JP5441383B2 - Photosensitive drum unit and electrophotographic apparatus - Google Patents

Description

  The present invention relates to a photosensitive drum unit used in an electrophotographic apparatus, and in particular, a photosensitive drum provided with a photosensitive drum, two flanges fitted at both ends of a base of the photosensitive drum, and a stay disposed inside the photosensitive drum. It relates to the drum unit. The present invention also relates to an electrophotographic apparatus having a unit on the photosensitive drum.

An image forming apparatus employing an electrophotographic method such as a copying machine or a laser beam printer, so-called electrophotographic apparatus,
A photoreceptor (electrophotographic photoreceptor);
Charging means for charging the surface of the photoreceptor;
Exposure means for forming an electrostatic latent image on the surface of the charged photoreceptor;
Developing means for developing the electrostatic latent image with a developer to form a developed image on the surface of the photoreceptor;
Transfer means for transferring the developed image to a transfer material;
The image forming apparatus generally includes a fixing unit for fixing the developed image transferred to the transfer material to the transfer material. As the photoreceptor, a drum-shaped photoreceptor (photosensitive drum) having a cylindrical substrate and a photosensitive layer formed on the substrate is generally used.

  In addition, the photosensitive drum is often used as a photosensitive drum unit in which a flange having a shaft portion is fitted at both ends of a base and a stay is disposed inside the photosensitive drum. And used as rotated (see Patent Document 1).

An example of the photosensitive drum unit is shown in FIG.
The photosensitive drum unit 100 mainly includes a photosensitive drum (101 is a base of the photosensitive drum, and a photosensitive layer is not shown), a flange 102 having a shaft portion 105, and a stay 103. In FIG. 1, two flanges 102 are fitted to both ends of the base 101 of the photosensitive drum, and the flanges 102 are fastened to the fastening portions of both ends of the stay 103 in the longitudinal direction of the photosensitive drum using screws 104. By sandwiching the photosensitive drum base 101 between the two flanges 102 in this way, the two flanges 102 are fixed to both ends of the photosensitive drum.

  Here, when the accuracy of the photosensitive drum unit is not good, for example, when the axis of the photosensitive drum is deviated from the rotation center of the photosensitive drum unit, the surface of the photosensitive drum (when the photosensitive drum unit is incorporated in the electrophotographic apparatus and rotated ( (Outer peripheral surface) is shaken during image formation. As a result, the distance between the surface of the photosensitive drum and the developing means cannot be kept constant, image density unevenness occurs during development, and a good image cannot be obtained. Further, when the photosensitive drum axis is displaced from the rotation center of the photosensitive drum unit, unevenness occurs in the peripheral speed of the surface of the photosensitive drum, so that an image shift during transfer (particularly, a transfer position shifts in a full-color image and the color is shifted). Phenomenon), and a good image cannot be obtained.

  Therefore, it is necessary to reduce the total shake value in the photosensitive drum unit. The total runout is the difference between the diameters of two concentric circumscribed cylinders: a cylinder passing through the maximum outer periphery of the photosensitive drum and a cylinder passing through the minimum outer periphery when the photosensitive drum unit is rotated with reference to the shaft center of the shaft. , “JIS-B0021: 1998 18.16.1 Total runout tolerance in the circumferential direction”.

  In order to reduce the total shake of the photosensitive drum unit, it is necessary to reduce the deviation of the axis of the photosensitive drum from the rotation center of the photosensitive drum unit. As one of the methods, conventionally, it has been performed to improve the accuracy when the flanges are fitted to both ends of the base of the photosensitive drum.

For example, a method is known in which inner surface of both ends of the substrate of the photosensitive drum is subjected to inlay processing, and a flange is fitted into the inlay processing portion (106 in FIG. 1) (see Patent Document 2).
JP 2005-189689 A JP 09-297500 A

  Conventionally, the total shake of the photosensitive drum unit has been reduced by the above method.

  However, recent electrophotographic apparatuses have been improved in resolution and full color, and further higher accuracy is required for the photosensitive drum unit. Specifically, even if the photosensitive drum unit is stored in the electrophotographic apparatus in any environment until it is used for image formation, it is required that the total shake is small at the time of image formation. Has been.

  However, as a result of studies by the present inventors, in the above-described conventional technology, the flange is fitted to both ends of the base of the photosensitive drum and is used for image formation from when the flange is fixed to both ends of the photosensitive drum (when assembled and fixed). In the meantime, it has been found that when the photosensitive drum unit experiences a temperature change, the relative position between the axis of the photosensitive drum and the axis of the shaft portion of the flange may shift (change). As a result, the total shake of the photosensitive drum unit, which was small when assembled and fixed, may change (deteriorate) before it is used for image formation.

  In particular, when the thermal expansion coefficient of the photosensitive drum substrate and the thermal expansion coefficient of the stay arranged inside the photosensitive drum are different, the relative position of the photosensitive drum axis and the shaft center of the flange is assembled due to temperature changes. There was a high possibility that the total deflection of the photosensitive drum unit would be worsened due to deviation from the relative position at the time of fixing.

  The present inventors diligently studied the mechanism by which the relative position of the shaft center of the photosensitive drum and the shaft portion of the flange portion is shifted due to a temperature change, and came to consider as follows.

