a control amount, that is, a displacement amount by the driving means 22 for canceling the fluctuation shown in FIG. As shown in FIG. 11, since the variation of the traveling position is positive from 0 second, which is the time when the member 27 is detected, to about 1.8 seconds, the displacement by the driving means 22 at this time is The transfer belt 11 travels in the negative direction, which is the direction in which the travel path length becomes shorter.

FIG. 14 shows the amount of control, that is, the amount of displacement by the driving means 22 for canceling the fluctuation shown in FIG. FIG. 14 shows a result of extracting one rotation period component of the drive roller 15.
Therefore, every time the sensor 81 detects the member 27, the driving means 22 performs the control shown in FIG. 13, and every time the sensor 82 detects the member 28, the driving means 22 performs the control shown in FIG. The fluctuations in the rotation cycle of the belt 11 and the drive roller 15 are canceled out, the fluctuations in the running of the transfer belt 11 are eliminated, and the running is stabilized.

  FIG. 15 is a block diagram for determining the driving amount by the driving means 22 in order to eliminate and stabilize the fluctuation of the running of the transfer belt 11. Reference numerals 83, 84, and 85 in the figure respectively denote information on the displacement amount by the driving means 22 for canceling the fluctuation component of the rotation period of the transfer belt 11, the rotation period of the driving roller 15, and the rotation period of the stepping motor. The block which outputs based on a home position signal is shown.

  In each block 83, 84, 85, information relating the time and the displacement amount by the driving means 22 as shown in FIG. 13 and FIG. 14 is tabulated, and each block 83, 84, 85 outputs this tabulated information for each reference time. However, in each of the blocks 83, 84 and 85, information relating the time and the displacement amount by the driving means 22 as shown in FIG. 13 and FIG. 14 is converted into a function and calculated for each reference time. May be configured to output.

  There are as many blocks as the blocks 83, 84, 85 for outputting the displacement amount for each component for each reference time as many as the number of periodic fluctuations to be controlled. For example, such a block may be provided in accordance with fluctuations in the travel of the transfer belt 11 due to detection errors of the encoding roller and fluctuations in the thickness of the transfer belt 11. Each of these blocks outputs information regarding the amount of variation at the reference time for each control period, and the sum of all the position information becomes information regarding the amount of variation by the driving means 22 at that time.

  Each of these pieces of information is unique to the apparatus and has little change with time. Therefore, each piece of information is generated based on measurements performed before shipment and stored in the control means. However, in consideration of the change with time, the above-described encoding roller or the like may be provided, and when the image forming apparatus 1 is used, such data may be generated in a timely manner and used. If the control means controls the drive means 22 in accordance with this information, the periodic fluctuation of each block can be canceled and the transfer belt 11 can travel stably.

  Next, an example of feedback control will be described. As shown in FIG. 16, detection is provided with a lattice-shaped slit pattern 86 disposed on the transfer belt 11 over one circumference of the transfer belt 11 and a sensor 87 as a slit pattern detector for detecting the slit pattern 86. Means 80, a controller 88 that receives data from the sensor 87, and an actuator drive unit 89 that drives the drive means 22 based on control by the controller 88.

  The slit pattern 86 is formed by pasting a member such as a tape (not shown) on which a grid-like slit pattern at equal intervals is printed in advance on the end or back surface of the transfer belt 11 that does not affect image formation. Or by directly printing a grid-like slit pattern on the transfer belt 11 in such a region. Further, the slit pattern 86 may be formed by providing a metal layer such as aluminum on the transfer belt 11, irradiating the laser beam thereon, and sputtering the metal, thereby partially destroying the metal crystal. .

  The former method in which a member on which the slit pattern 86 has been previously formed is attached to the transfer belt 11 is performed by applying a slit at the time of application, such as when the amount of adhesive is uneven or when an air layer is generated during application. The latter method in which the slit pattern 88 is directly formed on the transfer belt 11 is desirable because there is a risk of unevenness in the interval between the patterns 88. The latter method is advantageous in that the slit pattern formation by laser processing can be formed with high accuracy and high resolution.

  The controller 88 and the actuator driving unit 89 are provided in the control means. The slit pattern 88 detected by the sensor 87, that is, data relating to the travel of the transfer belt 11 is sent to the controller 88. In the controller 88, the detected data and the target data are compared, and if there is a difference between them, the displacement amount by the driving means 22 for canceling the difference is calculated using the inclination value as described above. And output to the actuator driver 89. The actuator driving unit 89 drives the driving unit 22 in accordance with the output data regarding the displacement amount.

  As described above, the control unit and the drive unit 22 provide feedback for driving the drive unit 22 so as to cancel out the fluctuation of the transfer belt 11 in the transfer section 25 detected by the detection unit 80, and thereby transfer the transfer belt 11. 11 is eliminated, and the transfer belt 11 is stably driven.

