JP4530281B2 - Rotary encoder, roller member, belt conveyance device, and image forming apparatus - Google Patents

Description

  The present invention relates to a rotary encoder that detects fluctuations in the rotation speed and rotation angle of a roller member, and a roller member, a belt conveyance device, and an image forming apparatus including the rotary encoder.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, a technique that uses a rotary encoder to detect a change in rotational speed or rotational angle of a roller member around which a belt member is wound. Is known (for example, see Patent Document 1).

  Specifically, in Patent Document 1 and the like, an encoder sensor in which a code wheel is integrally installed on a shaft portion of a roller member (conveying roller) and detects slits formed radially on the main surface of the code wheel is an image forming apparatus. It is installed on the main body side of the (recording device). Then, the fluctuation of the rotation speed or the rotation angle of the roller member is determined based on the fluctuation of the interval of the pulse signal obtained by converting the output of the encoder sensor (the output signal obtained by optically detecting the presence or absence of the slit). Thus, the drive control of the roller member (feedback control) is performed to stabilize the rotational drive of the roller member.

  On the other hand, Patent Document 2 and the like disclose a rotary encoder that is integrally installed on a shaft portion (rotating shaft). Specifically, a code wheel (rotary plate) is fixed to the shaft portion via a support member (fixed plate). Around the code wheel, a case (front case, rear case) that can be divided in the axial direction is disposed on the shaft portion. A light emitting element of the encoder sensor is fixed to one of the two cases that can be divided, and a light receiving element of the encoder sensor is fixed to the other.

JP 2002-248822 A No. 7-5373

  In the conventional rotary encoder described above, it is difficult to reduce the size of the code wheel by reducing the thickness.

  That is, if the code wheel can be made thinner, other members such as a transmission type photosensor (encoder sensor) that sandwiches a part of the outer periphery of the code wheel can be reduced in size, and the entire rotary encoder can be reduced in size. However, when the code wheel is made of a flexible material such as PET (polyethylene terephthalate) and thinned, if the code wheel is fixed directly to the shaft portion of the roller member, the code wheel is bent and its posture is changed. There was a problem that it could not be determined. In such a case, the original function of the rotary encoder cannot be exhibited, and the drive control of the roller member may become unstable.

On the other hand, in Patent Document 2 and the like, since the support member (fixed plate) to which the code wheel (rotary plate) is stuck is press-fitted into the shaft portion of the roller member, the code wheel is thinned (rotary encoder). The effect of achieving downsizing) can be expected.
However, when a support member made of a resin material or the like is press-fitted into a shaft portion made of a metal material or the like, shaving powder is generated from the inner diameter portion of the support member, and the shaving powder adheres to the support member that adheres the code wheel. There was a possibility that defects accumulated on the surface could occur.

  Specifically, with reference to FIG. 9, the code wheel 50 is fixed on the opposite side (right side) of the press-fitting direction of the support member 71 with respect to the shaft portion 47b (on the left side in FIG. 9). Therefore, when the support member 71 is press-fitted into the shaft portion 47b, the shaving powder K generated at the time of press-fitting moves to the fixing surface side of the code wheel 50 (the side opposite to the press-fitting direction). Then, the moved cutting powder K accumulates on the fixed surface (sticking surface) of the code wheel 50 and pushes up the central portion of the code wheel 50 (the state shown in FIG. 9).

  In such a case, the deformation of the central portion of the code wheel 50 may reach the outer peripheral portion. That is, the outer peripheral part in which the slit 50a is formed may be deformed (the state shown in FIG. 9). The phenomenon that the slit 50a is deformed in accordance with the deformation of the central portion of the code wheel 50 as described above is often observed particularly in the rotary encoder in which the code wheel 50 is reduced in diameter (miniaturized). When the slit 50a is deformed, the rotation state of the code wheel 50 (or the roller member) cannot be accurately detected by the encoder sensor, and the drive control of the roller member becomes unstable. .

  The present invention has been made to solve the above-described problems. Even when the code wheel is thinned and reduced in diameter, the code wheel fixed to the shaft portion of the roller member is deformed. It is an object of the present invention to provide a rotary encoder, a roller member, a belt conveyance device, and an image forming apparatus with high detection reliability.

The rotary encoder according to the first aspect of the present invention includes a support member that is press-fitted into the shaft portion of the roller member and rotates together with the shaft portion, and is fixed to the support member and rotates together with the support member. A code wheel, wherein the code wheel is fixed to the support member apart from a press-fitting region into which the support member is press-fitted , and the shaft portion has a press-fitting region with respect to a shaft diameter in the press-fitting region. And a shaft diameter in a region between the code wheel and the fixed position of the code wheel .