  That is, first, consider a case where the thermal expansion coefficient of the substrate of the photosensitive drum is larger than the thermal expansion coefficient of the stay and the environment is in a low temperature environment.

  2A is a diagram schematically showing the state of the photosensitive drum unit 200 in a normal temperature environment, and FIG. 2B is a diagram schematically showing the state of the photosensitive drum unit 200 in a low temperature environment. Note that the drawing is exaggerated from the actual situation in consideration of the ease of explanation.

  The photosensitive drum is subjected to inlay processing on the inner surface of the end of the base 201. Hereinafter, the surface that contacts the flange 202 at the end of the substrate 201 of the photosensitive drum is referred to as an inlay processed portion end surface 204, and the surface that faces the side surface 207 of the flange is referred to as an inlay processed portion side surface 206. In FIG. 2, the photosensitive layer formed on the substrate 201 is not shown.

  In order to fit the flange 202 into the end portion of the photosensitive drum base 201, a gap (fitting tolerance) is required between the side surface 206 of the inlay processed portion of the photosensitive drum base 201 and the side face 207 of the flange. . On the other hand, the end surface 204 of the inlay portion of the base 201 of the photosensitive drum and the bottom surface 205 of the flange are in contact with each other.

  Under a low temperature environment, the side surface 206 of the inlay portion is contracted inward of the base 201, and the base 201 of the photosensitive drum is contracted in the longitudinal direction of the photosensitive drum larger than the stay 203. Therefore, the force (holding force) that the flange 202 fixes with the base 201 of the photosensitive drum interposed therebetween is weakened. If the thermal shrinkage and thermal expansion of all materials occur uniformly when returning from the low temperature environment to the normal temperature environment, the state should return to the same state as the original normal temperature environment. However, in practice, the thermal contraction and thermal expansion of all the materials do not occur uniformly, and particularly when the force (holding force) at which the flange 202 fixes the base 201 of the photosensitive drum is weakened, It is difficult to return to the same state as the original room temperature environment. For this reason, the relative position between the axis of the photosensitive drum and the axis of the shaft portion of the flange 202 is shifted. That is, the total shake of the photosensitive drum unit is increased.

  Furthermore, when the thermal expansion coefficient of the flange 202 is larger than the thermal expansion coefficient of the base 201 of the photosensitive drum, the gap (the flange can move inside the base) between the side surface 206 of the spigot processed portion and the side face 207 of the flange is low temperature environment. Therefore, there is a higher possibility that the relative position of the shaft center of the photosensitive drum and the shaft center of the flange 202 is shifted.

  Next, consider the case where the thermal expansion coefficient of the stay is larger than the thermal expansion coefficient of the substrate of the photosensitive drum and the environment is in a low temperature environment.

  3A is a diagram schematically showing the state of the photosensitive drum unit 300 in a normal temperature environment, and FIG. 3B is a diagram schematically showing the state of the photosensitive drum unit 300 in a low temperature environment.

  In this case, under the low temperature environment, the side surface 306 of the inlay portion is contracted in the inner direction of the base 301, and the stay 303 is larger than the base 301 of the photosensitive drum in the longitudinal direction of the photosensitive drum. Therefore, the force (holding force) at which the flange 302 fixes the base 301 of the photosensitive drum with the flange 302 therebetween is maintained. Therefore, in this case, it is unlikely that the relative position of the shaft center of the photosensitive drum and the shaft center of the flange 302 is shifted.

  However, when the thermal expansion coefficient of the flange 302 is larger than the thermal expansion coefficient of the photosensitive drum base 301, the gap between the side surface 306 of the inlayed portion and the side surface 307 of the flange becomes large in a low temperature environment, and therefore the photosensitive drum. There is a possibility that the relative position between the shaft center of the shaft and the shaft center of the shaft portion of the flange 302 is shifted. In FIGS. 3A and 3B, the photosensitive layer formed on the substrate 301 is not shown. Reference numeral 304 denotes an end surface of an inlay processed portion, and reference numeral 305 denotes a bottom surface of the flange.

  In the case of a high temperature environment, a detailed description is omitted, but the completely opposite phenomenon occurs.

  The present invention has been made in view of the above problems, and suppresses the relative position between the shaft center of the photosensitive drum and the shaft portion of the flange shaft portion from deviating from the relative position at the time of mounting and fixing due to a temperature change. Another object of the present invention is to provide a photosensitive drum unit in which a change in total shake from the time of assembly fixing to the time of image formation is small.

  Another object of the present invention is to provide an electrophotographic apparatus having such a photosensitive drum unit.

The present invention includes a photosensitive drum having a cylindrical substrate and a photosensitive layer formed on the substrate, two flanges fitted at both ends of the substrate, and a stay disposed inside the photosensitive drum. A photosensitive drum unit,
The flange has a shaft portion, the stay has a fastening portion for fastening the flange to both end surfaces in the longitudinal direction of the photosensitive drum, and the flange is fastened to the fastening portion, thereby the photosensitive drum. In the photosensitive drum unit that is fixed to both ends, and the thermal expansion coefficient of the base is different from the thermal expansion coefficient of the stay,
The thermal expansion coefficient of the flange and the thermal expansion coefficient of the stay are both smaller than the thermal expansion coefficient of the base body, or the thermal expansion coefficient of the flange and the thermal expansion coefficient of the stay are both lower than the thermal expansion coefficient of the base body. big,
In order to prevent the relative position of the shaft center of the photosensitive drum and the shaft center of the flange from deviating from the relative position when assembled and fixed due to temperature change, a displacement suppression member is provided in the gap between the base and the flange. It is a photosensitive drum unit that is inserted.

