JP2005266525A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents nonuniform development density caused by axis displacement between a rotation engagement part on the follower side which is disposed in a developing device and a rotation engagement part on a driving side which transmits rotating force to the rotation engagement part on the follower side, and that restrains banding and hence vibration during drive transmission. <P>SOLUTION: A support shaft 54 is loosely fitted in the rotation center of the rotation engagement part 56 on the follower side so that the rotation engagement part on the follower side can be positionally corrected relative to the developing device 40. The rotation engagement part on the follower side is provided with a positioning fitting part 55 on the follower side, whereas the rotation engagement part 62 on the driving side is provided with a positioning fitting part 65 on the driving side. The positioning fitting parts are fitted together. Thus, the rotation engagement part on the follower side is fixed to make a minute positional correction. On the other hand, driving force transmitted to the rotation engagement part on the follower side is transmitted to the rotating center shaft 50 of the developing roller (developer carrier) 42 via a drive transmission belt 57 wound round a drive pulley 51 and a follower pulley 52. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer. Specifically, a latent image carrier such as a photosensitive member carrying a latent image on the surface and a developer carrier such as a developing roller carrying a developer on the surface, the developer is transferred by the developer carrier. The present invention relates to an image forming apparatus including a developing device that visualizes a latent image on a latent image carrier.

  2. Description of the Related Art Image forming apparatuses such as copying machines, facsimile machines, and printers often use a rotating body such as a drum-shaped photoconductor and a developing roller. In order to transmit the rotational driving force to these rotating bodies, the rotating shaft of the rotating body on the driven side and the rotating shaft on the driving side are connected by a shaft coupling, and the latter rotating shaft is transferred to the former rotating shaft. Those that transmit rotational driving force are known.

  9 and 10 are cross-sectional views showing a rotation engaging portion of a conventional developing device that transmits the rotational driving force as described above.

  The developing device 140 includes a developing roller 142 as a developer carrying member disposed so as to be partially exposed from an opening of a casing 141 that is a developing container, a conveyance screw, a developing doctor, and the like (not shown). Yes. The rotation center shaft 150 of the developing roller 142 extends outward from the inside of the casing 141 from the side surface (right side in the drawing) of the casing 141, and the roller gear 151 is fixed to the rotation center shaft 150 outside the casing 141. . The roller gear 151 is engaged with the engagement gear 152 of the driven side rotation engagement portion 156. The engagement gear 152 is rotatably supported together with a support shaft 154 standing on the side surface of the casing 141, and two claws 153 serving as protrusions are projected from the side surface.

  On the other hand, the driving-side rotation engaging portion 162 provided on the image forming apparatus main body side is provided in a drive output portion 160 that receives driving from a driving motor (not shown). The drive output unit 160 includes a shaft 161 and a driving side rotation engagement portion 162 fixed to the end portion of the shaft 161. The driving side rotation engaging portion 162 has two claws 163 corresponding to the two claws 153 of the engagement gear 152 on the side surface of the engagement plate 164.

  When the developing device 140 is mounted on the image forming apparatus main body side, the driven side rotation engaging portion 156 and the driving side rotation engaging portion 162 are brought into contact with each other as shown in FIG. Then, the driving side rotation engaging portion 162 and the driven side rotation engaging portion 156 are connected. A shaft coupling is constituted by the side part structure of the driven side rotation engaging part and the side part structure of the driving side rotation engaging part 162. With this shaft coupling, the rotational driving force of the drive output unit 160 is connected to the engagement gear 152. Then, the rotational driving force is transmitted to the roller gear 151 meshed with the engagement gear 152, and the developing roller 142 rotates.

In addition to this, a shaft coupling using an Oldham coupling is known as a coupling for coupling two rotating shafts (for example, Patent Document 1). However, since the Oldham joint rubs both the engagement and the slider member with rotation, it is not suitable for transmission of a smooth rotational driving force.
JP-A-6-332285

  The above-described image forming apparatus as shown in FIGS. 9 and 10 also has the following problems.

  The problem is that an axial misalignment occurs between the shaft 161 of the drive output unit 160 and the support shaft 154 of the engagement gear 152 (see FIG. 3). This is because the rotation center shaft 150 provided at one end of the developing roller 142 is inserted into the same side plate 172 of the image forming apparatus main body through which the drive output unit 160 passes. The reason why the rotation center shaft 150 is inserted into the side plate 172 is that the developing roller 142 needs to be positioned with respect to the image forming apparatus main body. There is also a problem that the axial misalignment may occur due to the vibration of the developing device 140.

The axial misalignment slightly changes the rotation speed of the developing roller 142 and causes uneven development density on the image for the following reason.
In the developing process, the toner in the two-component developer on the developing roller 142 is detached from the magnetic carrier and transferred onto the electrostatic latent image on the photoreceptor. At this time, it is preferable that the developing roller 142 rotates at a constant speed while the developing roller 142 maintains a constant gap with the photosensitive member. However, the rotational speed of the developing roller 142 slightly varies due to the axial misalignment, and the toner amount per unit time conveyed to the developing position, which is the position where the photosensitive member and the developing roller 142 face each other, changes. Unevenness occurs.