A rotary encoder according to a second aspect of the present invention is the rotary encoder according to the first aspect, wherein the support member is fixed to the press-fitted region and the code wheel with respect to the hole diameter in the press-fitted region. Is formed so that the hole diameter in the region between the two becomes larger.

According to a third aspect of the present invention, in the rotary encoder according to the first or second aspect of the present invention, the code wheel is fixed to a side opposite to the press-fitting direction of the support member with respect to the shaft portion. Is.

According to a fourth aspect of the present invention, in the rotary encoder according to the first aspect of the present invention, the code wheel is attached to one end face of the support member with a double-sided tape. Is.

A rotary encoder according to a fifth aspect of the present invention is the rotary encoder according to any one of the first to fourth aspects, wherein the code wheel is made of a flexible material.

According to a sixth aspect of the present invention, in the rotary encoder according to any one of the first to fifth aspects, the support member has an area of a surface on which the code wheel is fixed. It is formed to be smaller than the area of the main surface.

According to a seventh aspect of the present invention, in the rotary encoder according to any one of the first to sixth aspects, the support member abuts against a step provided in the shaft portion and is axial. The press-fitting position of is determined.

A rotary encoder according to an eighth aspect of the present invention is the rotary encoder according to any one of the first to seventh aspects of the present invention, relative to the shaft portion via a bearing inserted into the shaft portion. And a cover that covers the code wheel together with the support member, and an encoder sensor that is installed in the cover and detects the rotation of the code wheel.

According to a ninth aspect of the invention, in the rotary encoder according to the eighth aspect of the invention, the cover is provided with one of the bearings and is cantilevered on the shaft portion.

According to a tenth aspect of the present invention, in the rotary encoder according to the eighth aspect or the ninth aspect, the cover and the support member are formed so that opposing surfaces thereof are nested. It is a thing.

The rotary encoder according to an eleventh aspect of the present invention is the rotary encoder according to any one of the eighth to tenth aspects, wherein the cover is arranged such that the fixed position of the encoder sensor is above the gravitational direction. It is fixedly supported.

A rotary encoder according to a twelfth aspect of the present invention is the rotary encoder according to any of the eighth to eleventh aspects, wherein the encoder sensor is inserted into a part of the outer periphery of the code wheel. The transmissive photosensor is provided.

A rotary encoder according to a thirteenth aspect of the present invention is the rotary encoder according to any one of the eighth to twelfth aspects, wherein the encoder sensor is installed on the cover using a resin rivet. .

According to a fourteenth aspect of the present invention, in the rotary encoder according to any one of the eighth to thirteenth aspects, the cover is configured such that the bearing abuts against a retaining ring installed on the shaft portion. Thus, an axial position toward the support member is determined.

Further, a rotary encoder according to the invention of claim 15, wherein, in the invention described in any one of the claims 8 to claim 14, wherein the cover is rotated by the engagement member engaged to the cover locking And is urged toward the support member.

According to a sixteenth aspect of the present invention, a roller member according to the sixteenth aspect is obtained by integrally installing the rotary encoder according to any one of the first to fifteenth aspects on the shaft portion.

According to a seventeenth aspect of the present invention, there is provided a belt conveying apparatus including the roller member according to the sixteenth aspect and a belt member wound around a part of the outer peripheral surface of the roller member.

According to an eighteenth aspect of the present invention, in the belt conveying apparatus according to the seventeenth aspect, the belt member is any one of a transfer belt, an intermediate transfer belt, and a photosensitive belt.

An image forming apparatus according to a nineteenth aspect includes the roller member according to the eighteenth aspect.

According to a twentieth aspect of the present invention, an image forming apparatus includes the belt conveying device according to the seventeenth or eighteenth aspect.

  The present invention is configured such that the code wheel is fixed to the support member away from the press-fitting region. As a result, even when the code wheel is made thinner and smaller in diameter, the code wheel fixed to the shaft portion of the roller member via the support member is not deformed, and a rotary with high detection reliability. An encoder, a roller member, a belt conveyance device, and an image forming apparatus can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a configuration diagram illustrating the entire image forming apparatus according to the first embodiment.
In FIG. 1, 1 is a main body of a color printer as an image forming apparatus, 2 is an optical unit (writing unit) that emits laser light based on image information, and 20Y, 20M, 20C, and 20BK are colors (yellow, magenta, Cyan, black), 21 is a photosensitive drum housed in each of the process cartridges 20Y, 20M, 20C, and 20BK, 22 is a charging unit that charges the photosensitive drum 21, and 23 is a photosensitive drum 21. A developing unit that develops the electrostatic latent image formed thereon, 24 is a transfer roller that contacts the inner peripheral surface of the transfer belt 40, 25 is a cleaning unit that collects untransferred toner on the photosensitive drum 21, and 30 is a photosensitive unit. A transfer belt unit as a belt conveying device including a transfer belt 40 for transferring a toner image formed on the body drum 21 to the transfer material P. G, 32Y, 32M, 32C, and 32BK are toner supply units that supply the respective color toners to the developing units 23 of the process cartridges 20Y, 20M, 20C, and 20BK, and 61 is a supply that stores a transfer material P such as transfer paper. A paper portion 66 is a fixing portion for fixing an unfixed image on the transfer material P.