  The present invention also provides an electrophotographic apparatus having the photosensitive drum unit, a charging unit, a developing unit, an exposure unit, and a transfer unit.

  According to the present invention, the relative position between the shaft center of the photosensitive drum and the shaft center of the flange shaft portion is prevented from deviating from the relative position at the time of assembly fixing due to a temperature change. It is possible to provide a photosensitive drum unit in which a change in total shake is small.

  Further, according to the present invention, an electrophotographic apparatus having such a photosensitive drum unit can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  4A shows a cross-sectional view of one end of the photosensitive drum unit 400 of the present invention, and FIG. 4B shows a top view thereof.

  The cylindrical base 401 of the photosensitive drum is generally formed of a conductive material such as aluminum, aluminum alloy, iron, and stainless steel. In addition to the above, examples of the conductive material include chromium, molybdenum, gold, indium, niobium, tellurium, vanadium, titanium, platinum, palladium, and alloys thereof.

  The photosensitive drum is formed by forming a photosensitive layer (not shown in FIG. 4) on a cylindrical substrate 401. Examples of the photosensitive layer include an inorganic photosensitive layer such as an amorphous silicon deposited film formed by a CVD method or the like, and an organic photosensitive layer formed by applying a coating liquid by combining a charge generation material and a charge transport material. .

  The flange 402 is generally formed of a conductive metal material such as a resin material, a conductive resin material, aluminum, an aluminum alloy, iron, and stainless steel with a ground electrode.

  Further, since the photosensitive drum base 401 is sandwiched between two flanges 402 (only one is shown in FIG. 4), and these flanges 402 are fastened to a fastening portion of the stay 402 using screws 404 or the like, the stay 403 is sufficient. It is necessary to have strength. Therefore, the stay 403 is preferably formed of a material such as aluminum, aluminum alloy, iron, or stainless steel. The shape of the stay 403 is not particularly limited, but since the photosensitive drum unit is a rotating body, it is preferable that it be lightweight and that the center of gravity of the stay 403 is near the rotation center of the photosensitive drum unit.

Regarding the thermal expansion coefficient, in the present invention, it is sufficient that the thermal expansion coefficients of the photosensitive drum base 401 and the stay 403 are different. However, in order to obtain the effects of the present invention more remarkably, the photosensitive drum base 401 and the flange 402 are used. Further, the relationship between the thermal expansion coefficients of the stay 403 is preferably the following (1) or (2).
(1) The thermal expansion coefficient of the flange 402 and the thermal expansion coefficient of the stay 403 are both smaller than the thermal expansion coefficient of the substrate 401 of the photosensitive drum.
(2) The thermal expansion coefficient of the flange 402 and the thermal expansion coefficient of the stay 403 are both larger than the thermal expansion coefficient of the substrate 401 of the photosensitive drum.

  Although described in detail later, in such a combination, the effect of the present invention is more prominent.

  The displacement restraining member 410 inserted in the gap between the side surface 408 of the inlay portion and the side surface 409 of the flange has a small thermal expansion coefficient compared to the base 401, the flange 402, and the stay 403 of the photosensitive drum, and has sufficient hardness. preferable. From the viewpoint that the coefficient of thermal expansion is small and the hardness is excellent, the deviation suppressing member 410 is preferably formed of a cyanoacrylate compound. Alternatively, it is preferably formed of a resin such as a polycarbonate resin, a polyester resin, a urethane resin, or an acrylic resin.

  Next, the photosensitive drum unit will be described in detail.

  The photosensitive drum unit 400 mainly includes a photosensitive drum, a flange 402 having a shaft portion 405, and a stay 403. In FIG. 4, flanges 402 are fitted to both ends of the base 401 of the photosensitive drum, and the flanges 402 are fixed to the fixing portions of the stay 403 with screws 404. Thereby, the flange 402 is fixed to both ends of the photosensitive drum. There is a gap (fitting tolerance) between the side surface 408 of the spigot portion and the side surface 409 of the flange, and the end surface 406 of the spigot portion and the bottom surface 407 of the flange are in contact with each other.

  In such a state, a slip suppression member 410 is inserted in the gap between the side surface 408 of the spigot part and the side surface 409 of the flange. Even if the gap is filled with the displacement suppressing member 410, it is referred to as a “gap” in the present invention.

  In FIG. 4, four shift suppressing members 410 are put in the gap between the side surface 408 of the spigot part and the side surface 409 of the flange, but the same effect can be obtained by putting four or more. It is preferable to provide it at a symmetrical position with respect to the center of the flange 402 (the axis of the shaft portion of the flange 402). Furthermore, as for the shape of the flange 402, it is preferable to have a plurality of tapered grooves 501 for pouring the material for the displacement suppressing member 410 as shown in FIG. In FIG. 5, 402 is a flange, and 405 is a shaft portion of the flange. By having such a taper-shaped groove 501, the work for putting (pouring) the material for the displacement restraining member 410 into the gap between the base of the photosensitive drum (side surface of the inlay portion) and the flange (side surface thereof) is efficiently performed. It becomes possible.