  Such feedforward control and feedback control are performed when the control means drives the drive means 22. Therefore, data necessary for each control, such as a slope value as shown in FIG. 7, is stored in advance in the control means, and is also stored by detection. Feed forward control and feedback control may be used in combination according to the object to be controlled. It is suitable to perform feed-forward control for the amount of fluctuation that is unique to the device and has little change over time, but the information for that is generated based on measurements performed before shipment and stored in the control means It may be a thing, and it may be produced | generated timely using the means to detect such a variation | change_quantity. When a means for detecting the fluctuation amount is provided, feedforward control can be performed using this means.

Now, a specific form of the drive means 22 will be described.
As shown in FIG. 17, the driving means 22 is configured such that the driven roller 19 is displaced as a winding member around which the transfer belt 11 is wound, and the transfer belt 11 is moved to the driven roller 19 as shown in FIG. First, the case where the driven roller 19 is displaced will be described, although it differs depending on whether the guide member 91 as a winding member wound around the same position is displaced.

  As shown in FIG. 17, the driving means 22 is integrated with the guide member 92 by fixing the guide member 92 and sliding the driven roller 19 to displace the driven roller 19. And an actuator 93 to be displaced. Reference numerals 94, 95, and 96 denote bearings, springs, and pedestals, respectively, which are disposed corresponding to the respective ends of the driven roller 19. An arrow indicated by reference numeral 90 in FIG. 17 indicates a direction in which the actuator 93 displaces the driven roller 19.

  The bearing 94 supports each end of the shaft 19 a of the driven roller 19 and plays a role of smoothing the rotation of the driven roller 19. The pedestal 96 is fixed to a housing (not shown) on the image forming apparatus 1 main body side, and the spring 95 is fixed to the bearing 94 and the pedestal 96 at each end. The spring 95 urges the bearing 94 toward the center of the guide member 92 in a range where the guide member 92 contacts the driven roller 19 in the rotational direction of the driven roller 19.

  As shown in FIG. 18, when the transfer belt 11 starts to wind around the driven roller 19 as a point 180, the point away from the driven roller 19 as a point 181 and the rotation center of the driven roller 19 as a point 190, the point 190 and the point An angle 185 sandwiched between a straight line 183 connecting 180 and a straight line 184 connecting point 190 and point 181 is referred to as a winding angle of the transfer belt 11 by the driven roller 19. The driven roller 19 has an eccentricity according to the processing accuracy like the conventional roller. However, the most effective way to suppress the change in the traveling path of the transfer belt 11 due to the eccentricity of the driven roller 19 is to make the belt winding angle 184 equal to the second degree. The change of the position of the outer peripheral surface of the driven roller 19 is controlled at a point 187 where the straight line 186 to be divided and the outer peripheral surface of the driven roller 19 intersect. Therefore, in order to regulate the outer peripheral surface of the driven roller, the guide member 92 is disposed corresponding to the range including this point 186. The direction in which straight line 186 extends is parallel to the direction indicated by arrow 29 in FIG. 16 and the direction indicated by arrow 90 in FIG.

  The spring 95 and the pedestal 96 constitute a pressure system 97 for pressing the driven roller 19 against the guide member 92 via the bearing 94. The bearing 94 is supported by the casing described above with a certain movable range, and is supported by the pressurizing system 97 and the guide member 92. Such a movable range is a range in which the driven roller 19 can move so as to come into contact with the guide member 92 by the pressure system 97, and the outer peripheral portion of the driven roller 19 is positioned by the guide member 92. It is the range which hold | maintains so that it may remove | deviate greatly from the optimal position of these, and it may not drop out.

  The configuration aspects such as the position of the base 96, the position of the spring 95, and the strength of the urging force are changed in the running state of the transfer belt 11 due to an external load applied when the user uses the image forming apparatus 1. Even if this occurs, the driven roller 19 is selected and configured so as not to be detached from the guide member 92. As described above, the pressure applied by the pressure system 97 is configured such that the guide member 92 is always in contact with the driven roller 19 and can reliably perform its function.

  The guide member 92 is disposed corresponding to the non-contact position of the driven roller 19 with the transfer belt 11. That is, the guide member 92 is installed so as to be in contact with the outer peripheral portion of the driven roller 19 at both ends of the driven roller 19 where the transfer belt 11 is not wound. Thus, even if the driven roller 19 has an eccentricity by winding the transfer belt 11 and bringing the guide member 92 into contact with the outer peripheral portion of the driven roller 19, the travel position of the transfer belt 11 is driven by the guide member 92. Variation in the position of the outer peripheral portion of the driven roller 19 that regulates the above is suppressed.