  Here, in each process cartridge 20Y, 20M, 20C, and 20BK, image forming members such as the photosensitive drum 21, the charging unit 22, the developing unit 23, and the cleaning unit 25 are integrally held. Then, image formation of each color (yellow, magenta, cyan, black) is performed on the photosensitive drum 21 in each of the process cartridges 20Y, 20M, 20C, and 20BK.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
Each of the four photosensitive drums 21 rotates in the clockwise direction in FIG. First, the surface of the photosensitive drum 21 is uniformly charged at a position facing the charging unit 22 (a charging process). Thereafter, the surface of the photosensitive drum 21 on which the charged potential is formed reaches the irradiation position of each laser beam.

  On the other hand, in the optical unit 2, laser light corresponding to the image signal is emitted from the LD light source corresponding to each color. The laser light is incident on the polygon mirror 3 and reflected, and then passes through the lenses 4 and 5. The laser light after passing through the lenses 4 and 5 passes through different optical paths for each color component of yellow, magenta, cyan, and black (this is an exposure process).

The laser beam corresponding to the yellow component is reflected by the mirrors 6 to 8 and then irradiated onto the surface of the photosensitive drum 21 of the first process cartridge 20Y from the right side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 21 by the polygon mirror 3 that rotates at high speed. Thus, an electrostatic latent image of a yellow component is formed on the photosensitive drum 21 charged by the charging unit 22.
Similarly, the laser beam corresponding to the magenta component is reflected by the mirrors 9 to 11 and then irradiated to the surface of the photosensitive drum 21 of the second process cartridge 20M from the right side of the sheet, so that an electrostatic latent image of the magenta component is formed. It is formed. The laser beam corresponding to the cyan component is reflected by the mirrors 12 to 14 and then irradiated to the surface of the photosensitive drum 12 of the third process cartridge 20C from the right side of the paper, thereby forming an electrostatic latent image of the cyan component. . The laser beam corresponding to the black component is reflected by the mirror 15 and then irradiated onto the surface of the photosensitive drum 21 of the fourth process cartridge 20BK from the right side of the paper, thereby forming an electrostatic latent image of the black component.

Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent images of the respective colors are formed further rotates and reaches a position facing the developing unit 23. Then, the toner of each color is supplied from the developing unit 23 onto the photosensitive drum 21, and the latent image on the photosensitive drum 21 is developed (this is a developing step).
Thereafter, the surface of the photosensitive drum 21 after the development process reaches a position facing the transfer belt 40 (belt member). Here, the transfer roller 24 is installed at each facing position so as to contact the inner peripheral surface of the transfer belt 40. Then, the toner images of the respective colors formed on the photosensitive drum 21 are sequentially transferred onto the transfer material P conveyed by the transfer belt 40 at the position of the transfer roller 24 (transfer process).

  Here, the transfer belt 40 is stretched and supported by a driving roller and a plurality of driven rollers. Then, the transfer belt 40 travels in the direction of the arrow in the drawing by the driving roller. The transfer belt unit 30 (belt conveying device) including the transfer belt 40 will be described in detail later.

Then, the surface of the photosensitive drum 21 after the transfer process reaches a position facing the cleaning unit 25. The untransferred toner remaining on the photosensitive drum 21 is collected by the cleaning unit 25 (this is a cleaning process).
Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes is completed.

On the other hand, the material to be transferred P fed by the paper feed roller 62 is guided from the paper feed unit 61 to the position of the registration roller 64 after passing through the conveyance guide 63. The transfer material P guided to the registration roller 64 is transported toward the contact portion between the transfer belt 40 and the suction roller 27 while the transport timing is controlled.
Thereafter, the transfer material P sequentially passes through the positions facing the four photosensitive drums 21 while being conveyed to the transfer belt 40 that runs in the direction of the arrow in the drawing. Thus, the toner images of the respective colors are transferred onto the transfer material P, and a color image is formed.