  Further, the shift suppressing member may be formed in a ring shape as shown in FIG. 8 and disposed around the entire circumference of the flange (the entire gap between the base of the photosensitive drum and the flange). That is, in FIG. 8, the entire gap between the base of the photosensitive drum and the flange is filled with the shift suppressing member 801. In FIG. 8, 401 is a substrate of the photosensitive drum, 402 is a flange, 404 is a screw, and 405 is a shaft portion of the flange.

  Further, the shaft portion of the flange may be subjected in advance to a process for reducing the total runout of the photosensitive drum unit. As a result, it is possible to reduce the total shake of the photosensitive drum unit when it is assembled and fixed.

  Processing for reducing the total shake of the photosensitive drum unit will be described below.

  FIG. 6 is a schematic view of a processing apparatus that reduces the total shake of the photosensitive drum unit. FIG. 6A is a front view, and FIG. 6B is a side view.

  In the processing apparatus 600 shown in FIG. 6, the photosensitive drum unit 606 is supported by applying three sets of support rollers 603a, 603b, 604a, 604b, 605a, and 605b along the outer peripheral surface 602 of the photosensitive drum 601. The support rollers 603a, 604a, and 605a are arranged to abut one end of the photosensitive drum, and the support rollers 603b, 604b, and 605b are arranged to abut the other end of the photosensitive drum. In FIG. 6A, 603a, 603b and 603c are not shown.

  Each support roller is fixed to the processing apparatus 600 by roller shafts 603c, 604c, and 605c set substantially parallel to the center with respect to the outer peripheral surface of the photosensitive drum, so that the support rollers rotate smoothly around the roller shaft. Is set to 603a and 603b, 604a and 604b, and 605a and 605b rotate with a common axis. Support rollers 603a, 603b, 604a, and 604b at positions lower than the center line of the outer peripheral surface of the photosensitive drum are not driven, but have a function of supporting the photosensitive drum unit 606 with high accuracy. Therefore, roller shafts 603c and 604c having a sufficiently high strength to support the photosensitive drum unit 606 are necessary. As the material of the roller shaft, stainless steel or aluminum is preferable. Further, the shape of the roller shaft is preferably a rod shape or a pipe shape. Further, the roller shaft needs to be received by a bearing such as a high-precision bearing or a sintered metal. Furthermore, it is preferable to use a highly accurate support roller, and the material thereof is, for example, a metal material that is not easily worn such as stainless steel, high carbon low chromium steel, or a resin such as polyester resin, urethane resin, or acrylic resin. Is preferred.

  Among the support rollers, the support rollers 605a and 605b that are in contact with a position higher than the center with respect to the outer peripheral surface of the photosensitive drum are rotationally driven by a driving unit including a motor 607a and power transmission units 607b and 607c, and the photosensitive drum unit 606 is driven. It has a function to rotate. Hereinafter, 605a and 605b are referred to as “driving rollers”. As the driving roller, it is preferable to select a material having a small amount of rotational unevenness and a sufficient frictional resistance for driving the photosensitive drum unit 606 as the surface material. As such a material, rubbers such as natural rubber and butadiene rubber, and resins such as urethane and polyester are preferable.

  The support rollers 603a, 603b, 604a, 604b and the drive rollers 605a, 605b are arranged to rotate the photosensitive drum unit 606 around the center 608. The position where the support roller and the driving roller are brought into contact with the surface (outer peripheral surface) of the photosensitive drum is preferably set to the end portion of the photosensitive drum, avoiding an area related to image formation.

  Further, the support rollers 603a, 603b, 604a, and 604b and the driving rollers 605a and 605b are brought into contact with each other in the vicinity of both ends of the photosensitive drum, thereby reducing the rotation center of the photosensitive drum unit. With the photosensitive drum unit 606 rotating, the processing tools 611a and 611b are applied to the outer peripheral surfaces of the shaft portions 610a and 610b of the flanges 609a and 609b so that the processing can be performed concentrically with the outer peripheral surface 602 of the photosensitive drum 601. Processing tools 611a and 611b are installed. The processing tools 611a and 611b are fixed to the tool bases 612a and 612b, and the tool bases are on the rails 613a and 613b, and can be moved as necessary along the processing surface of the shaft portion.

  Furthermore, in order to prevent the photosensitive drum unit 606 from swinging in a direction parallel to the center 608 (left and right in FIG. 6A), it is preferable to include shake suppression rollers 614a and 614b in contact with the side surfaces of the photosensitive drum 601. Further, it is preferable that the driving rollers 605a and 605b can be released from holding in order to put in and out the photosensitive drum unit 606.

  A method for cutting the shaft portions 610a and 610b of the flanges 609a and 609b using the processing apparatus 600 shown in FIG. 6 will be described.