  In particular, when an image having a relatively large area ratio such as a photograph is printed out, the development density unevenness is conspicuous as compared with an image having a relatively small area ratio such as a text sentence. In a large monochrome image with a high area ratio, a certain development density unevenness occurs in a striped pattern in the sheet passing direction, and the aesthetic appearance is impaired. In a full color image with a large area ratio, uneven development density of each color appears as a hue shift. In the general market, such a large image is sometimes handled in, for example, a design occupation, and the commercial value is remarkably reduced by striped development density unevenness.

  In recent years, in addition to the demand for higher durability of image forming apparatuses, there is a growing demand for higher image quality. In order to achieve high image quality, the gap between the developing roller 142 and the photosensitive member tends to be narrowed. However, as the gap narrows, development density unevenness due to fluctuations in rotational speed has become more prominent, and the axial misalignment cannot be ignored. Further, with the recent reduction in the diameter of the image forming apparatus, the engagement members 152 and 164 themselves of the rotary engagement portions 156 and 162 tend to be reduced in diameter. As the diameters of the engaging members 152 and 164 are reduced, the ratio of axial misalignment to the engaging diameter is increasing.

  In addition, although there is a case where the deviation of the axial center occurs due to the slight vibration at the time of the contact of the gear teeth, the development density unevenness may occur. However, when the spur gear is changed to a helical gear, a significant improvement is observed.

  In view of the above problems, as will be described in detail later, a shaft of a driven-side rotation engaging portion 156 provided in the developing device 140 and a driving-side rotation engaging portion 162 that sends a rotational driving force to the rotation engaging portion 156. As an image forming apparatus that can prevent uneven development density due to misalignment, a driven-side positioning engagement portion is provided on the driven-side rotation engagement portion 156, and the driving-side rotation engagement portion 162 is positioned on the driving side. There has been proposed an image forming apparatus in which a fitting portion is provided and the positioning fitting portions are fitted to each other so that the driven rotation engaging portion is positioned and fixed to perform a fine position correction.

  However, in such an image forming apparatus, when the position of an object having a large axial misalignment is corrected, the pitch between the roller gear 151 and the engagement gear 152 changes greatly, the meshing becomes worse, and the roller gear 151 and the engagement gear 152 Should be in proper meshing as shown in FIG. 12 (A), but it will cause contact with the bottom of the teeth as shown in (B), or it will be in meshing at the tip of the teeth as shown in (C), resulting in poor meshing. This causes vibration (banding).

  An object of the present invention is to prevent development density unevenness caused by axial misalignment between a driven side rotation engaging portion provided in a developing device and a driving side rotation engaging portion that sends a rotational driving force to the rotation engaging portion. The present invention provides an image forming apparatus capable of preventing the occurrence of banding and suppressing vibration during drive transmission.

  In order to achieve the above object, the invention described in claim 1 is characterized in that the rotation center axis of the developer carrier of the developing device is engaged with the positioning portion on the image forming device main body side so that the image forming device main body has the above-mentioned structure. The developer carrying member is rotated by positioning the developing device and connecting the driving side rotation engaging portion provided on the image forming apparatus main body side to the driven side rotation engaging portion provided on the developing device to transmit the driving force. In the image forming apparatus that visualizes the latent image on the latent image carrier by sequentially transferring the developer carried by the developer carrier, the position of the driven rotation engaging portion is corrected in the developing device. The driven side rotation engagement portion is provided with a driven side positioning fitting portion, and the driving side rotation engagement portion is provided with a driving side positioning fitting portion, and the driven side positioning fitting portion is provided. Fit the positioning fitting part on the prime mover side to the Thus, the driven-side rotation engaging portion is fixed to perform subtle position correction, while the driving force transmitted to the driven-side rotation engaging portion is applied to the rotation center axis of the developer carrier via a drive transmission belt. It is characterized by transmitting.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a support shaft is erected on the developer container of the developing device, and the support shaft is loosely fitted to the rotation center of the driven side rotation engagement portion. The driven-side rotation engaging portion is provided in the developing device so as to be able to correct the position.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the driven-side rotation engagement portion is loosely held by the developing container of the developing device, and the driven-side side is held by the developing device. The rotation engaging portion is provided so that the position can be corrected.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the fitting between the driving side positioning fitting portion and the driven side positioning fitting portion is uneven. It is characterized by performing by fitting.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the fitting of the positioning fitting portion on the driving side and the positioning fitting portion on the driven side is performed with a hole. It is characterized by being performed by inserting a shaft into.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, a driven pulley is provided at the driven side rotational engagement portion, and a driven pulley is provided at the rotation center axis of the developer carrier. And transmitting the driving force transmitted to the driven-side rotation engaging portion to the rotation center axis of the developer carrier via a drive transmission belt that is wound around the driving pulley and the driven pulley. Features.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, a groove is formed on the surface of the developer carrying member.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, a development gap that is a surface interval between the latent image carrier and the developer carrier is 0.4 [ mm] or less.

  The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8, wherein the developer is a two-component developer including toner and magnetic particles, and the toner includes an oil-containing toner. Or using a low-melting-point toner, and using the above-mentioned magnetic particles obtained by coating a core material of a magnetic material with a resin coat film, the resin coat film having a resin component obtained by crosslinking a thermoplastic resin and a melamine resin, What contains a charge control agent is used, It is characterized by the above-mentioned.

