JP3205256U - End member, photosensitive drum unit, and process cartridge - Google Patents

Abstract

Provided is an end member in which an apparatus main body and a photosensitive drum are smoothly attached and detached while sufficiently transmitting a rotational driving force and excellent in productivity. A cylindrical or columnar bearing member that can be engaged and disengaged in a recess of an image forming apparatus main body. The cross-sectional area occupation ratio, which is the degree of the area occupied by the cross-section of the bearing member with respect to the cross-section of the recess, in the cross-section perpendicular to the direction in which the shaft extends in a posture in which the bearing member is engaged is 15% to 75%. The outer peripheral shape of the cross section perpendicular to the direction in which the shaft extends is hexagonal, the radius of the hexagonal circumscribed circle of the bearing member is r1g, and the concave portion is formed in the opening of the concave portion when viewed from the front in the axial direction. A hexagon is formed by the sides surrounded by the triangle formed at the bottom of the recess and the triangle formed at the bottom of the recess, and when the radius of the inscribed circle of the hexagon of the recess is r2h, r1g−r2h> 0 is there. [Selection] Figure 6

Description

  The present invention relates to an end member used in an image forming apparatus such as a laser printer or a copying machine, a photosensitive drum unit including the end member, and a process cartridge.

2. Description of the Related Art Image forming apparatuses such as laser printers and copiers include a process cartridge that is detachable from a main body of the image forming apparatus (hereinafter sometimes referred to as “apparatus main body”).
The process cartridge is a member that forms contents to be represented such as characters and figures in a posture mounted on the apparatus main body and transfers the contents to a recording medium such as paper. For this purpose, the process cartridge is provided with a photosensitive drum on which the content to be transferred is formed, and a charging unit and a developing unit for forming the content to be transferred to the photosensitive drum.

  For process cartridges, the same process cartridge is attached to or detached from the main body for maintenance, or the old process cartridge is detached from the main body to replace it with a new one. Instead, the new process cartridge is attached to the main body. Or put it on. Such a process cartridge can be attached and detached by the user of the image forming apparatus by himself / herself.

In addition, the photosensitive drum included in the process cartridge needs to be rotated during its operation. Therefore, the photosensitive drum is provided with a bearing member so that the driving shaft of the apparatus main body is engaged directly or via another member, and the photosensitive drum is rotated by receiving rotational force from the driving shaft. .
On the other hand, in order to attach and detach the process cartridge to and from the apparatus main body as described above, the engagement (disengagement) between the drive shaft of the apparatus main body and the bearing member provided on the photosensitive drum is re-engaged. It is necessary to fit (install).

In Patent Documents 1 and 2, a drive shaft that moves in the axial direction is provided on the apparatus main body side, and a twisted hole having a polygonal cross section is formed on the drive shaft. There is disclosed a technique including a polygonal columnar protrusion that is inserted into a twisted hole of a drive shaft to transmit a driving force. The protrusion described in Patent Document 1 has a columnar shape that is twisted corresponding to the twisted hole of the drive shaft. On the other hand, the protrusions described in Patent Document 2 are columnar shapes that are not twisted.
Each of the techniques described in Patent Documents 1 and 2 aims to improve the rotational accuracy of the photosensitive drum and reliably transmit the driving force from the apparatus main body to the photosensitive drum.

JP-A-8-328449 Japanese Patent Laid-Open No. 10-153941

However, in the technique including a twisted hole and a twisted columnar protrusion corresponding to the twisted hole as described in Patent Document 1, when a twisted columnar protrusion is produced by injection molding, rotation is given in accordance with the twist of the columnar protrusion. And the mold structure tends to be complex and large. Further, since the mold structure becomes complicated and large, it is difficult to produce a mold capable of simultaneously molding a large number of bearing members having twisted columnar protrusions, such as eight or sixteen.
Further, in the technique described in Patent Document 1, when the process cartridge is detached from the apparatus main body, when the twisted columnar protrusion as the bearing member is detached from the twisted hole of the drive shaft, the rotation opposite to the drive direction is performed. Need to give. Thereby, separation may not be performed smoothly.

  In addition to this, the bearing member provided with the columnar protrusions as described in Patent Documents 1 and 2 can smoothly engage and disengage from the drive shaft of the apparatus body while having sufficient rotation transmission accuracy. That wasn't always enough.

  In view of the above problems, an object of the present invention is to provide an end member that can smoothly attach and detach the apparatus main body and the photosensitive drum while sufficiently transmitting the rotational driving force, and is excellent in productivity. In addition, a photosensitive drum unit including this end member and a process cartridge are provided.

  The present invention will be described below.

According to the first aspect of the present invention, the image forming apparatus main body is provided with a drive shaft having a concave portion that is a twisted hole having a substantially triangular cross-sectional shape, and a photosensitive drum unit that is detachably mounted on the image forming apparatus main body. An end member disposed at the end of the cylinder is provided with a cylindrical or columnar bearing member that can be engaged with and detached from the recess, and the bearing member has an undercut portion on the outer peripheral surface in a direction along the axis. The degree of the area occupied by the cross section of the bearing member relative to the cross section of the recess in the cross section orthogonal to the direction in which the shaft extends at any position where the bearing member is in contact with the recess with the bearing member engaged in the recess The bearing area of the bearing member is 15% or more and 75% or less, and the bearing member has a hexagonal outer peripheral shape in the cross section perpendicular to the direction in which the shaft extends, and the radius of the hexagonal circumscribed circle of the bearing member is r _1g , When the recess is viewed from the front in the axial direction, a hexagon is formed by a side surrounded by the triangle formed at the opening of the recess and the triangle formed at the bottom of the recess, and the hexagon inscribed in the recess When the radius of the circle is r _2h ,
r _1g -r _2h > 0
The problem is solved by the end member.