  The photosensitive drum unit 606 is placed on the support rollers 603a, 603b, 604a, and 604b, and the driving rollers 605a and 605b are pressed to hold the photosensitive drum unit 606. Next, the driving rollers 605 a and 605 b are driven, and the photosensitive drum unit 606 is rotated around the center 608 with the outer peripheral surface 602 of the photosensitive drum 601 as a reference. In this state, the processing tools 611a and 611b are pressed against the outer periphery of the shaft portions 610a and 610b of the flanges 609a and 609b, whereby the surfaces of the shaft portions 610a and 610b of the flanges 609a and 609b are concentric with the outer peripheral surface 602 of the photosensitive drum 601. Can be processed. The tool stands 612a and 612b are on the rails 613a and 613b, and are moved along the processing surface of the shaft portion to process a predetermined portion. At the time of machining, if the machining tool 611a from the right and the machining tool 611b from the left are pressed at the same time and machining is performed while simultaneously scanning, the machining time can be shortened. Further, a suction machine (not shown) may be provided in the processing portion so that the photosensitive drum unit 606 is not damaged by the cutting facet during processing. During machining, the machining tools 611a and 611b are scanned, and after machining is completed over the entire length of the shaft portion, the holding of the drive rollers 605a and 605b to the photosensitive drum unit 606 is released with the machining tools 611a and 611b moved and retracted. To do. Thereafter, the processed photosensitive drum unit 606 is taken out.

  Thus, by cutting the surfaces of the shaft portions 610a and 610b of the flanges 609a and 609b with the outer peripheral surface 602 of the photosensitive drum 601 as a reference, the shaft portions 610a and 610b of the flanges 609a and 609b are rotated on the contrary. When this is done, the total shake of the photosensitive drum unit 606 is reduced.

  Next, the case where the temperature of the photosensitive drum unit 400 changes will be described. Assembly and fixing of the photosensitive drum unit 400 is generally performed at normal temperature (about 15 ° C. to 30 ° C.). In general, an electrophotographic apparatus is provided with a charging unit, a developing unit, an exposure unit, a transfer unit, a fixing unit, and the like. Usually, since the fixing unit is a heat source, the temperature in the electrophotographic apparatus is Usually, it becomes higher than room temperature. Further, depending on the electrophotographic apparatus, a heater (drum heater) may be incorporated inside the photosensitive drum unit 400 to keep the photosensitive drum unit at a high temperature in order to suppress the occurrence of image flow under high humidity. Therefore, the use environment temperature of the photosensitive drum unit 400 is generally 15 ° C. to 50 ° C. Further, during transportation of the electrophotographic apparatus and the photosensitive drum unit, there may be a low temperature environment of approximately −20 ° C. In other words, after the photosensitive drum unit 400 is assembled and fixed at room temperature, the photosensitive drum unit 400 is exposed to a low temperature environment up to about −20 ° C. during transportation or even to a high temperature environment up to about 50 ° C. in the electrophotographic apparatus. It is necessary to suppress the change (deterioration) of the total runout of the drum unit.

  Consider changes in the photosensitive drum unit 400 due to temperature changes as described above with reference to FIGS.

  As an example, as in FIG. 2, first, consider the case where the thermal expansion coefficient of the base 401 of the photosensitive drum is larger than the thermal expansion coefficient of the stay 403 and in a low temperature environment.

  Under the low temperature environment, the side surface 408 of the inlay portion is contracted in the inner side of the base body 401, and the base body 401 of the photosensitive drum is contracted in the drum longitudinal direction larger than the stay 403. For this reason, the force (holding force) for fixing the flange 402 with the base 401 of the photosensitive drum interposed therebetween is weakened, so that there is a high possibility that the relative position between the shaft center of the photosensitive drum and the shaft portion of the flange 402 is shifted.

  However, in the present embodiment, the shift restraining member 410 is provided between the side surface 408 of the spigot processing portion and the side surface 409 of the flange, thereby reducing the room for the flange 402 to move inside the substrate 401 of the photosensitive drum. It becomes possible to do. Therefore, even when the thermal shrinkage and thermal expansion of all materials are not uniform when returning from a low temperature environment to a normal temperature environment, it is possible to return to a state close to the original normal temperature environment. This effect becomes more prominent when the thermal expansion coefficient of the flange 402 is smaller than the thermal expansion coefficient of the substrate 401 of the photosensitive drum.

  Next, as in FIG. 3, a case is considered in which the thermal expansion coefficient of the stay is larger than the thermal expansion coefficient of the photosensitive drum substrate, and the stay is in a low temperature environment.

  Under the low temperature environment, the side surface 408 of the inlay portion is contracted inward of the base 401, and the stay 403 is contracted in the longitudinal direction of the photosensitive drum larger than the base 401 of the photosensitive drum. Therefore, the force (holding force) that the flange 402 fixes with the base 401 of the photosensitive drum interposed therebetween is maintained. Therefore, in this case, it is unlikely that the relative position of the shaft center of the photosensitive drum and the shaft center of the flange 402 is shifted.

  However, if the thermal expansion coefficient of the flange is larger than the thermal expansion coefficient of the photosensitive drum substrate, there is room for the flange to move inside the photosensitive drum substrate. The relative position of the shaft center may shift.

  However, in the present embodiment, the shift restraining member 410 is provided between the side surface 408 of the spigot processing portion and the side surface 409 of the flange, thereby reducing the room for the flange 402 to move inside the substrate 401 of the photosensitive drum. It becomes possible to do. Therefore, even when the thermal shrinkage and thermal expansion of all materials are not uniform when returning from a low temperature environment to a normal temperature environment, it is possible to return to a state close to the original normal temperature environment.