  According to the first aspect of the present invention, the development density caused by the axial misalignment between the driven-side rotation engaging portion provided in the developing device and the driving-side rotation engaging portion that sends the rotational driving force to the rotation engaging portion. There is an excellent effect that unevenness can be prevented.

The reason why such an effect is obtained will be described below.
The driven-side positioning fitting portion is positioned and fixed by being fitted to the driving-side positioning fitting portion, so that a fine position correction is performed. That is, the driven side rotation engagement portion is not provided with a shaft that is conventionally fixed to the rotation engagement portion and configured to rotate integrally, and before being fitted to the positioning positioning portion on the driving side, development is performed. It is installed so as to be movable in a very small area with respect to the apparatus. And it is comprised so that the driven side rotation engagement part may be positioned by making it fit with the positioning fitting part by the side of a drive. By configuring in this way, subtle axial misalignment that occurs between the driven side and the driving side rotational engagement portion due to problems in parts and design accuracy, etc. is absorbed by the driven side rotational engagement portion. Can do. And the driven side rotation engagement part is always rotated by the rotation center of the driving side rotation engagement part. As a result, the rotational speed of the developer carrying member does not fluctuate due to axial misalignment, and the amount of toner per unit time that is conveyed to the developing position, which is the opposite position between the latent image carrying member and the developer carrying member, varies. And development density unevenness can be prevented.

  Further, the development density caused by the axial misalignment between the driven-side rotation engaging portion for rotating the developer carrier and the driving-side rotation engaging portion that sends the rotational driving force to the rotation engaging portion as described above. As an image forming apparatus capable of preventing unevenness, a driven-side positioning engagement portion is provided on the driven-side rotation engagement portion, and a driving-side positioning engagement portion is provided on the driving-side rotation engagement portion, and the positioning fittings thereof are provided. When an image forming apparatus that performs subtle position correction by positioning and fixing the driven-side rotation engaging portion by fitting the joint portion is used, when an object having a large axial misalignment is corrected, the conventional engagement gear The pitch between the roller gears and the roller gears changed greatly, resulting in poor meshing, and there was vibration around the bottom of the teeth and poor meshing (banding). The fluctuation of the belt In because it is absorbed by suppressing the occurrence of banding due to meshing poor gear, it is possible to suppress vibration during drive transmission.

  According to the second aspect of the present invention, the support shaft is set up on the developing container of the developing device, and the support shaft is loosely fitted to the rotation center of the driven side rotation engagement portion. The driven side rotation engagement portion can be provided so that the position can be corrected.

  According to the third aspect of the present invention, since the driven-side rotation engaging portion is loosely held by the developing container of the developing device, the position of the driven-side rotation engaging portion can be corrected with a simple configuration. Can be provided.

  According to the invention described in claim 4, since the engagement between the positioning fitting portion on the driving side and the positioning fitting portion on the driven side is performed by fitting the unevenness, the positioning fitting on the driven side can be performed with a simple configuration. It is possible to perform delicate position correction by fitting a positioning side fitting part on the driving side to the joint part and positioning and fixing the driven side rotation engaging part.

  According to the fifth aspect of the present invention, the engagement between the driving side positioning fitting portion and the driven side positioning fitting portion is performed by inserting the shaft into the hole. The positioning fitting portion on the driving side is fitted to the positioning fitting portion, and the driven side rotation engaging portion is positioned and fixed to perform delicate position correction.

  According to the sixth aspect of the present invention, the driven pulley is provided on the driven side rotation engaging portion, the driven pulley is provided on the rotation center axis of the developer carrier, and the drive transmission belt is provided on the driven pulley and the driven pulley. The driving force transmitted to the driven side rotation engagement portion via the drive transmission belt is transmitted to the rotation center axis of the developer carrier, so that the variation in the distance between the drive shafts when the axial misalignment is corrected is corrected to the belt. Absorbing by driving, it is possible to suppress the occurrence of banding due to the poor meshing of the conventional gear, and to suppress vibration of drive transmission.

  According to the seventh aspect of the present invention, since there is a groove on the surface of the developer carrying member, the pumping amount of the two-component developer by the developer carrying member is stabilized, and the developing density due to the fluctuation of the rotation speed of the developer carrying member. Not only unevenness but also development density unevenness due to fluctuations in the pumping amount can be suppressed.

  According to the eighth aspect of the present invention, since the development gap, which is the surface interval between the latent image carrier and the developer carrier, is 0.4 [mm] or less, the granularity of the developed toner image is greatly improved. Thus, a high-quality image can be obtained. If the development gap is narrowed in this way, development density unevenness due to fluctuations in the rotation speed of the developer carrier is likely to occur, but in the present invention, the rotation speed fluctuations are suppressed, so image quality deterioration due to development density unevenness occurs. Can be effectively suppressed.