  The invention described in claim 2 is characterized in that, in the end member according to claim 1, the cross-sectional area occupation ratio is 20% or more and 70% or less.

  According to a third aspect of the present invention, in the end member according to the first or second aspect, the bearing member is in a posture in which the bearing member is engaged in the concave portion, and has a volume occupied by the bearing member with respect to the volume of the concave portion. The degree of volume occupation is 20% or more and 70% or less.

  According to a fourth aspect of the present invention, in the end member according to any one of the first to third aspects, the bearing member is divided into two or more parts.

  The invention according to claim 5 is the end member according to any one of claims 1 to 4, wherein the bearing member is a hexagonal outer peripheral shape of the bearing member and the ridge line of the opening of the recess and the bearing member Chamfering is done at the part other than the part where and contact.

According to a sixth aspect of the present invention, the image forming apparatus main body includes a drive shaft having a recess that is a twisted hole having a substantially triangular cross-sectional shape, and is a photosensitive drum unit that is detachably attached to the image forming apparatus main body. The end member is disposed at the end of the cylinder, and is provided with a cylindrical or columnar bearing member that can be engaged with and detached from the recess, and the bearing member has no undercut portion in the axial direction of the outer peripheral surface thereof. In a posture in which the bearing member is engaged in the recess, the volume occupation ratio, which is the degree of the volume occupied by the bearing member with respect to the volume of the recess, is 20% or more and 70% or less, and the bearing member has a cross section orthogonal to the axial direction. of the outer peripheral shape is hexagonal, the radius of the circumscribed circle of the hexagon of the bearing member and r _{1 g,} and a triangle formed at the opening of the recess when axially viewed from the front of the recess, the bottom of the recess The triangle formed and surrounded by A hexagon is formed by the edge to be turned, and when the radius of the inscribed circle of the hexagon of the recess is r _2h ,
r _1g −r _2h > 0,
The above-mentioned problem is solved by the end member.

  The device described in claim 7 is characterized in that, in the end member according to claim 6, the volume occupancy is 30% or more and 70% or less.

  The invention according to claim 8 is the end member according to claim 6 or 7, wherein the bearing member is divided into two or more parts.

  The invention according to claim 9 is the end member according to any one of claims 6 to 8, wherein the bearing member is a hexagonal outer peripheral shape of the bearing member and the ridge line of the opening of the recess and the bearing member Chamfering is done at the part other than the part where and contact.

  The invention according to claim 10 comprises: a cylindrical photosensitive drum; and an end member according to any one of claims 1 to 9 attached to at least one end of the photosensitive drum. And a photosensitive drum unit.

  The invention described in claim 11 comprises the photosensitive drum unit according to claim 10, a charging roll for charging the photosensitive drum of the photosensitive drum unit, and a developing roll for developing the electrostatic latent image on the photosensitive drum. A process cartridge.

  According to the present invention, the rotational driving force from the apparatus main body is sufficiently transmitted to the photosensitive drum, the apparatus main body and the photosensitive drum unit are smoothly attached and detached, and the productivity of the end member is excellent. It becomes.

1 is a schematic diagram illustrating an image forming apparatus according to one embodiment. FIG. 2A is a perspective view showing one end side of the drive shaft, and FIG. 2B is a front view showing one end side of the drive shaft. It is a figure explaining the shape of a recessed part. It is the figure which showed notionally the structure of the process cartridge. 2 is an external perspective view of a photosensitive drum unit. FIG. It is an external appearance perspective view of an edge part member. FIG. 7A is a front view of the end member, and FIG. 7B is a side view of the end member. It is a figure explaining the shape of a bearing member. 9 (a) is a diagram view illustrating the cross-sectional area A _J, FIG. 9 (b) illustrating the cross-sectional area A _U for determining the cross-sectional area occupying ratio for obtaining the cross-sectional area occupying ratio. It is a perspective view explaining engagement with a bearing member and the recessed part of a drive shaft. It is sectional drawing of the direction along the axis | shaft explaining engagement with a bearing member and the recessed part of a drive shaft. It is sectional drawing orthogonal to the direction where the axis | shaft extends in the site | part which a recessed part and a bearing member contact and transmit rotational force. FIG. 13A is a front view and a perspective view of a modified bearing member 130. FIG. 13B is a front view and a perspective view of a modified bearing member 130 ′. FIG. 14A is a front view and a perspective view of a bearing member 230 according to a modified example. FIG. 14B is a front view and a perspective view of a modified bearing member 230 ′. FIG. 15A is a front view and a perspective view of a modified bearing member 330. FIG. 15B is a front view and a perspective view of a modified bearing member 330 ′.

  The above-mentioned operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these forms.

  FIG. 1 is a diagram illustrating one embodiment, and includes a process cartridge 3 and an image forming apparatus main body 2 (hereinafter sometimes referred to as “apparatus main body 2”) that is used by mounting the process cartridge 3. 1 is a perspective view schematically showing an image forming apparatus 1. FIG. The process cartridge 3 can be attached to and detached from the apparatus main body 2 by moving in the direction indicated by I in FIG.

  The apparatus main body 2 has a drive shaft 51 described below. For other parts, known structures can be used.