  As described above, according to the present invention, even if the photosensitive drum unit experiences a temperature change from when it is assembled and fixed to when it is used for image formation, the change (deterioration) of the total shake of the photosensitive drum unit is reduced. It becomes possible. Therefore, according to the present invention, it is possible to suppress the deviation between the axis of the photosensitive drum and the axis of the shaft portion of the flange.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. In the following description, the same parts as those shown in the above-described embodiment will be described using the same reference numerals. Examples 2, 3, 6, 7, 10, and 11 are reference examples.

In the following examples , reference examples, and comparative examples, pipes made of aluminum or stainless steel having an outer diameter of 109 mm, an inner diameter of 98 mm, and a length of 390 mm were used as the pipes used as the material of the cylindrical substrate of the photosensitive drum. .

  As the flange, an aluminum or iron flange was used.

  As the stay, a 1 mm thick plate made of aluminum or iron was bent, and threaded grooves were cut at both ends so that the flange could be fixed.

(Examples 1-8)
A photosensitive drum unit 400 having the configuration shown in FIG. 4 was produced (however, in FIG. 4, the photosensitive layer formed on the substrate is not shown).

  In this embodiment, the materials of the substrate 401, the flange 402, the stay 403, and the deviation suppressing member 410 of the photosensitive drum are as shown in Table 1, respectively.

In this embodiment, aluminum having a thermal expansion coefficient of 23 × 10 ⁻⁶ / ° C. is used as aluminum, and SUS304 having a thermal expansion coefficient of 17 × 10 ⁻⁶ / ° C. is used as stainless steel. Used iron with a thermal expansion coefficient of 12 × 10 ⁻⁶ / ° C. Table 1 also shows the magnitude relationship between the thermal expansion coefficients.

  The tube material was set on a lathe for machining at both ends, and the tube material was cut to a length of 388 mm while holding the inside of the tube material. Next, an inlay process having a depth of 13 mm and an inner diameter of 100.05 mm was performed on the inner periphery of the end portion of the pipe material. That is, the level difference between the inner peripheral surface of the pipe and the inner peripheral surface of the spigot is about 1 mm ((100.05 mm−98 mm) /2=1.005 mm≈1 mm).

  The tube material subjected to the above processing was set on a lathe for outer peripheral surface processing, and the outer peripheral surface was cut with reference to the inlay processed surface to make the outer diameter 108 mm.

  On the cylindrical substrate 401 thus obtained, an amorphous silicon deposited film as a photosensitive layer was formed by a CVD method to produce a photosensitive drum.

  On the other hand, for the flange 402, after the shaft portion 405 was previously formed on a flange member by a lathe, the shaft portion 405 was set on a lathe using the machining reference, and the flange was cut so that the outer diameter of the flange was 100 mm. Further, a taper-shaped groove 501 as shown in FIG. 5 was provided by additional machining with an end mill having a diameter of 10 mm. In this embodiment, such tapered grooves 501 are provided at four locations.

  With respect to the photosensitive drum, a flange 402, a stay 403, a screw 404, and a sheet-like drum heater (not shown) for heating inside the base body 401 of the photosensitive drum are placed in a 20 ° C. environment (normal temperature environment). Assembled with. Specifically, the flanges are fixed to both ends of the photosensitive drum by fixing the flanges 402 fitted into the base body 401 to the fixing portions on both ends of the stay 403 in the longitudinal direction of the photosensitive drum using screws 404. went.

  Thereafter, in Examples 1 to 4, a silicone compound (trade name “KE-4895”, manufactured by Shin-Etsu Chemical Co., Ltd.) is used as a material for the displacement suppressing member in the four tapered grooves of the flange 402. 30 mg per groove was poured. Moreover, in Examples 5-8, a cyanoacrylate type compound (product name "432FTW" by Toagosei Co., Ltd. product) is grooved in the four tapered grooves of the flange 402 as a material for the displacement suppressing member. 30 mg was poured into each site. To fully cure each compound, it was left in this state for 3 days.

Thereafter, the processing unit shown in FIG. 6 was used to cut the shaft portion 405 to reduce the total shake of the photosensitive drum unit 400.
In this way, 20 photosensitive drum units 400 were produced.
The obtained photosensitive drum unit 400 was evaluated by “total deflection”.

The evaluation of “total deflection” will be described with reference to FIG.
The shaft portions 405 at both ends of the photosensitive drum unit 400 are received by two V blocks 701, and dial gauges 702 and 703 are applied to the outer peripheral surface at a position 10 mm from the end of the photosensitive drum. Then, the maximum value and the minimum value of the indicated values of the dial gauges 702 and 703 when the photosensitive drum unit 400 was rotated once were measured, and the larger difference was defined as the total shake. The measurement was performed under the following conditions.
Measurement 1: After assembling and fixing, 20 units were measured under an environment of 20 ° C. (normal temperature environment).
Measurement 2: 10 photosensitive drum units after measurement 1 were cooled at −20 ° C. (low temperature) for 4 hours, and then returned to a 20 ° C. environment (normal temperature environment).
Measurement 3: Ten photosensitive drum units after measurement 1 were heated to 50 ° C. (high temperature) with a drum heater, heated for 4 hours, and then returned to a 20 ° C. environment (normal temperature environment).