Thereafter, the transfer material P on which the color image is formed is separated from the transfer belt 40 and guided to the fixing unit 66. In the fixing unit 66, the color image is fixed on the transfer material P at the nip portion between the heating roller 67 and the pressure roller 68.
Then, the transfer material P after the fixing process is discharged out of the apparatus main body 1 as an output image by a paper discharge roller 69.
Thus, a series of image forming processes is completed.

Next, referring to FIG. 2, a process cartridge as an image forming unit in the image forming apparatus main body 1 will be described in detail.
The four process cartridges and the toner supply unit installed in the apparatus main body 1 have substantially the same structure except that the color of the toner T to be stored is different. Therefore, the alphabets (Y, M, C, BK) are used. The figure is divided.

  As shown in the figure, in the process cartridge 20, a photosensitive drum 21, a charging unit 22, a developing unit 23, and a cleaning unit 25 are mainly housed in a case 26. The developing unit 23 includes a developing roller 23a, two stirring rollers 23b and 23c, a doctor blade 23d, a toner concentration sensor 29, and the like, and a developer composed of carrier C and toner T is accommodated therein. Yes. The cleaning unit 25 includes a cleaning blade 25a that contacts the photosensitive drum 21 and a cleaning roller 25b.

The image forming process described above will be described in more detail.
The developing roller 23a rotates in the direction of the arrow in the figure. The toner T in the developing unit 23 is mixed with the carrier C together with the toner T supplied from the toner supply unit 32 by the stirring rollers 23b and 23c that rotate counterclockwise in the drawing. The frictionally charged toner T is supplied onto the developing roller 23a together with the carrier C by one stirring roller 23b.
The toner T in the toner bottle 33 is appropriately supplied into the developing unit 23 from the supply port 26a as the toner T in the developing unit 23 is consumed. Consumption of the toner T in the developing unit 23 is detected by a toner concentration sensor 29 (magnetic permeability sensor) provided in the developing unit 23.

Thereafter, the toner T carried on the developing roller 23a passes through the position of the doctor blade 23d and then reaches the position facing the photosensitive drum 21 (developing area). At the opposite position, the toner T adheres to the electrostatic latent image formed on the surface of the photosensitive drum 21. Specifically, the toner T adheres to the surface of the photosensitive drum 21 by an electric field formed by a potential difference between the latent image potential in the region irradiated with the laser light L and the developing bias applied to the developing roller 23a.
Most of the toner T adhering to the photosensitive drum 21 is transferred onto the transfer material P. The toner T remaining on the photosensitive drum 21 is collected in the cleaning unit 25 by the cleaning blade 25a and the cleaning roller 25b.

Next, the configuration and operation of the transfer belt unit 30 including the rotary encoder, which is characteristic in the first embodiment, will be described with reference to FIGS.
FIG. 3 is a cross-sectional view showing a transfer belt unit 30 as a belt conveying device. 4 is a cross-sectional view of the driven roller 47 as a roller member installed in the transfer belt unit 30 of FIG. 3 as viewed in the axial direction.

  As shown in FIG. 3, the transfer belt unit 30 includes a transfer belt 40 as a belt member, a drive roller 44 that stretches and supports the transfer belt 40, a plurality of driven rollers 45 to 49, a drive motor 41, and the like. The The driving force of the driving motor 41 is transmitted to the driving roller 44 via the driving belt 42. When the driving roller 44 is driven to rotate counterclockwise, the transfer belt 40 wound around a part of the outer peripheral surface of the driving roller 44 travels in the direction of the arrow in the figure. Each of the plurality of driven rollers 45 to 49 abuts on the transfer belt 40 traveling in the direction of the arrow and rotates (driven) in the counterclockwise direction.

  Here, of the plurality of driven rollers 45 to 49, one driven roller 47 (roller member) is integrally provided with a rotary encoder. Referring to FIG. 4, driven roller 47 as a roller member includes a roller main portion that abuts on transfer belt 40 and shaft portions 47 a to 47 c. Bearings 70 are respectively inserted into shafts at both ends of the driven roller 47, and the driven roller 47 is supported by the unit body via the bearing 70. Three shaft portions 47a to 47c having different outer diameters are formed on one side of the driven roller 47 (the side where the rotary encoder is installed). The driven roller 47 can be formed of stainless steel or the like.