  Further, the actuator 93 displaces the guide member 92 to determine the position of the outer peripheral portion of the driven roller 19, and the travel path length of the transfer belt 11 can be arbitrarily adjusted. Further, by arranging the guide member 92 at the end of the driven roller 19 corresponding to the non-contact position with the transfer belt 11, the guide member 92 does not engage with the transfer belt 11 and acts directly on the transfer belt 11. Therefore, the transfer belt 11 is not damaged or wrinkled. The guide member 92 can also have a function as a member for preventing the transfer belt 11 from meandering.

  As shown in FIG. 19, the contact surface 191 of the guide member 92 that contacts the driven roller 19 has a curved surface shape that has the same curvature as that of the outer surface of the driven roller 19. Therefore, even if the guide member 92 is in contact with the driven roller 19 on the contact surface 191, there is no great resistance when the driven roller 19 rotates.

  The contact surface 191 having such a curved shape has an advantage in improving the wear resistance of the guide member 92. That is, the curved surface shape reduces wear due to contact with the driven roller 19. Therefore, the frequency of replacement caused by wear of the guide member 92 is reduced, and it is possible to prevent a situation in which the frequency of replacement is higher than that of other members.

  As the area of the contact surface 191 is larger, the contact pressure with the driven roller 19 is reduced, and the contact surface 191 is less likely to be worn. However, when the guide member 92 is made of a highly wear-resistant material, The range may be narrow and the resistance may be reduced, whereby the guide member 92 can be miniaturized. The shape of the surface other than the contact surface 191 that does not contact the driven roller 19, for example, the surface indicated by reference numeral 192 in FIG. 19, may be any shape, and is a shape that can be easily fixed to the actuator 93. However, the end of the contact surface 191 in the rotation direction of the driven roller 19 as indicated by reference numerals 193 and 194 in FIG. 19 does not become a large load with respect to the rotation of the driven roller 19 and is a source of scratches and vibrations. Chamfering may be performed so as not to occur.

  The material of the guide member 92, particularly the contact surface 191 portion, is preferably made of a material having a low friction coefficient. In this embodiment, the contact surface 191 is formed by providing a polyacetal (POM) layer. In addition, the layer constituting the contact surface 191 may be polyamide (PA). The contact surface 191 may be formed by applying a fluororesin coating such as polyratrafluoroethylene (PTFE) instead of a layer structure.

  When the main body portion of the guide member 92 and the contact surface 191 portion are made of different materials, the main body portion is made of metal or hard resin in order to ensure the rigidity of the guide member 92 and prevent deformation. Based on this, it is desirable that the contact surface 191 is made of a material having a low friction coefficient. If the rigidity of the entire guide member 92 is low, the travel path length of the transfer belt 11 varies due to the deformation of the guide member 92. However, if the rigidity of the entire guide member 92 can be ensured, these low friction coefficients The guide member 92 may be made of only this material.

Regardless of whether or not the entire guide member 92 is formed of the same material, in order to prevent the deformation of the guide member 92, it is effective to have a shape that ensures rigidity, such as increasing the thickness.
In addition, the deformation | transformation and abrasion which are object here generate | occur | produce within the time which outputs an image. Long-term deformation and wear are acceptable because the effect on the image is negligible. The material of the driven roller 19 is a metal as in the case of a general driven roller.

  As another configuration of the guide member 92, a lubrication method may be used as means for realizing low friction of the contact surface 191. As a generally known lubrication method, there is a method in which a lubricant such as grease is applied to the contact surface 191, but when the lubricant is applied to the contact surface 191, the lubricant is transferred via the driven roller 19. There is a possibility of adhering to the belt 11. When the lubricant adheres to the transfer belt 11, the drive failure of the transfer belt 11 occurs, or the lubricant attached to the transfer belt 11 further adheres to the transfer paper, which adversely affects image formation.

  Therefore, it is desirable to use a method using gas lubrication as the lubrication method. FIG. 20 shows a contact surface 191 that has been subjected to the treatment of the helical bone groove 195 as a gas lubrication treatment section for realizing gas lubrication. The formation mode of the helical bone groove 195 shown in FIG. 20 is an example, and its width, installation interval, inclination, and the like are determined by the rotational speed of the driven roller 19 and the like. By the formation process of the helical bone groove 195, the driven roller 19 is smoothly driven to rotate while being in pressure contact with the guide member 92.

  As another method using gas lubrication, there is a method in which a vent hole as a gas lubrication processing portion communicating with the contact surface 191 is provided in the guide member 92 and air is caused to flow into the contact surface 191 from the back side of the guide member 92. . According to the system using gas lubrication, it is possible to satisfactorily set the travel route of the transfer belt 11 by the driving unit 22 without causing any trouble in image formation.

  As shown in FIG. 21, as another configuration of the guide member 92, the guide member 92 may have a bearing 101 as a bearing structure as means for realizing low friction of the contact surface 191. The bearing 101 is provided as a portion of the guide member 92 that slides on the driven roller 19. The bearing 101 includes a plurality of balls 102 that are in contact with the driven roller 19 and a holder 103 that holds the balls 102 on the main body of the guide member 92. A set of points of the ball 102 that make point contact with the driven roller 19 forms a contact surface 191 that defines a travel path of the transfer belt 11.