  According to the ninth aspect of the present invention, the developer is a two-component developer composed of toner and magnetic particles, and when an oil-containing toner is used as the toner, the oil naturally oozes out from the toner particles during fixing. Since gloss can be obtained, uneven gloss due to uneven oil application can be avoided. When a low-melting-point toner is used as the toner, fixing can be performed at a temperature lower than that of the conventional toner, so that the fixing unit can be started up early and an energy saving effect can be expected. In addition, as the magnetic particles, a magnetic core material coated with a resin coat film is used, and the resin coat film contains a resin component obtained by crosslinking a thermoplastic resin and a melamine resin, and a charge control agent. The conventional magnetic particles are designed to obtain a long life while gradually cutting the hard coat film, whereas the magnetic particles absorb the impact due to the elasticity of the coat film. Therefore, film scraping can be suppressed. Therefore, the lifetime can be further extended as compared with conventional magnetic particles. As a result, it is possible to expect stabilization of the toner pumping amount, that is, stabilization of quality over a long period of time.

  Embodiments will be described below together with an example in which the present invention is applied to an electrophotographic tandem color laser printer (hereinafter simply referred to as a printer) as an image forming apparatus.

[Overall Configuration] FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer has four sets of process units 1Y for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K) in a printer main body which is an image forming apparatus main body. 1M, 1C, 1K. The symbols with Y, M, C, and K indicate yellow, magenta, cyan, and black (the same applies hereinafter). In addition to the process units 1Y, 1M, 1C, and 1K, an optical writing unit 10, a transfer unit 11, a pair of registration rollers 19, three paper feed cassettes 20, a fixing unit 21 and the like are disposed in the printer body. Yes.

[Optical Writing Unit] The optical writing unit 10 includes four optical writers. Each optical writer includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates a laser beam on the surface of a photoconductor described later based on image data.

[Process Unit] FIG. 2 is a schematic configuration diagram of the process unit 1Y for yellow among the process units 1Y, 1M, 1C, and 1K. Since the other process units 1M, 1C, and 1K have the same configuration, their descriptions are omitted. In FIG. 2, the process unit 1Y includes a drum-shaped photoreceptor 2Y as a latent image carrier, a charger 30Y, a developing device 40Y, a drum cleaning device 48Y, and the like.

  The charger 30Y uniformly charges the drum surface by sliding a charging roller to which an AC voltage is applied against the photoreceptor 2Y. The surface of the photoreceptor 2Y subjected to the charging process is irradiated with the laser beam modulated and deflected by the optical writing unit 10 while being scanned. Then, an electrostatic latent image is formed on the drum surface. The formed electrostatic latent image is developed by the developing device 40Y to become a Y toner image.

  The developing device 40Y has a developing roller 42Y disposed so as to be partially exposed from an opening of a unit case constituting the developing container. Further, it also includes a first transport screw 43Y, a second transport screw 44Y, a developing doctor 45Y, a toner concentration sensor (hereinafter referred to as a T sensor) 46Y, and the like. Then, the developer carried by the developing roller 42Y, which is a developer carrying member, is sequentially transferred to visualize the latent image on the photoreceptor 2Y.

  In the casing, for example, a two-component developer containing a carrier that is magnetic particles and a negatively chargeable Y toner is accommodated. The two-component developer is frictionally charged while being agitated and conveyed by the first conveying screw 43Y and the second conveying screw 44Y, and then carried on the surface of the developing roller 42Y. Then, after the layer thickness is regulated by the developing doctor 45Y, the layer is conveyed to a developing region facing the photoreceptor 2Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 2Y. This adhesion forms a Y toner image on the photoreceptor 2Y. The two-component developer that has consumed Y toner by development is returned to the casing as the developing roller 42Y rotates.

  A partition wall 47Y is provided between the first transport screw 43Y and the second transport screw 44Y. The partition wall 47Y separates the first supply unit that accommodates the developing roller 42Y, the first conveyance screw 43Y, and the like and the second supply unit that accommodates the second conveyance screw 44Y in the unit case. The first transport screw 43Y is driven to rotate by a driving means (not shown), and supplies the two-component developer in the first supply unit to the developing roller 42Y while transporting from the front side to the back side in the drawing. The two-component developer conveyed to the vicinity of the end of the first supply unit by the first conveyance screw 43Y enters the second supply unit through an opening (not shown) provided in the partition wall 47Y. In the second supply unit, the second transport screw 44Y is driven to rotate by a driving unit (not shown), and transports the two-component developer sent from the first supply unit in the direction opposite to that of the first transport screw 43Y. . The two-component developer conveyed to the vicinity of the end of the second supply unit by the second conveyance screw 44Y returns to the first supply unit through the other opening (not shown) provided in the partition wall 47Y. .

  The T sensor 46Y including a magnetic permeability sensor is provided on the bottom wall near the center of the second supply unit, and outputs a voltage having a value corresponding to the magnetic permeability of the two-component developer passing therethrough. Since the magnetic permeability of the two-component developer has a certain degree of correlation with the toner density, the T sensor 66Y outputs a voltage having a value corresponding to the Y toner density. This output voltage value is sent to a control unit (not shown). This control unit includes a RAM, in which Y Vtref, which is a target value of the output voltage from the T sensor 46Y, is stored. In addition, data of M Vtref, C Vtref, and K Vtref, which are target values of output voltage from a T sensor (not shown) mounted in another developing device, is also stored. The Y Vtref is used for driving control of a Y toner conveying device (not shown). Specifically, the control unit drives and controls a Y toner conveying device (not shown) so that the value of the output voltage from the T sensor 46Y approaches the V Vref for Y, and replenishes Y toner in the second supply unit 49Y. Let By this replenishment, the Y toner concentration of the two-component developer in the developing device 40Y is maintained within a predetermined range. Similar toner replenishment control is performed for the developing devices of the other process units 1M, 1C, and 1K.