Referring to FIG. 4, the rotary encoder includes a code wheel 50, a transmissive photosensor 51 as an encoder sensor, a support plate 71 as a support member, a cover 73, and the like.
The support plate 71 is made of a resin material such as polyacetal, and is press-fitted (lightly press-fitted) into the shaft portion 47 b of the driven roller 47. The position of the support plate 71 in the axial direction is determined by coming into contact with a step formed by the two shaft portions 47b and 47c having different outer diameters. Thereby, the positioning accuracy of the support plate 71 on which the code wheel 50 is fixed is improved.

  A code wheel 50 is attached (fixed) to one end face of the support plate 71 (the side opposite to the press-fitting direction) via a double-sided tape 72 (see FIG. 7). The code wheel 50 is made of a flexible material such as PET (polyethylene terephthalate) having a thickness of about 0.2 mm, and radial slits (code portions) 50a are formed on the outer peripheral side of the main surface (see FIG. 5). That is, on the code wheel 50, light transmitting regions and light non-transmitting regions 50a are alternately formed radially. The slit 50a of the code wheel 50 can be formed using, for example, a pattern drawing technique using a photoresist. Then, the photo sensor 51 detects the slit 50a on the code wheel 50, so that the driven roller 47 in which the code wheel 50 (support plate 71) is integrally installed is rotated (rotational speed variation and rotational angle variation). )).

  That is, the code wheel 50 is disposed such that a part of the outer periphery thereof is sandwiched between the light emitting part (light emitting element) 51a and the light receiving part (light receiving element) 51b of the transmissive photosensor 51 (FIG. 5). When the slit 50a (black part) is interposed between the light receiving unit 51a and the light emitting unit 51a, the light output from the light emitting unit 51a is not received and the output becomes high. When the slit 50a (black part) is not interposed, the light emitted from the light emitting part 51a is received and the output becomes low. Therefore, referring to FIG. 6, the rotation of the driven roller 47 (or the code wheel 50) is detected based on the waveform interval of the encoder output signal (the signal after the output of the photosensor 51 is converted). .

  Specifically, when the waveform interval of the encoder output signal is small (in the region A in FIG. 6), the controller 80 recognizes that the driven roller 47 (or the code wheel 50) has a high rotational speed. When the waveform interval of the encoder output signal is large (in the region B in FIG. 6), the controller 80 recognizes that the driven roller 47 (or the code wheel 50) has a low rotation speed. Referring to FIG. 3, information related to the rotation of the driven roller 47 recognized by the control unit 80 is fed back to the drive motor 41. That is, when the controller 80 determines that the rotation speed of the driven roller 47 is slow, the drive speed of the drive motor 41 is accelerated, and when it is determined that the rotation speed of the driven roller 47 is high, the drive motor 41 The drive speed of 41 is decelerated. Thus, the running speed of the transfer belt 40 in the transfer belt unit 30 is stabilized, and problems such as color misregistration of a color toner image formed by superimposing a plurality of color toners are suppressed.

Further, as described above, since the code wheel 50 is formed of a flexible material, even when the code wheel 50 contacts the transmissive photo sensor 51, the photo sensor 51 and the code wheel 50 themselves are damaged. Is suppressed.
Referring to FIG. 4, the area of the contact surface (fixed surface) of support plate 71 to which code wheel 50 is attached is smaller than the area of code wheel 50 (the area of the main surface). Is formed. As a result, the transmission sensor 51 can be installed so as to sandwich a part of the outer periphery of the code wheel 50.

  A cover 73 is rotatably supported on the shaft 47 a of the driven roller 47 via a bearing 74. The bearing 74 is a ball bearing, and an outer diameter portion (outer ring portion) thereof is press-fitted into a hole portion of the cover 73, and an inner diameter portion (inner ring portion) is inserted into the shaft portion 47a. The cover 73 in which the bearing 74 is integrated is inserted from the right side of FIG. 4 with respect to the driven roller 47, and the bearing 74 comes into contact with a retaining ring 75 installed on the shaft portion 47a (the support plate 50). Is the position in the axial direction toward).

  The axial backlash of the cover 73 is removed by the engaging member 86 fixed to the unit side plate 85 of the transfer belt unit 30. Specifically, the engaging member 86 is made of a resin material and engages with an end portion of the cover 73 after being inserted into the shaft portion 47a. More specifically, the protrusion 73a of the cover 73 engages with a groove provided in the inner diameter portion of the engaging member 86, whereby the rotation of the cover 73 is locked. Further, the engagement member 86 urges the cover 73 toward the support plate 71, so that the backlash in the axial direction of the cover 73 is removed. In this way, the positional accuracy between the photosensor 51 held by the cover 73 and the support plate 71 is increased, and the problem of contact between both members is suppressed.

  Here, the cover 73 is cantilevered on the shaft portion 47 a via one bearing 74. As a result, the number of parts is reduced and the size in the axial direction is reduced as compared with the conventional cover configuration supported on the shaft portion via a plurality of bearings.