  First, the drive shaft 51 provided in the apparatus main body 2 will be described. FIG. 2 shows the end of the drive shaft 51 that is provided in the apparatus main body 2 and applies a rotational driving force to the photosensitive drum unit 10 (see FIG. 5) on the side that engages with the bearing member 30 (see FIG. 6). did. FIG. 2A is a perspective view, and FIG. 2B is a front view. In FIG. 2A and FIG. 2B, a part of the recess 52 is seen through and indicated by a broken line. The opposite end of the drive shaft 51 is directly or indirectly connected to the drive source of the apparatus main body 2. FIG. 3 shows a diagram for explaining the shape of the recess 52. FIG. 3 is a view from the same viewpoint as FIG.

As can be seen from FIGS. 2A and 2B, a recess 52 is provided at the end of the drive shaft 51. The recess 52 is a hole having a substantially equilateral triangular cross section and having a shape that twists about the axis at a predetermined angle as it advances from the end face of the drive shaft 51 in the axial depth direction. Depending on the rotation transmission direction, the twist direction may be clockwise or counterclockwise. In addition, a cylindrical protrusion 53 is erected from the bottom of the recess 52 along the axis from the axial center position of the drive shaft 51.
Therefore, the recess 52 has an opening formed on the end surface of the drive shaft 51 and has a predetermined volume surrounded by the side wall between the opening and the bottom surface of the recess 52. The recess 52 can define a cross-sectional area in each cross section orthogonal to the direction in which the axis of the drive shaft 51 extends (that is, orthogonal to the depth direction of the recess 52).
The projection 53 is not considered in the cross-sectional area and volume at this time.

  As can be seen from FIG. 2B, when the recess 52 is seen through from the front in the axial direction, a triangle (shown by a solid line) formed in the opening of the recess 52 and a bottom of the recess 52 are formed. The triangle (represented by a broken line) appears to overlap two triangles rotated around the axis. The following features are defined from this form. FIG. 3 shows a diagram for explanation.

In FIG. 3, a triangle formed at the opening of the recess 52 is denoted by reference symbol A, and a triangle formed at the bottom of the recess 52 is denoted by reference symbol B. Here, when the recess 52 is viewed from the viewpoint of FIG. 3, a hexagon C having vertices g1 to g6 is formed inside the two triangles A and B (the hexagon C is shown in FIG. 3). (Shown in bold lines.) The circumscribed circle of the hexagon C is C _oh , the inscribed circle of the hexagon C is C _ih , the radius of C _oh is r _1h , and the radius of C _ih is r _2h .
As will be described later, the rotational force can be reliably transmitted when the radius r _2h is related to the predetermined shape of the bearing member 30.

  Here, an example in which the concave portion 52 is a triangle has been described. However, a polygon may be used in which a vertex is slightly cut out while using the triangle as a reference.

  Next, the process cartridge 3 will be described. FIG. 4 schematically shows the structure of the process cartridge 3. As can be seen from FIG. 4, the process cartridge 3 includes a photosensitive drum unit 10 (see FIG. 5), a charging roller 4, a developing roller 5, a regulating member 6, and a cleaning blade 7. With the process cartridge 3 mounted in the apparatus main body 2, the recording medium such as paper moves along the line indicated by IV in FIG. 4 to transfer the image to the recording medium.

As will be described in detail later, the process cartridge 3 is generally attached to and detached from the apparatus main body 2 as follows. Since the photosensitive drum unit 10 provided in the process cartridge 3 receives a rotational driving force from the apparatus main body 2 and rotates, the driving shaft 51 (see FIG. 2) of the apparatus main body 2 and the bearing member of the photosensitive drum unit 10 are at least operated. 30 (see FIG. 6) must be engaged. On the other hand, when the process cartridge 3 is attached to or detached from the apparatus main body 2, the engagement between the drive shaft 51 of the apparatus main body 2 and the bearing member 30 of the photosensitive drum unit 10 needs to be released.
Therefore, the drive shaft 51 of the apparatus main body 2 is configured to be movable in the axial direction, and the drive shaft 51 is detached from the bearing member 30 of the photosensitive drum unit 10 when the process cartridge 3 is attached or detached. On the other hand, after the process cartridge 3 is mounted on the apparatus main body 2, the drive shaft 51 moves and engages with the bearing member 30 of the photosensitive drum unit 10.
As described above, it is preferable that the drive shaft 51 of the apparatus main body 2 and the bearing member 30 of the photosensitive drum unit transmit an appropriate rotational driving force and be smoothly engaged and disengaged.
Each configuration will be described below.

  As described above, the process cartridge 3 includes the charging roller 4, the developing roller 5, the regulating member 6, the cleaning blade 7, and the photosensitive drum unit 10, each of which is as follows.

The charging roller 4 charges the photosensitive drum 11 of the photosensitive drum unit 10 by applying a voltage from the image forming apparatus main body 2. This is performed by the charging roller 4 rotating following the photosensitive drum 11 and contacting the outer peripheral surface of the photosensitive drum 11.
The developing roller 5 is a roller that supplies a developer to the photosensitive drum 11. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing roller 5. The developing roller 5 contains a fixed magnet.
The regulating member 6 is a member that adjusts the amount of the developer adhering to the outer peripheral surface of the developing roller 5 and imparts triboelectric charge to the developer itself.
The cleaning blade 7 is a blade that contacts the outer peripheral surface of the photosensitive drum 11 and removes the developer remaining after the transfer by the tip.

  The photosensitive drum unit 10 includes a photosensitive drum 11 on which characters, graphics, and the like to be transferred to a recording medium are formed. FIG. 5 shows an external perspective view of the photosensitive drum unit 10. As can be seen from FIG. 5, the photosensitive drum unit 10 includes a photosensitive drum 11, a lid material 12, and an end member 20.