  The evaluation of “total runout” was first performed for the total runout of measurement 1, and the average value of the 20 photosensitive drum units 400 produced was calculated. Next, the total shake of measurement 2 and measurement 3 was performed, and the average value of the 10 photosensitive drum units 400 produced was calculated. Evaluation of the total runout in measurement 2 and measurement 3 was relative evaluation when the evaluation result of measurement 1 was 100. That is, the closer the evaluation result of measurement 2 and measurement 3 is to 100, the smaller the change (deterioration) of the total shake due to the temperature change.

Each evaluation result was ranked according to the following criteria.
AAA ... 90 or more and 100 or less AA ... 80 or more and less than 90 A ... 70 or more and less than 80 B ... 60 or more and less than 70 C ... 50 or more and less than 60 D ... 40 or more and less than 50 E -Less than 40 The results are shown in Table 1.

Moreover, about the evaluation result obtained by each evaluation of the measurement 2 and the measurement 3 as comprehensive evaluation,
AAA rank +6 points,
AA rank +5 points,
A rank +4 points,
B rank +3 points,
C rank +2 points,
+1 D rank,
E rank was set as 0, and ranking was performed as follows based on the total score.
AA ... 11 points or more A ... 9 points or more and 10 points or less B ... 7 points or more and 8 points or less C ... 5 points or more and 6 points or less D ... 3 The results are also shown in Table 1. It is considered that the effect of the present invention is obtained at rank C or higher.

(Comparative Examples 1-4)
A photosensitive drum unit 100 shown in FIG. 1 was produced.

  In this comparative example, the materials of the substrate 101, the flange 102, and the stay 103 of the photosensitive drum are as shown in Table 1, respectively. About the magnitude | size of a thermal expansion coefficient, it is the same as that of Examples 1-8. Table 1 also shows the magnitude relationship between the thermal expansion coefficients.

  The tube material was set on a lathe for both-end processing, and inlay processing was performed in the same manner as in Examples 1-8.

  Thereafter, the outer peripheral surface was cut and the photosensitive layer was formed in the same manner as in Examples 1 to 8, thereby producing a photosensitive drum.

  On the other hand, the flange 102 has an outer diameter of 100 mm. About the shape of a flange, it is the same as that of Examples 1-8.

  With respect to the photosensitive drum, a flange 102, a stay 103 and a screw 104, and a sheet-like drum heater (not shown) for heating inside the substrate of the photosensitive drum are placed in a 20 ° C. environment (normal temperature environment). Assembled.

Thereafter, the shaft portion 105 was cut with the processing apparatus shown in FIG. 6 to reduce the total runout of the photosensitive drum unit 100.
In this way, 20 photosensitive drum units 100 were produced.

  The obtained photosensitive drum unit 100 was evaluated by “total runout” in the same manner as in Examples 1-8. The results are shown in Table 1.

(Examples 9 to 12)
A photosensitive drum unit 400 shown in FIG. 4 was produced.

  In this embodiment, the materials of the base 101, the flange 102, and the stay 103 of the photosensitive drum are as shown in Table 1, respectively. About the magnitude | size of a thermal expansion coefficient, it is the same as that of Examples 1-8. Table 1 also shows the magnitude relationship between the thermal expansion coefficients.

  In this embodiment, a ring-shaped member as shown in FIG. The material was polycarbonate resin as shown in Table 1, and the radial thickness of the deviation suppressing member 801 in FIG. 8 was 5 mm.

  The tube material was set on a lathe for both-end processing, and inlay processing was performed in the same manner as in Examples 1-8.

  Thereafter, the outer peripheral surface was cut and the photosensitive layer was formed in the same manner as in Examples 1 to 8, thereby producing a photosensitive drum.

  On the other hand, a flange 402 having an outer diameter of 90.15 mm was used. The shape of the flange is the same as in Examples 1-8.

A heating sheet-like drum heater (not shown) was mounted inside the substrate 401 of the photosensitive drum. Thereafter, a ring-shaped displacement suppressing member 801 made of polycarbonate resin was attached to the end surface 406 of the inlay processed portion, and then the flange 402 was press-fitted. Further, the flange 402 was fixed to the fastening portion of the stay 403 with a screw 404. These operations were performed at 20 ° C. (room temperature). Thereafter, the shaft unit 405 was cut with the processing apparatus shown in FIG. 6 to reduce the total shake of the photosensitive drum unit 400.
In this way, 20 photosensitive drum units 400 were produced.

  The obtained photosensitive drum unit 400 was evaluated by “total runout” in the same manner as in Examples 1-8. The results are shown in Table 1.

  From Table 1, it can be seen that each example according to the present invention is improved with respect to the comparative example.

  In Examples 1 to 12, with the thermal expansion coefficients of the base of the photosensitive drum and the stay different from each other, a displacement suppression member is inserted in the gap between the base and the flange, so that the temperature change causes the shaft center of the photosensitive drum and the flange to It was possible to prevent the relative position of the shaft center of the shaft portion from deviating from the relative position during assembly fixing. As a result, even when the photosensitive drum unit experienced a temperature change, it was possible to suppress a change (deterioration) in the total shake of the photosensitive drum unit.