Further, the end of the cover 73 (the end on the left side in FIG. 4) is an opening, and the support plate 71 is disposed so as to enter the opening with a slight gap. As a result, the periphery of the light emitting portion 51a and the light receiving portion 51b of the code wheel 50 and the photosensor 51 is sealed by the support plate 71 and the cover 73, and foreign matters such as toner, paper dust, belt powder, etc. In addition, problems that adhere to the photosensor 51 are suppressed.
Further, according to the configuration of the first embodiment, the bearing 73 is not installed on the inner side in the axial direction of the cover 73 (the position where the support plate 71 is disposed), and therefore, particularly in the vicinity thereof. The bearing is not locked by the foreign matter. On the other hand, a bearing 74 is installed outside the cover 73 in the axial direction. The bearing 74 is disposed inside the cover 73 and is also covered by the engaging member 86. Defects that foreign matter enters are suppressed.

  The support plate 71 that rotates together with the driven roller 47 and the code wheel 50 and the cover 73 that is fixed in a non-rotating manner are configured such that the opposing surfaces are slightly separated from each other in order to suppress mutual contact friction. Has been. In the first embodiment, the opposing surfaces of the support plate 71 and the cover 73 are formed in a nested manner so that minute foreign matter such as toner does not enter from the gap between the opposing surfaces. Specifically, as shown in FIG. 4, a nest part 71 a (step part) is provided on the outer periphery of the support plate 71, and the nest part (step part) corresponding to the nest part 71 a is disposed on the cover 73 side. Is also provided. This makes it difficult for foreign matter outside the cover 73 to enter the cover 73. In addition, the shape of the support plate 71 and the nesting portion (the nesting-like facing surface) of the cover 73 is not limited to that of the first embodiment. For example, a recess is provided on the outer periphery of the support plate 71, A convex portion corresponding to the concave portion can also be provided on the cover 73 side.

  Referring to FIG. 4, a transmissive photosensor 51 is installed above the cover 73 via a mounting hole (not shown). Specifically, after the support plate 71, the code wheel 50, the retaining ring 75, the cover 73, and the bearing 74 are sequentially inserted in the shaft portion of the roller member 47, the transmission type photosensor 51 fixed on the substrate 77 is covered. 73. The photosensor 51 is installed on the cover 73 using a nylon rivet 78 as a resin rivet. Specifically, the photosensor 51 integrated with the substrate 77 is set from above the cover 73, and the through hole provided in the cover 73 and the long hole provided in the holding portion of the photosensor 51 are aligned. Then, after adjusting the vertical direction of the photosensor 51, the position of the photosensor 51 on the cover 73 is fixed by the nylon rivet 51. In the first embodiment, since the nylon rivet 51 is used as a fixing member of the photosensor 51, it is possible to reduce a problem that the photosensor 51 is attached obliquely as compared with the case where screws are used.

  In the first embodiment, the transmissive photosensor 51 is installed above the cover 73 in the direction of gravity. That is, the transmissive photosensor 51 is disposed above the code wheel 50. As a result, even if the photosensor 51 comes into contact with the rotating code wheel 50 to generate shavings of any member, the shavings fall downward in the direction of gravity. Inconveniences caused by erroneous detection due to adhesion to the sensor surface of the photosensor 51 are suppressed.

  Here, with reference to FIG. 7, in the first embodiment, the code wheel 50 is fixed at a position away from the press-fitting region M (the region actually involved in press-fitting) in which the support plate 71 is press-fitted. It is installed. Specifically, the shaft portion of the driven roller 47 is a region N between the press-fitting region M and the fixing position of the code wheel 50 with respect to the shaft diameter in the press-fitting region M (the shaft diameter of the shaft portion 47b). The shaft diameter at (is the shaft diameter of the shaft portion 47a) is reduced. In other words, a non-press-fitted region N (a gap between the inner diameter portion of the support plate 71 and the shaft portion 47a) is provided in the vicinity of the center portion of the attachment surface of the code wheel 50.

  With such a configuration, even when chipping powder is generated from the inner diameter portion of the support plate 71 when the support plate 71 is press-fitted into the shaft portion 47b, the fixed surface of the support plate 71 to which the chipping powder adheres the code wheel 50. The problem that the code wheel 50 is deposited and deformed is suppressed. That is, the shaving powder generated when the support plate 71 is press-fitted into the shaft portion 47 b moves to the fixing surface side (the opposite side of the press-fitting direction) of the code wheel 50 as the support plate 71 is press-fitted. Then, the moved cutting powder K is accumulated in the gap of the non-press-fitted region N. As a result, as described above with reference to FIG. 9, the trouble that the shaving powder K accumulates on the fixed surface (sticking surface) of the code wheel 50 and the code wheel 50 is deformed is prevented. FIG. 9 is for comparison with the configuration of the rotary encoder according to the first embodiment, and does not represent the entire configuration of the conventional rotary encoder.