In the configuration in which the guide member 92 forms the contact surface 191 with the bearing 101 and contacts the driven roller 19, the contact with the driven roller 19 can be in a very low friction state.
The member that contacts the driven roller 19 in the bearing 101 may be a cylindrical roller that is in line contact with the driven roller 19 instead of the ball 102. The number of the balls 102 and the rollers may be one or more, but when the number is small, for example, when the number is one, the processing accuracy and arrangement accuracy of the balls 102 and the like are large in defining the travel path of the transfer belt 11. In order to exert an influence, processing and arrangement with high accuracy are required. On the other hand, when a plurality of balls or such rollers are used, the contact ratio of each member with respect to the formation of the contact surface 191 is reduced due to contact with the driven roller 19 by a plurality of members as compared to one time. The requirements for accuracy and placement accuracy are reduced.

  As shown in FIG. 22, the actuator 22 includes a stepping motor 111 as a rotational driving means that generates a rotational motion as power for displacing the guide member 19, and a drive conversion that converts the rotational motion generated by the stepping motor 111 into a linear motion. And a mechanism 112. The stepping motor 111 is energized and controlled by a driving unit.

  The drive conversion mechanism 112 is fixed to the shaft 113 of the stepping motor 111 and is rotationally driven by the stepping motor 111, the lead bar 115 as a driven member extending in the direction of the arrow 90, and the lead bar 115. The cam follower 116 that engages the eccentric cam 114 from both sides in the direction indicated by the arrow 90 and the end of the lead bar 115 on the guide member 92 side are fixed to fix the lead bar 115 and the guide member 92. The fixing member 117 wider than the lead bar 115, the slide guide 118 fixed to the image forming apparatus 1 main body side, which supports the lead bar 115 so as to be slidable in the direction of the arrow 90, and the fixing member 117. Is slidably supported in the direction of arrow 90, and is a slide guide fixed to the main body side of the image forming apparatus 1. And a 19. The lead bar 115 is located on the straight line 186 shown in FIG.

  Since the actuator 22 has such a drive conversion mechanism 112, the eccentric cam 114 that is rotationally driven by the rotation of the stepping motor 111 pushes the cam follower 116, and the rotational movement of the stepping motor 111 causes the lead bar 115 to move along the arrow 90. The lead bar 115 is slid in the direction of the arrow 90, the guide member 92 is displaced, the position of the driven roller 119 is displaced, and the traveling position of the transfer belt 11 is defined. It has become.

  The drive conversion mechanism 112 has the following advantages by adopting the eccentric cam 114. That is, the amount of eccentricity of the eccentric cam 114 is adjusted so that, for example, the amount of variation of the guide member 92 is large enough to cancel the variation in travel of the transfer belt 11 caused by the variation in thickness deviation of the transfer belt 11. If one rotation cycle of the stepping motor 111 is made coincident with one rotation cycle of the transfer belt 11, the control operation by the control means is synchronized with the phase relationship such that the rotation of the stepping motor 111 cancels the fluctuation of the travel of the transfer belt 11. It is only necessary to let it run at a constant speed. Therefore, it is possible to easily perform control for canceling one cycle variation. In this case, the stepping motor 111 only needs to be rotationally driven in a fixed direction, and there is no need to rotate forward and reverse, so the burden on the stepping motor 111 is small and efficient.

  FIG. 23 shows another configuration aspect of the drive conversion mechanism 112. The same parts as those in the above-described configuration are given the same reference numerals, and the description thereof is omitted as appropriate. The drive conversion mechanism 112 is integrated with the shaft 113 and is rotated as a rotating member about the shaft 113 by the stepping motor 111. The drive conversion mechanism 112 is a driven member that extends in the direction of the arrow 90 and meshes with the gear 120. A lead gear 121. The fixing member 115 is disposed at the end of the lead gear 121 on the guide member 19 side. The slide guide 118 supports the lead gear 121 so as to be slidable in the arrow 90 direction. The lead gear 121 is located on the straight line 186 shown in FIG.

  Since the actuator 22 has such a drive conversion mechanism 112, the rotational movement of the gear 120 that is rotationally driven by the rotation of the stepping motor 111 is converted into a movement in a direction in which the lead gear 121 slides in the direction of the arrow 90. The lead gear 121 is slid in the direction of the arrow 90, the guide member 92 is displaced, the position of the driven roller 119 is displaced, and the running position of the transfer belt 11 is defined.

  The drive conversion mechanism 112 has the following advantages by adopting a so-called worm gear mechanism having a gear 120 and a lead gear 121. That is, since the feed amount of one rotation of the stepping motor 111 is determined by the lead angle of the worm gear, the feed amount can be set according to the step angle of the stepping motor 111 and the desired control accuracy. Compared with the above-described configuration, the degree of freedom in setting the drive control is high.