  The Y toner image formed on the Y photoconductor 2Y is transferred onto a transfer paper conveyed by a paper conveyance belt described later. The surface of the photoreceptor 2Y after the transfer is neutralized by a static eliminator (not shown) after the transfer residual toner is cleaned by the drum cleaning device 48Y. Then, it is uniformly charged by the charger 30Y and prepared for the next image formation. The same applies to the other process units 1M, 1C, and 1K. Each process unit is attachable to and detachable from the printer body, and is replaced when the service life is reached.

[Transfer Unit] In FIG. 1 described above, the transfer unit 11 includes a paper transport belt 12, a drive roller 13, a stretching roller 14, four transfer bias rollers 17Y, 17M, 17C, and 17K. . The paper conveying belt 12 is endlessly moved counterclockwise in the figure by a driving roller 13 rotated by a driving system (not shown) while being tensioned by a driving roller 13 and a stretching roller 14. A transfer bias is applied to each of the four transfer bias rollers 17Y, 17M, 17C, and 17K from a power source (not shown). Then, the paper transport belt 12 is pressed from the back surface toward the photoreceptors 2Y, 2M, 2C, and 2K to form transfer nips. At each transfer nip, a transfer electric field is formed between the photoconductor and the transfer bias roller due to the influence of the transfer bias. The above-described Y toner image formed on the Y photoconductor 2Y is transferred onto the transfer paper P transported on the paper transport belt 12 due to the influence of the transfer electric field and nip pressure. M, C, and K toner images formed on the photoreceptors 2M, 2C, and 2K are sequentially superimposed and transferred onto the Y toner image. By such superposition transfer, a full-color toner image combined with the white color of the paper is formed on the transfer paper P transported on the paper transport belt 12.

[Paper Feed Cassettes] Below the transfer unit 11, three paper feed cassettes 20 for accommodating a plurality of transfer papers P in a stacked manner are arranged in multiple stages, and each cassette is the top transfer paper. A paper feed roller is pressed against P. When the paper feed roller is driven to rotate at a predetermined timing, the uppermost transfer paper P is fed to the paper transport path.

[Registration Roller Pair] The transfer paper P fed from the paper feed cassette 20 to the paper conveyance path is sandwiched between the rollers of the registration roller pair 19. The registration roller pair 19 sends out the transfer paper P sandwiched between the rollers at a timing at which toner images can be superimposed at each transfer nip. As a result, the toner image is superimposed and transferred onto the transfer paper P at each transfer nip. The transfer paper P on which the full color image is formed is sent to the fixing unit 21.

[Fixing Unit] The fixing unit 21 forms a fixing nip by a heating roller 21a having a heat source such as a halogen lamp inside and a pressure roller 21b pressed against the heating roller 21a. The full color image is fixed on the surface of the transfer paper P while being sandwiched in the fixing nip. The transfer paper P that has passed through the fixing unit 21 is discharged out of the apparatus through a pair of paper discharge rollers (not shown).

Next, a characteristic configuration of the printer will be described.
FIG. 3 is a sectional view showing a rotation transmission structure from the printer main body side to the developing device side. The developing device 40 includes a developing roller 42 as a developer carrying member disposed so as to be partially exposed from an opening of a casing 41 that is a developing container, a conveyance screw (not shown), a developing doctor, and the like. From the side surface (right side in the drawing) of the casing 41, the rotation center shaft 50 of the developing roller 42 extends outwardly through the casing 41, and engages with a positioning portion of a side plate 72 provided in the printer main body, thereby engaging the printer. By positioning the process unit 1 within the main body, the developing device 40 is positioned. Outside the casing 41, a driven pulley 51 is fixed and rotated integrally with the rotation center shaft 50 of the developing roller 42. A drive transmission belt 57 is wound around the driven pulley 51 and a drive pulley 52 provided in the driven side rotation engagement portion 56.

  FIG. 4 is a side view showing a state where the drive transmission belt 57 is wound around. (A) shows when the pulley interval between the driven pulley 51 and the driving pulley 52 is in an appropriate state, (B) is too close, and (C) is too far. As can be seen from this figure, the tension rotor 58 is pressed against the outer periphery of the drive transmission belt 57 to eliminate the slack of the drive transmission belt 57.