  As described above, the first embodiment is configured such that the code wheel 50 is fixed to the support plate 71 away from the press-fitting region M. Thereby, even when the code wheel 50 is thinned and reduced in diameter, the code wheel 50 that is indirectly fixed to the shaft portion 47b of the driven roller 47 via the support plate 71 is not deformed. The reliability of detection in the rotary encoder is improved.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a cross-sectional view showing a part of the driven roller 47 in the second embodiment, which corresponds to FIG. 7 in the first embodiment. In the second embodiment, the small diameter portion and the large diameter portion are formed in the inner diameter portion of the support plate 71, and the large diameter portion 47b and the small diameter portion 47a are formed in the shaft portion. 1 is different.

  Also in the second embodiment, similarly to the first embodiment, the transfer belt unit 30 is provided with a driven roller 47 having a rotary encoder. Although a part of the illustration is omitted, the rotary encoder according to the second embodiment also has a code wheel 50, a transmissive photosensor, a support plate 71 (support member), a cover, etc., as in the first embodiment. Consists of.

  Furthermore, referring to FIG. 8, also in the second embodiment, the code wheel 50 is fixed at a position away from the press-fitting region M into which the support plate 71 is press-fitted. Specifically, the inner diameter portion of the support plate 71 is formed so that the hole diameter in the region N between the press-fitted region M and the fixing position of the code wheel 50 is larger than the hole diameter in the press-fitted region M. Yes. In other words, the non-press-fitted region N (the gap between the inner diameter portion of the support plate 71 and the shaft portion 47b) is provided in the vicinity of the center portion of the attachment surface of the code wheel 50. Note that the shaft portion in the second embodiment (the shaft portion on the side where the rotary encoder is installed) is composed of two shaft portions 47a and 47b having different shaft diameters.

  With such a configuration, even when chipping powder is generated from the inner diameter portion of the support plate 71 when the support plate 71 is press-fitted into the shaft portion 47b, the fixed surface of the support plate 71 to which the chipping powder adheres the code wheel 50 The problem that the code wheel 50 is deposited and deformed is suppressed. That is, the shaving powder generated when the support plate 71 is press-fitted into the shaft portion 47 b moves to the fixing surface side of the code wheel 50 as the support plate 71 is press-fitted. Then, the moved cutting powder K is accumulated in the gap of the non-press-fitted region N. As a result, the trouble that the shaving powder K accumulates on the fixed surface of the code wheel 50 and the code wheel 50 is deformed is prevented.

  As described above, also in the second embodiment, the code wheel 50 is configured to be fixed to the support plate 71 apart from the press-fitting region M, similarly to the first embodiment. Thereby, even when the code wheel 50 is thinned and reduced in diameter, the code wheel 50 that is indirectly fixed to the shaft portion 47b of the driven roller 47 via the support plate 71 is not deformed. The reliability of detection in the rotary encoder is improved.

  In each of the embodiments described above, the present invention is applied to the transfer belt unit 30 (belt conveyance device) on which the transfer belt 40 as a belt member is mounted. However, the application of the present invention is not limited to this, and a belt conveyance device (intermediate transfer belt unit) using an intermediate transfer belt as a belt member, or a belt conveyance device (photoconductor) using a photosensitive belt as a belt member. Naturally, the present invention can also be applied to a belt unit. In this case, the rotary encoder according to each of the above embodiments is installed on a belt conveying roller (a driving or driven roller member) that is in contact with the intermediate transfer belt or the photosensitive belt. Similar effects can be obtained. The intermediate transfer belt is a toner image carrier for performing the transfer process in two stages of primary transfer and secondary transfer.

  In each of the embodiments described above, a rotary encoder is installed on the driven roller 47 around which the transfer belt 40 is wound in order to stabilize the running performance of the transfer belt 40. On the other hand, in order to directly control the rotation of the roller member, the rotary encoder of each of the above embodiments can be installed on the roller member. For example, the rotation encoder (feedback control) of the photosensitive drum 21 can be performed by integrally installing the rotary encoder of each of the above embodiments on the shaft portion of the photosensitive drum 21. Even in that case, it is possible to obtain the same effects as those of the respective embodiments.