  As described above, the drive conversion mechanism 112 uses the eccentric cam 114 and the gear 120 to convert the rotation of the stepping motor 111 into the slide direction and adjust the position of the guide member 92 to a desired position. This method is used in various fields of industry such as stage positioning, and the mechanism can be designed with high rigidity, so that highly accurate control is possible. In addition, the drive conversion mechanism 112 may have other configurations as long as it can move the guide member 92 in the direction of the arrow 90 by a desired amount of displacement. The driving unit 22 may have any configuration as long as it can be moved by the amount of displacement.

  The driving means 22 displaces the guide member 92 and changes the travel path length of the transfer belt 11 with the above-described configuration. However, depending on the configuration of the transfer belt unit 14, that is, depending on the configuration of the endless belt conveyance system. Has the following problems. That is, since the tension of the endless belt is not sufficient, the contact of the endless belt with the winding member to be controlled is weak, and the travel path of the endless belt may not be accurately defined. Further, when the winding member to be controlled moves suddenly and greatly, the tension of the endless belt temporarily rises and falls, so that the endless belt expands and contracts, and the endless belt travel fluctuation may be newly generated. .

  FIG. 24 shows a driving means 22 having a configuration for dealing with such a problem. The drive means 22 has a drive conversion mechanism 112, similar to the drive means 22 shown in FIG. 22. The drive conversion mechanism 112 is the same as the eccentric cam 114 similar to the drive conversion mechanism 112 shown in FIG. However, the piezoelectric element 130 is disposed at a position of the guide member 92 in contact with the fixing member 117. In FIG. 24, the same components as those in the configuration of the drive conversion mechanism 112 shown in FIG.

  The drive conversion mechanism 112 shown in FIG. 24 is arranged in parallel with the direction of the arrow 90, and includes a slide guide 118, a tension spring 122 as an urging means fixed to the lead bar 115, and a slide guide 118. It has a pressed part 123 that is disposed at the end opposite to the side on which the fixing member 117 is fixed and engages with the eccentric cam 114. The tension spring 122 biases the slide guide 118 in the direction of the arrow 90 in the direction in which the pressed portion 123 is pressed against the eccentric cam 114, whereby the pressed portion 123 is biased to the eccentric cam 114. Is always pressed against.

  The piezoelectric element 130 is for detecting the belt tension, and is connected to an amplifier 131 that amplifies the output of the piezoelectric element 130. The amplifier 131 is based on the amplified output of the piezoelectric element 130. The controller 132 is connected to a controller 132 that monitors the tension. The controller 132 is connected to a motor driver 133 that controls the rotation of the stepping motor 111 under the control of the controller 132 in accordance with the tension of the transfer belt 11 monitored by the controller 132. The motor driver 133 is connected to the stepping motor 111. The amplifier 131, the controller 132, and the motor driver 133 are provided in the control means.

  In the controller 132, the tension of the transfer belt 11 is estimated from the output of the piezoelectric element 130 that changes according to the pressing force of the transfer belt 11 to the guide member 92, and the belt tension of the transfer belt 11 is monitored. The tension of the transfer belt 11 is in a range that does not affect the driving of the transfer belt 11 by the drive roller 15, whether the tension is sufficient for running, whether the transfer belt 11 itself is in a range that does not expand and contract. Monitor whether or not. Since the output of the piezoelectric element 130 is directly compared with the value to be taken by the output of the piezoelectric element 130 stored in the controller 132, it is not necessary to convert the output of the piezoelectric element 130 into the tension of the transfer belt 11.

  The controller 132 limits the rotation control amount of the stepping motor 111 and limits the displacement amount of the driven roller 19 by the motor driver 133 while monitoring the output of the piezoelectric element 130. The range that the tension value of the transfer belt 11 should occupy, such as the fluctuation of the tension of the transfer belt 11 in which the expansion and contraction of the transfer belt 11 occurs and the tension of the transfer belt 11 in which the driving amount of the transfer belt 11 by the drive motor 15 fluctuates, is preliminarily set. I can grasp.

  Therefore, when the normal control is performed, if the tension of the transfer belt 11 exceeds such a range, the normal control is limited, and for example, the tension of the transfer belt 11 is such a tension. When it becomes stronger than the range, the driving of the stepping motor 11 in the direction of pulling the guide member 92 is suppressed, and when the tension of the transfer belt 11 becomes weaker than the range, for example, the direction of pushing the guide member 92 The driving of the stepping motor 11 is suppressed. By adopting such a configuration, it is possible to appropriately control the travel path length of the transfer belt 11 while keeping the tension of the transfer belt 11 in an appropriate range.