  FIG. 5 is a schematic perspective view of the driven side rotation engaging portion 56 and a driving side rotation engaging portion 62 described later on the printer main body side. As shown in the figure, two claws 53 as projecting portions are projected from the side surface of the drive pulley 52. Further, the side surface of the drive pulley 52 where the claw 53 is provided is a convex shape for fitting into a concave positioning fitting portion 65 provided on the side surface of the driving side rotation engagement portion 62 on the printer main body side. A positioning fitting portion 55 is provided. The claw 53 is provided in the positioning fitting portion 55. Further, as shown in FIG. 5, an opening for inserting a support shaft 54 standing on a casing 41 which is a developing container of the developing device 40 is provided in the central portion of the driving pulley 52. The diameter of the opening is formed so as to be larger than the diameter of the support shaft 54, and the support shaft 54 is loosely fitted to the rotation center of the driven side rotation engagement portion 56 so that the driven side rotation engagement portion is developed. 56 is provided so that position correction is possible. The support shaft 54 is inserted into the opening without being fixed, and holds the drive pulley 52. For example, the diameter of the opening of the drive pulley 52 is configured to be 1.0 [mm] to 0.5 [mm] larger than the diameter of the support shaft 54.

  On the other hand, as shown in FIG. 3, a drive side member 67 that receives driving from a drive motor (not shown) is provided on the printer body side. The drive side member 67 has a shaft 68 supported by the side plate 72 and a drive gear 69 fixed thereto. The drive gear 69 is configured to mesh with the drive output gear 66. The drive output gear 66 is fixed to a shaft 61 that is rotatably supported by a side plate 72, and the shaft 61 is rotated by a drive motor via a drive gear 69. A driving side rotation engaging portion 62 is fixed to the end portion of the shaft 61. The driving-side rotation engaging portion 62 has two claws 63 corresponding to the two claws 53 of the drive pulley 52 on the side surface of the engagement plate 64. Moreover, as shown in FIG. 5, the cylindrical positioning fitting part 65 protrudes in the circumference | surroundings on the side surface of the engaging plate 64 of the side in which the nail | claw 63 is provided.

  When the developing device 40 is mounted on the printer main body, as shown in FIGS. 3 and 6, the positioning fitting portion 55 of the driving pulley 52 on the developing device 40 side and the driving side rotation engaging portion 62 provided on the printer main body side are arranged. The positioning fitting portion 65 is fitted. At the same time, the two claws 53 and the two claws 63 are hooked to connect the driving side rotation engaging portion 62 provided on the printer main body side to the driven side rotation engaging portion 56 provided on the developing device 40. A shaft coupling is configured by the side structure of the drive pulley 52 and the side structure of the engagement plate 64. By this shaft coupling, the rotational driving force on the printer body side is connected to the driving pulley 52. Then, the driving force transmitted to the driven side rotation engaging portion 56 is transmitted to the rotation center shaft 50 of the developing roller 42 via the driving transmission belt 57, and the developing roller 42 is rotated.

  The positioning fitting portion 55 is positioned and fixed by fitting the concave and convex portions by fitting the positioning fitting portion 55 to the positioning fitting portion 65 of the driving side rotation engaging portion 62, and the driven side drive transmission portion 56 is delicate with respect to the developing device 40. The position is corrected. That is, the driving pulley 52 is not provided with a shaft that is conventionally fixed to the engaging gear and configured to rotate integrally, and before the driving pulley 52 is fitted to the driving-side rotation engaging portion 62 on the printer body side, the developing is performed. The device 40 is installed so as to be movable in a very small area. Then, the drive pulley 52 is positioned by being engaged with the driving side rotation engaging portion 62.

  With this configuration, a subtle axial misalignment that occurs between the driven side rotation engaging portion 56 and the driving side rotation engaging portion 62 due to problems in accuracy of parts and design, etc., can be prevented. It can be absorbed at the joint 56. The driving pulley 52 on the developing device 40 side is always rotated by the rotation center of the driving side rotation engaging portion 62. As a result, fluctuations in the rotational speed of the developing roller 42 due to axial misalignment do not occur, and fluctuations in the amount of toner per unit time conveyed to the developing position, which is the position where the photosensitive member 2 and the developing roller 42 face each other, are eliminated. Uneven development density can be prevented.

  In each process unit 1, the development gap, which is the surface distance between the photoreceptor 2 and the developing roller 42, is preferably 0.4 [mm] or less. As a result, the granularity of the developed toner image can be greatly improved and a high-quality image can be obtained as compared with a case where the development gap is wider than this. When the development gap is narrowed in this way, development density unevenness due to fluctuations in the rotation speed of the developing roller 42 is likely to occur. However, since this printer suppresses the rotation speed fluctuation, image quality deterioration due to the occurrence of development density unevenness is reduced. It can be effectively suppressed.

  Further, it is desirable to stabilize the pumping amount of the two-component developer by carving a groove such as a V groove on the surface of the developing roller 42 or roughening it by sandblasting. By doing so, not only development density unevenness due to fluctuations in the rotation speed of the developing roller 42 but also development density unevenness due to fluctuations in the pumping amount can be suppressed. In general, a developing roller that has been subjected to groove processing such as a V-groove is more preferable than a developing roller that has been sandblasted because it can be stably conveyed with no wear even when used for a long period of time.