The photosensitive drum 11 is a member in which a photosensitive layer is coated on the outer peripheral surface of a cylindrical base. Characters, graphics, and the like to be transferred to a recording medium such as paper are formed on the photosensitive layer.
The base is formed of a conductive material made of aluminum or aluminum alloy in a cylindrical shape. The type of aluminum alloy used for the substrate is not particularly limited, but is a 6000 series, 5000 series, 3000 series aluminum alloy defined by JIS standards (JIS H 4140) which is often used as a substrate of a photosensitive drum. It is preferable that
Further, the photosensitive layer formed on the outer peripheral surface of the substrate is not particularly limited, and a known one can be applied according to the purpose.
The substrate can be manufactured by forming a cylindrical shape by cutting, extruding, drawing, or the like. The photosensitive drum 11 can be manufactured by laminating the photosensitive layer on the outer peripheral surface of the substrate.

  An end member 20 is attached to one end of the photosensitive drum 11 as will be described later, and a lid member 12 is disposed at the other end.

The lid member 12 is a member formed of a resin, and a fitting portion that is inserted inside the cylinder of the photosensitive drum 11 and a bearing portion that is arranged so as to cover one end surface of the photosensitive drum 11 are coaxial. It is combined. The bearing portion has a disk shape that covers the end surface of the photosensitive drum 11 and includes a portion that receives the shaft on the apparatus main body side. In addition, a ground plate made of a conductive material is disposed on the lid member 12, thereby electrically connecting the photosensitive drum 11 and the apparatus main body 2.
Note that although an example of the lid material is shown in this embodiment, the present invention is not limited to this, and it is also possible to apply other forms of the lid material that can be normally taken. For example, a gear for transmitting rotational force may be disposed on the lid material.
Further, the conductive material (ground plate) may be provided on the end member 20 side described later.

  The end member 20 is a member that is attached to the end of the photosensitive drum 11 opposite to the lid member 12, and includes a main body 21 and a bearing member 30. FIG. 6 shows a perspective view of the end member 20. FIG. 7 shows a front view and a side view of the end member 20. 7A is a front view of the end member 20 viewed from the direction indicated by VIIa in FIG. 6, and FIG. 7B is a side view of the end member 20 viewed from the direction indicated by VIIb in FIG. FIG.

  As can be seen from FIGS. 5 to 7, in this embodiment, the end member 20 is configured by integrally forming the main body 21 and the bearing member 30. The end member 20 has a main body 21 mounted on the photosensitive drum 11, and a bearing member 30 provided integrally with the main body 21 is engaged with the drive shaft 51 of the apparatus main body 2 to receive a rotational driving force. The body drum unit 10 is rotated.

  The main body 21 includes a cylindrical body 22, a contact wall 23 that contacts and locks the end surface of the photosensitive drum 11, and a fitting portion 24 that is inserted inside the photosensitive drum 11.

  The cylindrical body 22 is a bottomed cylindrical member having a bottom at one end and a contact wall 23 at the other end. From the bottom of the cylindrical body 22, the bearing member 30 is provided so as to protrude outward.

  The contact wall 23 is a ring-shaped member that is provided on the end of the cylindrical body 22 opposite to the side on which the bearing member 30 is provided, and stands on the outer peripheral surface of the cylindrical body 22. . As can be seen from FIG. 5, the contact wall 23 comes into contact with the end member 20 mounted on the photosensitive drum 11 so that the end surface of the photosensitive drum 11 abuts. As a result, the insertion depth of the end member 20 into the photosensitive drum 11 is restricted.

The fitting portion 24 is a cylindrical portion that protrudes to the opposite side of the contact wall 23 from the side on which the cylindrical body 22 is provided. The fitting portion 24 is inserted inside the photosensitive drum 11 and is fixed to the inner surface of the photosensitive drum 11 with an adhesive. As a result, the end member 20 is fixed to the end of the photosensitive drum 11. Accordingly, the outer diameter of the fitting portion 24 is substantially the same as the inner diameter of the photosensitive drum 11 as long as it can be inserted inside the cylindrical shape of the photosensitive drum 11.
A groove 24 a may be formed on the outer peripheral surface of the fitting portion 24. As a result, the groove 24a is filled with an adhesive, and adhesion between the end member 20 and the photosensitive drum 11 is improved by an anchor effect or the like.

  The bearing member 30 is a member that engages with a recess 52 provided in the drive shaft 51 of the apparatus main body 2 and has a function of transmitting a rotational force from the drive shaft 51 to the end member 20. Further, when the process cartridge 3 is attached to and detached from the apparatus main body 2, the bearing member 30 is configured to be detached from the concave portion 52 of the drive shaft 51. Specifically, the bearing member 30 of the present embodiment has the following shape.

As can be seen from FIGS. 7A and 7B, the bearing member 30 is a cylindrical body provided so as to protrude in the axial direction from the bottom of the cylindrical body 22, and has a cross section orthogonal to the axial direction. The outer peripheral shape is hexagonal and the inner peripheral shape is circular. FIG. 8 is an enlarged view of FIG. 7A and illustrates a shape of the bearing member 30. The bearing member 30 has a shape that becomes a hexagon D from the viewpoint of FIG. Here, the circumscribed circle of the hexagon D is D _og and its radius is r _1g . The radius r _2h of the inscribed circle C _ih of the hexagon C in the recess 52 described with reference to FIG. 3 and the radius r _1g of the circumscribed circle D _og of the hexagon D satisfy the relationship of the following formula (1). .
r _1g -r _2h > 0 (1)

  Since the concave portion 52 of the drive shaft 51 and the bearing member 30 have a shape satisfying the relationship represented by the expression (1), the bearing member 30 and the bearing member can be reliably engaged without idling the rotational driving force from the drive shaft 51. 30 can be transmitted to the end member 20 and the photosensitive drum 11.