  In addition, by comparing Examples 1 to 4 with Examples 5 to 8, the shift suppression member is made of a cyanoacrylate compound (Examples 5 to 8), thereby further changing (deteriorating) the total shake of the photosensitive drum unit. It turns out that it can suppress. Further, by comparing the first to fourth embodiments with the ninth to twelfth embodiments, the change (deterioration) of the total shake of the photosensitive drum unit can be further suppressed by using the resin (Examples 9 to 12) as the shift suppressing member. Recognize. This is presumably because the thermal expansion coefficient of the cyanoacrylate compound or resin is smaller than that of the substrate, flange, and stay of the photosensitive drum, and has sufficient hardness as a displacement suppressing member.

  Further, by comparing the first and fourth embodiments with the second and third embodiments, when the thermal expansion coefficient of the stay and the thermal expansion coefficient of the flange are both smaller than the thermal expansion coefficient of the photosensitive drum substrate, or both are photosensitive drums. When the thermal expansion coefficient of the substrate is larger than that, it can be seen that the change (deterioration) of the total shake of the photosensitive drum unit can be further suppressed. Further, when the fifth and eighth embodiments are compared with the sixth and seventh embodiments, the thermal expansion coefficient of the stay and the thermal expansion coefficient of the flange are both smaller than the thermal expansion coefficient of the photosensitive drum substrate, or both are photosensitive drums. When the thermal expansion coefficient of the substrate is larger than that, it can be seen that the change (deterioration) of the total shake of the photosensitive drum unit can be further suppressed. Further, when the ninth and twelfth examples are compared with the tenth and eleventh examples, both the thermal expansion coefficient of the stay and the thermal expansion coefficient of the flange are smaller than the thermal expansion coefficient of the photosensitive drum substrate, or both are photosensitive drums. When the thermal expansion coefficient of the substrate is larger than that, it can be seen that the change (deterioration) of the total shake of the photosensitive drum unit can be further suppressed.

It is a figure which shows the example of a photosensitive drum unit. (A) is a diagram schematically showing the state of the photosensitive drum unit in a room temperature environment, and (b) is a diagram in a low temperature environment. (A) is a diagram schematically showing the state of the photosensitive drum unit in a room temperature environment, and (b) is a diagram in a low temperature environment. (A) is sectional drawing of the one end part of the photosensitive drum unit of this invention, (b) is the top view. It is a figure which shows an example of the flange which has several taper-shaped groove | channels for pouring the material for deviation | shift control members. (A) is a front view of a processing apparatus for reducing the total shake of the photosensitive drum unit, and (b) is a side view thereof. It is a figure for demonstrating evaluation of a total shake. It is a figure which shows an example of a ring-shaped deviation suppression member.

Explanation of symbols

100, 200, 300, 400, 606 Photosensitive drum unit 101, 201, 301, 401 Photosensitive drum base 601 Photosensitive drum 102, 202, 302, 402, 609a, 609b Flange 103, 203, 303, 403 Stay 104, 404 Screw 105 , 405, 610 a, 610 b Flange shaft portion 106 Inlay processing portion 204, 304, 406 Inlay processing portion end surface 205, 305, 407 Flange bottom surface 206, 306, 408 Inlay processing portion side surface 207, 307, 409 Flange side surface 410, 801 Displacement suppressing member 501 Tapered groove 600 Processing device 602 Photosensitive drum outer peripheral surface 603a, 603b, 604a, 604b Support roller 603c, 604c, 605c Roller shaft 605a, 6 5b drive roller (support roller)
607a Motor 607b, 607c Power transmission means 608 Center 611a, 611b Machining tool 612a, 612b Tool base 613a, 613b Rail 614a, 614b Runout suppression roller 701 V block 702, 703 Dial gauge

Claims (6)

A photosensitive drum unit comprising a photosensitive drum having a cylindrical substrate and a photosensitive layer formed on the substrate, two flanges fitted at both ends of the substrate, and a stay disposed inside the photosensitive drum. There,
The flange has a shaft portion, the stay has a fastening portion for fastening the flange to both end surfaces in the longitudinal direction of the photosensitive drum, and the flange is fastened to the fastening portion, thereby the photosensitive drum. In the photosensitive drum unit that is fixed to both ends, and the thermal expansion coefficient of the base is different from the thermal expansion coefficient of the stay,
The thermal expansion coefficient of the flange and the thermal expansion coefficient of the stay are both smaller than the thermal expansion coefficient of the base body, or the thermal expansion coefficient of the flange and the thermal expansion coefficient of the stay are both lower than the thermal expansion coefficient of the base body. big,
In order to prevent the relative position of the shaft center of the photosensitive drum and the shaft center of the flange from deviating from the relative position when assembled and fixed due to temperature change, a displacement suppression member is provided in the gap between the base and the flange. A photosensitive drum unit that is inserted.   The photosensitive drum unit according to claim 1, wherein the shift suppressing member is formed of a cyanoacrylate compound.   The photosensitive drum unit according to claim 1, wherein the shift suppressing member is made of resin.   The photosensitive drum unit according to claim 1, wherein the flange has a plurality of tapered grooves into which the material for the displacement suppressing member is poured. Photosensitive drum unit according to the shaft portion of the flange, claim 1-4 for machining to reduce the vibration all the photosensitive drum unit is subjected. Photosensitive drum unit according to any one of claims 1 to 5 charging means, developing means, an exposure means, the electrophotographic apparatus having a transfer means and a fixing means.

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