  As shown in FIG. 25, the drive means 22 has a guide member 91 as a winding member that slidably rubs the transfer belt 11 around the transfer belt 11 in the same position as the driven roller 19. Can do. In this embodiment, the same parts as those described with reference to FIGS. 17 to 24 are denoted by the same reference numerals, and the illustration is omitted, and the description is omitted as appropriate.

  The guide member 91 is fixed to the actuator 93 at both ends of the guide member 91 where the transfer belt 11 is not wound, that is, at a position corresponding to the non-contact position. As shown in FIG. 26, the portion of the guide member 91 that contacts the transfer belt 11 is a contact surface 124 that forms a curved surface with a curvature that allows the transfer belt 11 to move smoothly. The curvature of the portion where the transfer belt 11 starts to contact the guide member 91 may be partially changed, for example, by increasing the curvature so that the transfer belt 11 can easily enter.

  By providing the guide member 91 instead of the driven roller 19, the manufacturing cost such as the cost for manufacturing the driven roller 19 can be significantly reduced while ensuring the function of defining the travel path of the transfer belt 11. Further, since the driven roller 19 is not provided, there is no change in the travel path length of the transfer belt 11 due to the eccentricity, so that the travel path of the transfer belt 11 can be defined with high accuracy.

  The guide member 91 desirably has low friction with respect to the transfer belt 11. Accordingly, the guide member 91 is formed by providing the contact surface 124 with a polyacetal (POM) layer. Alternatively, the layer constituting the contact surface 124 may be polyamide (PA). The contact surface 191 may be formed by applying a fluororesin coating such as polyratrafluoroethylene (PTFE) instead of a layer structure.

  When the main body portion of the guide member 91 and the contact surface 124 are made of different materials, the main body portion is made of metal or hard resin in order to ensure the rigidity of the guide member 91 and prevent deformation. Based on this, it is desirable that the contact surface 124 be made of a material having a low friction coefficient. If the rigidity of the entire guide member 91 is low, the travel path length of the transfer belt 11 may vary due to the deformation of the guide member 91. However, if the rigidity of the entire guide member 91 can be secured, these low friction coefficients. The guide member 91 may be made of only this material.

Regardless of whether or not the entire guide member 91 is formed of the same material, in order to prevent the deformation of the guide member 91, it is effective to have a shape that ensures rigidity, such as increasing the thickness.
In addition, the deformation | transformation and abrasion which are object here generate | occur | produce within the time which outputs an image. Long-term deformation and wear are acceptable because the effect on the image is negligible.

  As another configuration of the guide member 91, a lubrication method may be used as means for realizing low friction of the contact surface 124. The lubrication method may be a method of forming a gas lubrication processing unit similar to that described above. As another configuration of the guide member 91 as shown in FIG. 27, the guide member 91 may have a bearing 125 as a bearing structure as means for realizing low friction of the contact surface 124. The bearing 125 is provided as a portion of the guide member 91 that slides on the transfer belt 11. The bearing 125 includes a plurality of balls 126 that come into contact with the transfer belt 11, and a holder 127 that holds the balls 126 on the main body of the guide member 91. A set of points of the ball 126 that make point contact with the transfer belt 11 forms a contact surface 124 and defines a travel path of the transfer belt 11.

In the configuration in which the guide member 91 forms the contact surface 124 with the bearing 125 and abuts against the transfer belt 11, the contact with the transfer belt 11 is in a very low friction state, and the conveyance resistance of the transfer belt 11 is reduced. Can do.
The member that contacts the transfer belt 11 in the bearing 125 may be a cylindrical roller that makes line contact with the transfer belt 11 instead of the ball 126. The number of the balls 126 and the rollers may be one or more. However, when the number is small, for example, when the number is one, the processing accuracy and arrangement accuracy of the balls 126 and the like are large in defining the travel path of the transfer belt 11. In order to exert an influence, processing and arrangement with high accuracy are required. On the other hand, when a plurality of balls or such rollers are used, a plurality of members abut against the transfer belt 11 and the contribution ratio of each member to the formation of the contact surface 124 is reduced as compared with one case. The requirements for accuracy and placement accuracy are reduced.

  FIGS. 28 to 30 show examples of the actuator 93 and the like of the drive means 22 provided with the guide member 91. The configuration examples of the actuator 93 and the like shown in FIGS. 28 to 30 are the same as the configuration examples of the actuator 93 and the like shown in FIGS. 22 to 24. Therefore, the configuration of the actuator 93 and the like shown in FIGS. The same reference numerals are given to the same parts as in the example, and the description is omitted.