Further, the bearing member 30 does not have a so-called twisted shape in the axial direction, and there is no portion that becomes an undercut. Undercut means that the bearing member 30 is viewed in the axial direction from the base side end (end on the main body 21 side) of the bearing member 30 (from the back side opposite to FIG. 7A). The shape is such that the other parts of the bearing member 30 are not visible).
Thereby, when the bearing member 30 (end member 20) is formed, the filling of the material into the mold and the release property are improved, and the productivity is improved. Further, since the slide core and the top rotation mechanism are not required, the configuration of the mold itself can be simplified.

Furthermore, the bearing member 30 has the following form with respect to the recessed part 52 provided in the drive shaft 51 of the apparatus main body 2 with which the bearing member 30 engages. That is, in a posture in which the bearing member 30 is inserted into the recess 52 of the drive shaft 51, the bearing member 30 is in contact with the side surface of the recess 52 and transmits a rotational force, and is orthogonal to the direction in which the shaft extends. in cross section, and is formed so as cross-sectional area occupying ratio a _R is the degree occupied by the cross section of the bearing member 30 relative to the cross section of the recess 52 is 15% or more 75% or less. Preferably they are 20% or more and 70% or less.
Here, the cross-sectional area occupation ratio can be obtained as follows. FIG. 9 shows an explanatory diagram. As will be described later, the bearing member 30 is inserted into the recess 52, whereby the bearing member 30 engages with the drive shaft 51. When the drive shaft 51 rotates, at least a part of the side wall of the recess 52 comes into contact with the outer peripheral portion of the bearing member 30, whereby the rotational force is transmitted to the bearing member 30. Accordingly, the rotational force is transmitted at the contacted portion. Examples of the contact parts will be described later (see FIGS. 11 and 12).
At this time, let _{AJ be} the cross-sectional area of the cross section perpendicular to the direction in which the axis extends of the recess 52 in any of the contacted parts. FIG. 9A shows a cross section of the recess 52. The cross-sectional area _AJ includes all the inside surrounded by the side wall in the cross section without considering the protrusion 53 as shown by hatching in FIG.
On the other hand, the cross-sectional area of the cross section orthogonal to the direction in which the shaft of the bearing member 30 extends at the position corresponding to the cross section of the cross-sectional area A _J among the contacted parts is denoted by A _U. FIG. 9B shows a cross section of the bearing member 30. Sectional area A _U may be considered if there is a hollow portion, as shown by hatching in FIG. 9 (b), do not.
It is possible to obtain the cross-sectional area occupying ratio A _R by the following equation from the defined A _J and A _U as described above.
A _R = (A _U / A _J ) × 100% (2)

If the cross-sectional area occupation ratio _AR is less than 15%, there is a possibility that the bearing member 30 does not engage with the concave portion 52 and runs idle. Moreover, even if it engages temporarily, it cannot endure rotational torque and an engaging part may destroy. In this case, the rotational rigidity of the bearing member 30 is insufficient, and the shaft may be twisted, and the shaft center may be displaced, leading to a decrease in rotational force transmission accuracy.
On the other hand, the cross-sectional area occupying ratio of A _R is the strength of the bearing member 30 itself exceeds 75% improved, the proportion is too large occupancy of the bearing member 30 when engaged in the recess 52, it is smoothly disengaged It may not be possible.

In addition to the cross-sectional area occupying ratio A _R, or separately from the cross-sectional area occupying ratio A _R, the bearing member 30, the volume of the recess 52 to which the bearing member 30 is provided on the drive shaft 51 of the apparatus main body 2 to be engaged against it, it may be formed so that the volume occupancy O _V is the degree of the volume in which the bearing member 30 is inserted is 70% or less than 20%. Preferably they are 30% or more and 70% or less.
Here, the volume occupation ratio O _V can be obtained as follows. That is, if the volume according to the site inserted into the recess 52 of the bearing member 30 V, the volume of the recess 52 is W, it is possible to determine the volume fraction O _V by the following equation (3).
O _V = (V / W) × 100% (3)
Here, in the case of V, when a hollow portion is present in the bearing member 30, it is excluded in consideration of this. On the other hand, for W, the presence of protrusions is not considered as described above.

If the volume occupancy O _V is less than 20%, the bearing member 30 there is a risk that the idling does not engage in the recess 52. Moreover, even if it engages temporarily, it cannot endure rotational torque and an engaging part may destroy. In this case, the bearing member 30 lacks the rigidity in the rotational direction and the shaft may be twisted, and the shaft core may be displaced, leading to a reduction in rotational force transmission accuracy.
On the other hand, the strength of the bearing member 30 itself when the volume occupancy O _V is greater than 80% improved, occupancy is too large, the disengagement may not proceed smoothly when engaged in the recess 52 .

  The inner peripheral shape of the bearing member 30 does not necessarily have a circular cross section, and may be any shape as long as it can engage with the recess 52. In this embodiment, the bearing member 30 is a cylindrical body, but it may be a solid column.

The end member 20 is preferably formed of a crystalline resin. If it is a crystalline resin, when it is injection-molded using a mold, the flow is good, so the molding processability is good, and it is released from the mold by crystallization and solidification without cooling to the glass transition point. be able to. Therefore, productivity can be greatly improved. In addition, the crystalline resin is excellent in heat resistance, solvent resistance, oil resistance, grease resistance, friction wear resistance and slidability, and also in the end member from the viewpoint of rigidity and hardness. It is preferable as a material to be applied.
Examples of the crystalline resin include polyethylene, polypropylene, polyamide, polyacetal, polyethylene terephthalate, polybutylene terephthalate, methylpentene, polyphenylene sulfide, polyether ether ketone, polytetrafluoroethylene, and nylon.
Among these, it is preferable to use a polyacetal resin from the viewpoint of moldability.
Further, from the viewpoint of increasing the strength, glass fiber, carbon fiber or the like may be filled.