  In each of the above embodiments, the transmissive photosensor 51 is used as the encoder sensor that detects the rotation of the code wheel 50. However, a reflective photosensor can also be used as the encoder sensor. Even in that case, it is possible to obtain the same effects as those of the respective embodiments.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 2 is a cross-sectional view illustrating a belt conveyance device in the image forming apparatus of FIG. 1. It is sectional drawing which shows the roller member in the belt conveying apparatus of FIG. It is a perspective view which shows a part of rotary encoder in the roller member of FIG. It is a wave form diagram which shows the output signal of a rotary encoder. It is the elements on larger scale which expand and show a part of roller member of FIG. It is sectional drawing which shows a part of roller member in Embodiment 2 of this invention. It is sectional drawing which shows a part of roller member different from this invention.

Explanation of symbols

1 image forming apparatus main body (apparatus main body), 2 optical section,
20, 20Y, 20M, 20C, 20BK Process cartridge,
21 photosensitive drum, 22 charging unit, 23 developing unit,
24 transfer roller, 25 cleaning section,
30 transfer belt unit (belt transport device),
40 Transfer belt (belt member),
41 drive motor, 44 drive roller,
47 driven roller (roller member), 47a-47c shaft,
50 code wheel, 51 transmissive photosensor (encoder sensor),
71 Support plate (support member), 71a Nesting part, 72 Double-sided tape,
73 cover, 73a protrusion,
74 bearings, 75 retaining rings, 77 substrates,
78 Nylon rivet (resin rivet),
85 unit side plate, 86 engaging member,
M Press-fit area, N Non-press-fit area.

Claims (20)

A support member that is press-fitted into the shaft portion of the roller member and rotates together with the shaft portion;
A code wheel fixed to the support member and rotated together with the support member;
With
The code wheel is fixed to the support member apart from the press-fitting region where the support member is press-fitted ,
The rotary encoder according to claim 1, wherein the shaft portion is formed so that a shaft diameter in a region between the press-fitted region and the fixed position of the code wheel is smaller than a shaft diameter in the press-fitted region . 2. The support member is formed so that a hole diameter in a region between the press-fitted region and a fixed position of the code wheel is larger than a hole diameter in the press-fitted region. The rotary encoder described in 1. The rotary encoder according to claim 1, wherein the code wheel is fixed to a side opposite to a press-fitting direction of the support member with respect to the shaft portion. The rotary encoder according to any one of claims 1 to 3, wherein the code wheel is attached to one end face of the support member with a double-sided tape. The rotary encoder according to claim 1, wherein the code wheel is made of a flexible material. The said support member is formed so that the area of the surface which fixes the said code wheel may become smaller than the area of the main surface of the said code wheel. Rotary encoder. The rotary encoder according to any one of claims 1 to 6, wherein the support member is in contact with a step provided in the shaft portion to determine an axial press-fitting position. A cover that is rotatably supported on the shaft portion via a bearing inserted into the shaft portion, and covers the code wheel together with the support member;
An encoder sensor installed in the cover to detect rotation of the code wheel;
The rotary encoder according to any one of claims 1 to 7, further comprising: The rotary encoder according to claim 8, wherein the cover includes one bearing and is cantilevered on the shaft portion. 10. The rotary encoder according to claim 8, wherein the cover and the support member are formed such that opposing surfaces thereof are nested. 11. The rotary encoder according to any one of claims 8 to 10, wherein the cover is fixedly supported such that a fixed position of the encoder sensor is above the gravitational direction. The rotary encoder according to any one of claims 8 to 11, wherein the encoder sensor is a transmissive photosensor disposed so as to sandwich a part of the outer periphery of the code wheel. The rotary encoder according to any one of claims 8 to 12, wherein the encoder sensor is installed on the cover using a resin rivet. 14. The cover according to any one of claims 8 to 13, wherein a position of the cover in the axial direction toward the support member is determined by contacting the bearing with a retaining ring installed in the shaft portion. Rotary encoder. The said cover is urged | biased by the side of the said supporting member while the rotation is latched by the engaging member engaged with the said cover, The Claim 1 characterized by the above-mentioned. Rotary encoder. A roller member, wherein the rotary encoder according to any one of claims 1 to 15 is integrally installed on the shaft portion. A belt conveying device comprising: the roller member according to claim 16; and a belt member wound around a part of an outer peripheral surface of the roller member. The belt conveyance device according to claim 17, wherein the belt member is any one of a transfer belt, an intermediate transfer belt, and a photosensitive belt. An image forming apparatus comprising the roller member according to claim 18. An image forming apparatus comprising the belt conveyance device according to claim 17.

Images