As described above, as a mode for carrying out the present invention, the belt travel stabilization device 21 to which the present invention is applied, and the belt travel stabilization device 21 and the image forming apparatus 1 having the endless belt as the transfer belt 11 as a conveying member. As described above, the image forming apparatus to which the present invention is applied may have an endless belt as an image carrier such as a photosensitive belt or an intermediate transfer member such as an intermediate transfer belt. In this case, the above-described transfer belt 11 can be used as an image carrier and an intermediate transfer member, and the present invention can be similarly applied. It is provided as a forming section, and is provided as a transferring section in the intermediate transfer member.
When the endless belt is used as an image carrier, in such an image forming section, the image carrier is cleaned as a photoconductor cleaning device as provided in the above-described image forming unit as an image forming unit facing the image carrier. A means, a charge eliminating means, a charging means, a developing means and the like are appropriately provided.

The guide member has been disposed corresponding to the non-contact position with the endless belt, but may be disposed corresponding to the contact position with the endless belt.
The belt running stabilization device to which the present invention is applied is not limited to an image forming apparatus as long as it is an apparatus using an endless belt, and can be mounted on any apparatus.
The application of the present invention is not limited to the above-described embodiment unless particularly limited in the above description.

1 is a front view schematically showing an image forming apparatus to which the present invention is applied. FIG. 2 is a front view showing an image forming unit and a transfer belt unit mounted on the image forming apparatus shown in FIG. 1. FIG. 3 is a conceptual diagram illustrating how a travel path length of a transfer belt provided in the transfer belt unit illustrated in FIG. 2 varies due to a variation in a position of a member around which the transfer belt is wound. It is a conceptual diagram for demonstrating the arrangement | positioning position of the member which should be displaced in order to control the fluctuation | variation of a driving | running | working in each area of the endless belt wound around the several member. It is a conceptual diagram which models and demonstrates the relationship between the travel path length of an endless belt, and the displacement amount of one of the two adjacent members which wound the endless belt. FIG. 6 is a conceptual diagram that expands the model shown in FIG. 5 and models and explains the relationship between the travel path length of the endless belt and the displacement amount of the central member among the three adjacent members wound around the endless belt. is there. FIG. 6 is a correlation diagram showing the relationship between the travel path length of the endless belt and the displacement amount of the central member among the three adjacent members wound around the endless belt when the model shown in FIG. 6 has a certain size. It is. It is a conceptual diagram which models and demonstrates the relationship between the fluctuation | variation of the thickness of an endless belt, and the travel speed of an endless belt. It is a front view which shows the structural example for performing the feedforward control which detects the change of a driving | running | working of an endless belt, and stabilizes driving | running | working of an endless belt. FIG. 5 is a correlation diagram between a change in travel of an endless belt and time detected using a predetermined detection unit. It is the correlation diagram which extracted and showed the rotation period component of the endless belt included in the change of driving | running | working of the endless belt shown in FIG. It is the correlation diagram which extracted and showed the rotation period component of the drive member included in the change of a driving | running | working of an endless belt shown in FIG. FIG. 12 is a correlation diagram between a control amount of a member around which the endless belt is wound and time for canceling the rotation period component of the endless belt shown in FIG. 11. FIG. 13 is a correlation diagram between a control amount of a member wound with an endless belt and time for canceling a rotation period component of the driving member shown in FIG. 12. FIG. 5 is a conceptual diagram showing that the sum of the component amounts, which should displace a member around which the endless belt is wound, becomes a control amount by the driving means in order to cancel fluctuations in the travel of the endless belt. It is a front view which shows the structural example for performing the feedback control which detects the change of a driving | running | working of an endless belt, and stabilizes driving | running | working of an endless belt. 1 is a perspective view showing a schematic configuration of a belt running stabilization device to which the present invention is applied. It is a front view which shows the arrangement | positioning aspect of the guide member with which the belt running stabilization apparatus shown in FIG. 17 was equipped. It is a perspective view of the guide member shown in FIG. It is the schematic which shows the gas lubrication process part formed in the surface which rubs against the other member of the guide member shown in FIG. It is the schematic which shows the bearing structure arrange | positioned in the part which rubs against the other member of the guide member shown in FIG. It is a front view explaining an example of the drive means with which the belt running stabilization apparatus shown in FIG. 17 was equipped. It is a front view explaining the other example of the drive means with which the belt running stabilization apparatus shown in FIG. 17 was equipped. FIG. 18 is a front view showing a schematic configuration of another example of the driving means provided in the belt running stabilization device shown in FIG. 17 and provided with a detecting means for detecting the tension of the endless belt. It is a perspective view which shows the guide member which wound the endless belt. FIG. 26 is a schematic front view showing the guide member shown in FIG. 25 and driving means including the guide member. It is the schematic which shows the bearing structure arrange | positioned in the part which rubs against the other member of the guide member shown in FIG. It is a front view explaining an example of the drive means provided with the guide member shown in FIG. It is a front view explaining the other example of the drive means provided with the guide member shown in FIG. FIG. 27 is a front view showing a schematic configuration of another example of the driving unit including the guide member illustrated in FIG. 26 and including a detection unit that detects the tension of the endless belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Endless belt 11, 24, 411 Endless belt 15, 23, 415 Driving member 18, 19, 402, 403, 418, 419 Rolling member 18, 19, 91, 402 , 403, 418, 419 Winding member 22 Drive means 25 Predetermined section 91 Winding member 91, 92 guide member 101, 125 which is a guide member Bearing structure 111 Rotation drive means 112 Drive conversion mechanism 114 Eccentric cam 115, 121 Driven Member 120 Rotating member 124, 191 Surface of guide member that rubs against other member 195 Gas lubrication processing unit 130 Detection means