  A conductive plate (ground plate) is provided on the end member side including the bearing member 30 and is brought into contact with an electrode provided on the drive shaft 51 side of the apparatus main body 2 so that the photoconductive drum 11 is electrically connected. It is. In that case, the method of forming the bearing member 30 itself with a conductive material or exposing the conductive plate to the inner periphery of the bearing member 30 can be exemplified.

10 to 12 are schematic views showing a mode in which the bearing member 30 provided in the photosensitive drum unit 10 and the concave portion 52 of the drive shaft 51 provided in the apparatus main body 2 are engaged with each other. FIG. 10 is a perspective view schematically showing one scene of the engaged process. FIG. 11 is a diagram schematically showing a cross section in the direction along the axis in a posture in which the recess 52 and the bearing member 30 are engaged. FIG. 12 is a cross-sectional view of a portion indicated by XI in FIG. 11, and shows a portion where the side wall of the recess 52 and the outer peripheral surface of the bearing member 30 are in contact with each other in the posture in which the recess 52 and the bearing member 40 are engaged. It is a sectional view perpendicular to the direction in which the axis extends. Therefore it is possible to calculate the cross-sectional area occupying ratio A _R in this section.

As can be seen from FIG. 10, after the process cartridge 3 is mounted on the apparatus main body 2, the drive shaft 51 moves in the axial direction and the bearing member 30 is inserted inside the recess 52. After the insertion, as shown in FIGS. 11 and 12, at least three of the hexagonal outer peripheral surfaces of the bearing member 30 are partly or entirely part of the end surface side of the recess 52 (in this embodiment, FIG. XI, which is in contact with the ridge line on the opening side of the recess 52) and engages with each other in a posture capable of transmitting the rotational driving force around the axis. This site is the site where contact should seek the cross-sectional area occupying ratio A _R described above in this example.
At this time, the protrusion 53 provided in the recess 52 is inserted into the cylindrical inner space of the bearing member 30.
When the drive shaft 51 and the bearing member 30 are engaged, the drive shaft 51, the bearing member 30, the main body 21, and the photosensitive drum 11 are coaxial.
Further, since the bearing member 30 has no undercut portion, the bearing member 30 operates smoothly when engaged with the recess 52 and when disengaged in the opposite direction.

Next, operations and operations of the image forming apparatus 1 described above will be described.
The process cartridge 3 is attached to the apparatus main body 2 by inserting the process cartridge 3 into the apparatus main body 2 along a predetermined guide as shown in FIG. At this time, the drive shaft 51 of the apparatus main body 2 is in a position retracted from the orbit of movement of the process cartridge 3.
After the process cartridge 3 is placed in a predetermined position of the apparatus main body 2, the drive shaft 51 moves to the process cartridge 3 as shown in FIG. 10 in conjunction with the operation of closing the lid of the apparatus main body 2 or by another operation. As shown in FIGS. 11 and 12, the bearing member 30 is inserted into the recess 52 of the drive shaft 51, and both are engaged coaxially. As a result, the rotational driving force from the apparatus main body 2 is transmitted to the bearing member 30, the end member 20, and the photosensitive drum 11, and can be rotated around the axis in synchronization. Further, the rotational driving force from the apparatus main body 2 is transmitted directly or via other members to other constituent members (for example, the charging roller 4) provided in the process cartridge 3, and these can also rotate.

In this manner, the image forming apparatus is operated in a posture in which the process cartridge 3 is mounted and the photosensitive drum 11 and the like can be rotated. When a desired character or figure is represented on the recording medium, a rotational driving force is applied from the apparatus main body 2, the photosensitive drum unit 10 is rotated, and the photosensitive drum 11 is charged by the charging roller 4.
While the photosensitive drum unit 10 is rotating, laser light corresponding to image information is irradiated to the photosensitive drum 11 using various optical members (not shown), and an electrostatic latent image based on the image information is obtained. This latent image is developed by the developing roller 5.
On the other hand, a recording medium such as paper is set in another part of the apparatus main body 2, conveyed to a transfer position by a delivery roller, a conveyance roller, etc. provided in the apparatus main body 2, and moves along a line IV in FIG. 4. . A transfer unit 1a is disposed at the transfer position. A voltage is applied to the transfer unit 1a as the recording medium passes, and an image is transferred from the photosensitive drum 11 to the recording medium. Thereafter, the image is fixed to the recording medium by applying heat and pressure to the recording medium. Then, the recording medium on which the image is formed is discharged from the apparatus main body 2 by a discharge roll or the like.
In the photosensitive drum 11, the cleaning blade 7 comes into contact with the outer peripheral surface of the photosensitive drum 11 in preparation for the next image, and the developer remaining after the transfer is removed by the tip of the cleaning blade 7. The developer scraped off by the cleaning blade 7 is discharged in a known manner.

There are many opportunities to attach and detach the process cartridge also from the operation and operation of the image forming apparatus, and when the image forming apparatus 1 is operated, the photosensitive drum 11 repeatedly rotates and stops, the load is large, charging, heating, etc. It can be seen that there is a severe condition that there is. According to the present invention, according to the above-described form of the bearing member 30, in addition to the basic function of appropriately transmitting the rotational driving force, the cross-sectional area occupation ratio and / or the volume occupation ratio, and the outer shape (formula ( It is possible to ensure sufficient rotation accuracy according to the relationship 1). Further, since the bearing member 30 is not twisted and there is no undercut portion, the recess 52 and the bearing member 30 can be easily attached and detached.
Further, since the bearing member 30 is not twisted and there is no undercut portion, the material can be filled into the mold and the releasability can be improved, and the productivity can be improved. Further, since the slide core and the top rotation mechanism are not required, the mold configuration can be simplified.