  Further, as a carrier as a magnetic particle, a resin component film having a resin coat film on a magnetic core material, and the resin coat film is a resin component obtained by crosslinking a thermoplastic resin such as acrylic and a melamine resin, a charge control agent It is advisable to use those containing. The conventional carrier is configured to obtain a long life while gradually scraping a hard coat film, whereas this carrier absorbs an impact and suppresses the film scraping because the coat film has elasticity. Therefore, the lifetime can be further extended as compared with the conventional carrier. Accordingly, it is possible to expect stabilization of the toner pumping amount, that is, stabilization of quality over a long period of time. In the present embodiment, a carrier having a small particle diameter of 20 [μm] or more and 60 [μm] or less is used as the carrier. The magnetic carrier has a particle size of 60 [μm] or less, and it is possible to prevent grain marks and halftone images from being rough due to the magnetic carrier, that is, deterioration of graininess, improving dot reproducibility and increasing image quality. Is possible. In addition, the magnetic carrier has a particle size of 20 [μm] or more so that the fluidity and stress on the developer are not deteriorated too much.

  As for the toner, it is desirable to use an oil-containing toner containing an oil component. This is due to the following reason. That is, since a glossy image cannot be obtained with a fixing method using an oilless polymerized toner, it is necessary to apply oil to the fixing roller in order to achieve glossiness. If it does so, it will become easy to generate | occur | produce uneven glossiness in an image by the oil application unevenness to a fixing roller. On the other hand, if an oil-containing toner is used, gloss can be naturally produced by oil oozing from the toner particles during fixing, so that uneven gloss due to uneven oil application can be avoided. Examples of the oil-containing toner include the following. That is, first, a prepolymer made of a resin, a compound that extends or crosslinks with the prepolymer, and a toner composition are dissolved or dispersed in an organic solvent. The toner is obtained by inducing a crosslinking reaction or an elongation reaction in the medium and removing the solvent from the dispersion.

  As the toner, it is desirable to use a low melting point toner having a melting point of 140 degrees or less. This is because fixing can be performed at a temperature lower than that of conventional toner, so that the fixing unit can be started up early and an energy saving effect can be expected.

[Modification 1] Next, a modification of the positioning structure of the developing roller with respect to the printer main body will be described.

  7 and 8 are schematic configuration diagrams showing a structure for transmitting rotation to the developing device according to a modification. The basic configuration and operation of this rotational engagement portion are the same as those of the above embodiment, and before the positioning fitting portion on the developing device side is fitted to the positioning fitting portion on the printer body side, the developing device side The rotation engaging portion is configured to be movable in a minute region with respect to the developing device. Hereinafter, differences from the above embodiment will be described.

  In the above embodiment, the support shaft 54 fixed to the developing device is inserted into the opening provided in the central portion of the drive pulley 52. However, in the present modification, the support shaft 54 is provided. Absent. Instead, a hole is provided in the center portion of the drive pulley 252 as a positioning fitting portion 255 provided in the driven side rotation engagement portion 256. In this hole, a shaft as a positioning fitting portion 265 provided in a rotation engaging portion 262 on the printer main body side described later is fitted. Further, in the above embodiment, the drive pulley 52 is held by the support shaft 54, but in this modification, a shaft for holding the drive pulley 252 is not provided, and the casing 41 that is a developing container of the developing device 40. Thus, the driven-side rotation engaging portion 256 is loosely held so as to be movable in a minute region, and the driven-side rotation engaging portion 256 is provided so as to be able to correct the position.

  Moreover, in the said embodiment, although the positioning fitting part 65 of the driving | running | working side rotation engaging part 62 was fitted to the positioning fitting part 55 of the driven side, in this modification, the shaft as the positioning fitting part 265 is used. Is fitted into a hole as the positioning fitting portion 255. The shaft that is the positioning fitting portion 265 on the driving side is provided with a taper as shown in FIG. 7 at the tip of the fitting side in order to smoothly fit into the hole that is the positioning fitting portion 255 on the driven side. ing. Furthermore, in the above embodiment, the two claws 63 respectively corresponding to the two claws 53 of the drive pulley 52 are provided on the side surface of the driving side rotation engagement portion 62 on the printer main body side. Instead of the claw 63, a pin 263 that is fixed through the shaft that is the positioning fitting portion 265 is provided.

  When the developing device is attached to the printer main body, as shown in FIG. 8, the driven side positioning fitting portion 255 and the driving side positioning fitting portion 265 are fitted. In addition, when the two claws 253 and the pin 263 are caught, the rotation engagement portion 256 and the rotation engagement portion 262 are connected. The rotation engagement portion 256 and the rotation engagement portion 262 constitute a shaft coupling. With this shaft coupling, the rotational driving force of the driving side rotation engaging portion 262 is connected to the driven side rotation engaging portion 256. Then, the driving force transmitted to the driven side rotation engaging portion 256 is transmitted to the rotation center shaft 50 via a drive transmission belt 57 (not shown), and the developing roller 42 is rotated.

  The drive pulley 252 is configured to be fixed by inserting a shaft serving as the positioning fitting portion 265 into a hole serving as the positioning fitting portion 255 and performing fine position correction. In other words, the drive pulley 252 is not provided with a shaft that is conventionally fixed to the engaging gear and configured to rotate integrally, but before being fitted to the shaft on the printer main body, It is installed so that it can move in a very small area. The drive pulley 252 is positioned by fitting the shaft, and the drive pulley 252 can be rotated without touching the casing 41.