Claims (19)

A winding member around which an endless belt is wound;
Driving means for displacing the winding member in order to cancel the fluctuation of the traveling speed in a predetermined section of the endless belt;
A tension applying member that applies a predetermined tension to the endless belt;
A driving member for winding the endless belt together with the winding member at a position different from the predetermined section, and driving the endless belt to rotate;
The amount of change in the travel path length from the drive member of the endless belt to the predetermined section is determined by the amount of displacement of the winding member, and the travel speed of the endless belt in the predetermined section by the amount of change in the travel path length. There by utilizing the change, the displacement of the winding member by the drive means, and control means for controlling so as to cancel the variation of the running speed in the predetermined interval,
The winding member winds the endless belt between the position where the driving member winds the endless belt and the predetermined section,
Traveling in the predetermined section which is predicted based on the profile of the thickness variation of the fluctuation amount or an endless belt running speed in sensed the predetermined interval by the detection means for detecting the variation of the running speed of the endless belt based on the amount of fluctuation of the speed, determine the amount of displacement of the winding members to cancel the variation of the running speed in the predetermined interval, the tension by displacing the winding member by said driving means on the basis of the displacement amount A belt travel stabilization device that cancels fluctuations in the travel speed of the endless belt in the predetermined section by changing the travel path of the endless belt while maintaining the tension of the endless belt at a predetermined tension by the applying member. In the belt running stabilization device according to claim 1,
The belt travel stabilization device, wherein the driving means includes a guide member for sliding the winding member to displace the winding member.   3. The belt travel stabilization device according to claim 2, wherein the guide member is disposed corresponding to a non-contact position of the winding member with the endless belt.   4. The belt travel stabilization device according to claim 2, wherein the winding member is a rotating body that rotates following the endless belt.   2. The belt travel stabilization device according to claim 1, wherein the winding member is a guide member that slides on the endless belt.   6. The belt running stabilization device according to claim 2, wherein a surface of the guide member that slides on another member has a curved surface with a predetermined curvature. Device.   7. The belt travel stabilization apparatus according to claim 2, wherein the entire guide member is formed using a material having a low friction coefficient.   The belt running stabilization device according to any one of claims 2 to 6, wherein a surface of the guide member that slides on another member is formed using a material having a low friction coefficient. Belt running stabilization device.   9. The belt travel stabilization apparatus according to claim 2, wherein a surface of the guide member that engages with another member has a gas lubrication processing section. apparatus.   9. The belt travel stabilization device according to claim 2, wherein a portion of the guide member that engages with another member has a bearing structure. 11. The belt travel stabilization device according to claim 1, wherein the driving means generates a rotational motion, and a drive conversion for converting the rotational motion by the rotational driving means into a linear motion. belt traveling stabilizer, characterized by chromatic and mechanism.   12. The belt travel stabilization device according to claim 11, wherein the drive conversion mechanism is driven in a linear direction by an eccentric cam that is rotationally driven by the rotational drive means and a rotation of the eccentric cam that is engaged with the eccentric cam. A belt running stabilization device comprising a driven member.   12. The belt travel stabilization device according to claim 11, wherein the drive conversion mechanism is a driven member that is driven in a linear direction by rotation of a rotating member that is rotationally driven by the rotational driving means, and that is engaged with the rotating member. And a belt running stabilization device.   14. The belt travel stabilization device according to claim 1, further comprising a detection unit that detects a tension of an endless belt wound by the winding member that is displaced by the driving unit. A belt running stabilization device characterized in that the means limits the amount of displacement of the winding member by the driving means in accordance with the tension of the endless belt detected by the detecting means.   The belt travel stabilization device according to any one of claims 1 to 14, an endless belt wound around the winding member, and the endless belt around which the endless belt is wound together with the winding member. An image forming apparatus having a driving member for driving.   16. The image forming apparatus according to claim 15, wherein the endless belt is used as a conveying member for conveying a recording medium in the predetermined section.   16. The image forming apparatus according to claim 15, wherein the endless belt is used as an image carrier.   18. The image forming apparatus according to claim 17, further comprising image forming means for holding an image on the endless belt in the predetermined section.   16. The image forming apparatus according to claim 15, wherein the endless belt is used as an intermediate transfer member to which an image is transferred in the predetermined section.

Images