FIG. 13A is a view showing a bearing member 130 included in the modification, in which the upper stage is a front view and the lower stage is a perspective view. FIG. 13B is a view showing a bearing member 130 ′ included in the modification, in which the upper stage is a front view and the lower stage is a perspective view.
The bearing members 130 and 130 ′ are examples in which the bearing member is divided into a plurality of parts. According to this, contact with the unnecessary recessed part of a bearing member can be avoided by removing except the surface which transmits a rotational force. In this case as well, the cross-sectional area occupancy can be obtained at any of the parts that transmit the rotational force (parts that contact the recesses). Further, when the hexagon D shown in FIG. 8 is defined, it can be obtained by supplementing the missing part with a virtual line as shown by the broken line in FIGS. 13 (a) and 13 (b). it can.

FIG. 14A is a view showing a bearing member 230 included in the modification, in which the upper stage is a front view and the lower stage is a perspective view. FIG. 14B is a view showing a bearing member 230 ′ included in the modification, where the upper stage is a front view and the lower stage is a perspective view.
The bearing members 230 and 230 ′ are examples in which chamfering (tapering) is provided at the edge portion of the bearing member. Also by this, it can remove except the surface which transmits rotational force, and can avoid the contact to the unnecessary recessed part of a bearing member. In this case as well, the cross-sectional area occupancy can be obtained at any of the parts that transmit the rotational force (parts that contact the recess). Further, when the hexagon D shown in FIG. 8 is defined, it can be obtained by supplementing the missing part with a virtual line as shown by the broken line in FIGS. 14 (a) and 14 (b). it can.

FIG. 15A is a view showing a bearing member 330 included in the modification, in which the upper stage is a front view and the lower stage is a perspective view. FIG. 15B is a view showing a bearing member 330 ′ included in the modification, in which the upper stage is a front view and the lower stage is a perspective view.
The bearing members 330 and 330 ′ are examples in which a free curved surface according to need is provided on the bearing member. Also by this, it can remove except the surface which transmits rotational force, and can avoid the contact to the unnecessary recessed part of a bearing member. In this case as well, the cross-sectional area occupancy can be obtained at any of the parts that transmit the rotational force (parts that contact the recesses).

Hereinafter, a more specific aspect is illustrated. Consider the influence on the end member when the end member is molded from a polyacetal resin having an outer diameter of 28.5 mm and the form of the bearing member is changed.
Table 1 shows the conditions. Each item described in Table 1 is as follows.

“Bearing member shape” represents the characteristics of the outer peripheral shape of the bearing member, and “twisted triangle” has a triangular cross-sectional shape orthogonal to the direction in which the axis extends, and twists as it moves in the direction along the axis. It means that it is formed like. “Straight hexagon” means a shape in which the outer shape of the cross section perpendicular to the direction in which the axis extends is a hexagon, and the direction along the axis maintains the same cross section without being twisted. “Tapered hexagon” means that the outer shape of the cross section perpendicular to the direction in which the axis extends is hexagonal, and the edge of the outer shape of the tip is chamfered to form a taper shape. The “separated taper hexagon” is the form shown in FIG. Note that neither the “tapered hexagon” or the “separated taper hexagon” is twisted along the axial direction. “Φ7 cylinder” is an example of a cylindrical bearing member having an outer diameter of 7 mm.
“R _1g ” is the radius of the circumscribed circle D _og of the bearing member shown in FIG.
“R _2h ” is the radius of the inscribed circle C _ih of the recess shown in FIG.
“R _1g −r _2h ” represents the left side of the formula (1).
“Expression (1)” indicates whether or not Expression (1) is satisfied, and “○” indicates that it is satisfied, and “X” indicates that it is not satisfied. However, no. 1, no. Since 15 is not a form in which the evaluation can be performed, it is represented by “−”.
The “hole diameter” is the diameter of the hole inside the cylindrical bearing member.
As shown in FIG. 15A, “the C surface of the hole” means chamfering of the edge of the hole on the tip side of the bearing member, and “C0.5” means 0.5 mm of chamfering.
“Height” means the size in the direction along the axis of the bearing member.
“A _J ” is the cross-sectional area of the recess described above.
“A _U ” is a cross-sectional area of the bearing member described above.
The “cross-sectional area occupancy” is obtained by the above equation (2).
“Volume” means the volume (V) of the portion of the bearing member that is inserted into the recess of the drive shaft.
“Volume” means the volume (W) of the recess of the drive shaft. Here, the recess is a hole having a substantially triangular cross section having a shape twisted in the axial direction as shown in FIG.
“Volume occupancy” is obtained by the above equation (3).
“Undercut presence / absence” indicates the presence or absence of the above-described undercut in the direction along the axis of the outer peripheral portion of the bearing member. “◯” indicates that there is no undercut, and “×” indicates that there is an undercut.