  With such a configuration, a subtle axial misalignment that occurs between the drive pulley 252 and the shaft due to problems in parts and design accuracy can be absorbed by the driven pulley 252 on the driven side. The driving pulley 252 on the developing device side is always rotated by the rotation center of the shaft. As a result, fluctuations in the rotational speed of the developing roller 42 due to axial misalignment do not occur, and fluctuations in the amount of toner per unit time conveyed to the developing position, which is the position where the photosensitive member 2 and the developing roller 42 face each other, are eliminated. Uneven development density can be prevented.

  The printers used in the above-described embodiments and modifications are examples of apparatuses to which the present invention can be applied, and are not limited to these apparatuses. Although an example in which a two-component developer is applied has been described for the developer, it is naturally applicable to a one-component developer.

1 is a schematic configuration diagram of a color laser printer according to the present invention. It is a schematic block diagram of the process unit used with the laser printer. FIG. 3 is a cross-sectional view showing a rotation transmission structure from the printer main body side to the developing device side. FIG. 4 is a side view showing a state where a drive transmission belt used in the developing device is wound, in which (A) shows when the pulley interval is proper, (B) is too close, and (C) is too far. It is a perspective view of the rotation engaging part of the printer main body and each developing device. It is the state figure which connected those mutual rotation engaging parts. It is sectional drawing which shows the other rotation transmission structure from the printer main body side to the image development apparatus side. It is the state figure which connected those mutual rotation engaging parts. It is sectional drawing which shows the rotation transmission structure from the printer main body side to the image development apparatus side in the past. It is a connection state figure of the rotation engagement part. It is the state enlarged view which connected those mutual rotation engaging parts. FIG. 4 is a diagram showing a gear meshing state on the developing device side at that time, in which (A) is in a proper meshing state, (B) is in contact with a tooth bottom, and (C) is in meshing with a tooth tip. Show.

Explanation of symbols

1Y, 1M, 1C, 1K Process unit 2Y, 2M, 2C, 2K Photoconductor (latent image carrier)
40 Developing Device 41 Casing (Developing Container)
42 Developing roller (developer carrier)
50 Developing roller rotation center shaft 51 Driven pulley 52, 252 Drive pulley 54 Support shaft 55, 255 Driven side positioning fitting portion 56, 256 Driven side rotation engagement portion 57 Drive transmission belt 62, 262 Drive side rotation engagement portion 65, 265 Positioning fitting part on the driving side

Claims (9)

The developing device is positioned in the main body of the image forming apparatus by engaging the rotation center axis of the developer carrier of the developing device with the positioning portion on the main body of the image forming apparatus, and the driving side rotation mechanism provided on the main body of the image forming apparatus. The developer carrying member is rotated by connecting the joint portion to a driven side rotation engaging portion provided in the developing device to transmit the driving force, and the developer carried on the developer carrying member is sequentially transferred. In an image forming apparatus that visualizes a latent image on a latent image carrier,
In the developing device, the driven rotation engaging portion is provided so that the position can be corrected, and
The driven side positioning engagement portion is provided on the driven side rotation engagement portion, the driving side positioning engagement portion is provided on the driving side rotation engagement portion, and the driven side positioning engagement portion is provided on the driving side positioning engagement portion. By fitting the positioning fitting portion, the driven rotation engaging portion is fixed and fine position correction is performed.
Transmitting the driving force transmitted to the driven side rotation engaging portion to the rotation center axis of the developer carrier via a drive transmission belt;
An image forming apparatus.   A support shaft is set up on the developer container of the developing device, the support shaft is loosely fitted to the rotation center of the driven side rotation engaging portion, and the driven side rotation engaging portion is provided in the developing device so that the position can be corrected. The image forming apparatus according to claim 1, wherein:   2. The developing device according to claim 1, wherein the developing-side rotation engaging portion is loosely held and held by a developing container of the developing device, and the developing device is provided with the driven-side rotation engaging portion so that the position thereof can be corrected. The image forming apparatus described.   4. The image formation according to claim 1, wherein fitting between the driving side positioning fitting portion and the driven side positioning fitting portion is performed by fitting irregularities together. 5. apparatus.   The fitting of the positioning fitting part on the driving side and the positioning fitting part on the driven side is performed by inserting a shaft into the hole. Image forming apparatus.   A driven pulley is provided in the driven side rotation engaging portion, and a driven pulley is provided on the rotation center axis of the developer carrier, and the driven side rotation is performed via a drive transmission belt that is wound around the driven pulley and the driven pulley. 6. The image forming apparatus according to claim 1, wherein the driving force transmitted to the engaging portion is transmitted to the rotation center axis of the developer carrying member.   The image forming apparatus according to claim 1, further comprising a groove on a surface of the developer carrying member.   8. The image forming apparatus according to claim 1, wherein a development gap which is a surface interval between the latent image carrier and the developer carrier is 0.4 [mm] or less. .   The developer is a two-component developer composed of toner and magnetic particles, and an oil-containing toner or a low melting point toner is used as the toner, and a magnetic material core material is coated with a resin coating film as the magnetic particles. And the resin coating film comprises a resin component obtained by crosslinking a thermoplastic resin and a melamine resin, and a charge control agent. The image forming apparatus described in 1.

Images