For each of the bearing members as described above, a photosensitive drum unit in which an end member provided with the bearing member is bonded to the end of the photosensitive drum is considered. Further, the photosensitive drum unit constitutes a process cartridge, which is mounted on the apparatus main body, the image forming apparatus is operated, and the process cartridge is detached from the apparatus main body. Evaluation is based on the following criteria.
As evaluation (A), mention is made of reliably transmitting the rotational force. If the rotational force can be transmitted, it is 1 point, otherwise it is 0 point.
As evaluation (B), it is mentioned that reverse rotation is not required when attaching and detaching. If reverse rotation is not required, it is 1 point, and if reverse rotation is required, it is 0 point.
As evaluation (C), productivity of the end member is given. 1 point for high productivity and 0 point for low productivity.
As the evaluation (D), the strength as a member is given. 2 points if the strength is sufficient, 1 point when the safety factor is predetermined, and 0 point when the strength is insufficient.
As evaluation (E), smooth attachment / detachment is given. 2 points if the attachment / detachment is sufficiently smooth, 1 point if the minimum smoothness can be secured, and 0 point if the attachment / detachment is not smooth.

About these evaluation (A)-evaluation (E), the score is applied to following Formula (4).
Score = (A) × (E) × [(B) + (C) + (D)] (4)
Then, the score ≧ 7 was “◎”, 5 ≦ score ≦ 6 was “◯”, 3 ≦ score ≦ 4 was “Δ”, and score ≦ 2 was “x”, and the overall evaluation was made. Table 2 shows the results.

No. Reference numeral 1 denotes a bearing member having a twisted shape, which needs to reversely rotate when the bearing member is detached, and cannot be smoothly detached. On the other hand, no. In No. 15, the drive shaft and the bearing member do not mesh with each other in the rotational direction, and the rotational force cannot be transmitted.
As for other examples, when the cross-sectional area occupancy is in the range of 15% or more and 75% or less, the score is 5 or more and the overall evaluation is “◯” or more. Furthermore, if the cross-sectional area occupation ratio is 20% or more, there are two points of evaluation D and evaluation E, respectively, and the evaluation is “◎”.
On the other hand, no. 1, no. When attention is paid to the volume occupancy rate in examples other than 15, the score is 5 points or more in the range of 20% to 70% of the volume occupancy rate, and the overall evaluation is “◯” or more. Furthermore, if the volume occupation ratio is 30% or more, there are two points of evaluation D and evaluation E, respectively, and the evaluation is “◎”.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming apparatus main body 3 Process cartridge 10 Photoconductor drum unit 11 Photoconductor drum 20 End member 30 Bearing member 51 Drive shaft 52 Recessed part

Claims (11)

The image forming apparatus main body is provided with a drive shaft having a concave portion that is a twisted hole having a substantially triangular cross-sectional shape, and is disposed at an end of a photosensitive drum unit that is detachably mounted on the image forming apparatus main body. A member,
A cylindrical or columnar bearing member that can be engaged with and detached from the recess is provided,
The bearing member has no undercut portion on the outer peripheral surface in the direction along the axis,
The section of the bearing member relative to the section of the recess in the section perpendicular to the direction in which the shaft extends at any part where the bearing member contacts the recess in a posture in which the bearing member is engaged in the recess. The cross-sectional area occupancy, which is the degree of area occupied, is 15% to 75%,
The bearing member has a hexagonal outer peripheral shape in a cross section orthogonal to the direction in which the shaft extends,
The radius of the hexagonal circumscribed circle of the bearing member is r _{1 g,} and is surrounded by a triangle formed in the opening of the recess when the recess is viewed from the front in the axial direction and a triangle formed in the bottom of the recess. When the radius of the hexagonal inscribed circle of the recess is r _2h ,
r _1g -r _2h > 0
An end member.   The end member according to claim 1, wherein the cross-sectional area occupation ratio is 20% or more and 70% or less.   The bearing member has a volume occupation ratio of 20% or more and 70% or less, which is a degree of a volume occupied by the bearing member with respect to a volume of the recess in a posture in which the bearing member is engaged in the recess. The end member according to 1 or 2.   The end member according to claim 1, wherein the bearing member is divided into two or more parts.   The said bearing member is chamfered in the hexagonal outer periphery shape of this bearing member except the site | part where the ridgeline of the opening of the said recessed part and the said bearing member contact | connect. End member. The image forming apparatus main body is provided with a drive shaft having a concave portion that is a twisted hole having a substantially triangular cross-sectional shape, and is disposed at an end of a photosensitive drum unit that is detachably mounted on the image forming apparatus main body. A member,
A cylindrical or columnar bearing member that can be engaged with and detached from the recess is provided,
The bearing member does not have an undercut portion in the axial direction of the outer peripheral surface thereof, and the volume occupation ratio is a degree of volume occupied by the bearing member with respect to the volume of the recess in a posture in which the bearing member is engaged in the recess. Is 20% to 70%,
The bearing member has a hexagonal outer peripheral shape in a cross section perpendicular to the axial direction, and a radius of a circumscribed circle of the hexagonal shape of the bearing member is r _1g .
When the concave portion is viewed from the front in the axial direction, a hexagon is formed by a side surrounded by a triangle formed at the opening of the concave portion and a triangle formed at the bottom of the concave portion. When the radius of the tangent circle is r _2h ,
r _1g -r _2h > 0
An end member.   The end member according to claim 6, wherein the volume occupancy is 30% or more and 70% or less.   The end member according to claim 6 or 7, wherein the bearing member is divided into two or more parts.   The said bearing member is chamfered except the site | part where the ridgeline of the opening of the said recessed part and the said bearing member contact among the hexagonal outer periphery shape of this bearing member. End member.   A photosensitive drum unit comprising: a cylindrical photosensitive drum; and an end member according to any one of claims 1 to 9 attached to at least one end of the photosensitive drum. A photosensitive drum unit according to claim 10;
A charging roll for charging the photosensitive drum of the photosensitive drum unit;
And a developing roll for developing an electrostatic latent image on the photosensitive drum.