JP5163420B2 - Imaging unit and image forming apparatus - Google Patents

Description

  The present invention relates to an imaging unit and an image forming apparatus.

  In an electrophotographic image forming apparatus, a unit that includes a photoreceptor on which an electrostatic latent image is formed, a unit that supplies a developer to the photoreceptor and develops a toner image, and a toner image is transferred from the photoreceptor. A unit that holds the intermediate transfer belt in a stretched state, a unit that secondarily transfers the toner image from the intermediate transfer belt to the recording paper, and a unit that heats the recording paper and fixes the toner image are detachably held. In many cases, the image forming apparatus can be replaced or maintained for each unit.

  In such an image forming apparatus, it is necessary to wrap the intermediate transfer belt around the photosensitive member to be in pressure contact so that the toner image is reliably and stably transferred from the photosensitive member to the intermediate transfer belt. For this reason, in the conventional image forming apparatus, as shown in Patent Document 1, rollers for pressing the intermediate transfer belt against the photoreceptor are provided before and after the primary transfer roller. In Patent Document 2 and Patent Document 3, an intermediate transfer belt stretched between two transfer rollers in contact with the inner side of the intermediate transfer belt is brought into contact with the photosensitive member.

  However, in the conventional image forming apparatus, two rollers are required to partially wind the intermediate transfer belt around the photosensitive member, the structure is complicated, and it is difficult to adjust the pressure contact force and the contact range. was there. In particular, in the structure in which the intermediate transfer belt stretched between the two transfer rollers is in contact with the photosensitive member as in the cited documents 2 and 3, the pressure between the photosensitive member and the intermediate transfer belt becomes unstable, The driven rotation of the primary transfer roller inscribed in the intermediate transfer belt also becomes unstable, the load torque and electric resistance applied to the intermediate transfer belt are not stable, color misregistration and image distortion occur, and transfer performance becomes unstable. There was a problem.

In recent years, along with the miniaturization of image forming apparatuses, it has become necessary to ensure the quality of images while reducing the number of parts constituting each unit.
JP 2006-18021 A JP 2000-356885 A JP 2001-350392 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging unit and an image forming apparatus that can stabilize the load torque and electric resistance of an intermediate transfer belt and ensure image quality.

In order to solve the above problem, the imaging unit according to the first means includes:
A photoconductor frame that rotatably holds a photoconductor on which an image is formed;
An intermediate transfer frame that rotatably holds at least two stretching rollers that stretch an intermediate transfer belt to which an image is transferred from the photoreceptor;
A primary transfer roller that is in contact with the inner side of the intermediate transfer belt and is opposed to the photoconductor;
The primary transfer roller is disposed downstream of the intermediate transfer belt in the traveling direction of the intermediate transfer belt and the contact point between the photosensitive member and the intermediate transfer belt upstream of the intermediate transfer belt in the traveling direction, The intermediate transfer belt is pressed against the photoconductor side by a primary transfer roller so that the intermediate transfer belt is partially wound around the photoconductor, and the primary transfer roller is fixed to be non-rotatable.

  In the second means, a fixing portion having a D-shaped cross section is provided at the shaft portion of at least one end of the primary transfer roller, and the fixing portion is engaged with the shaft hole of the photoconductor frame.

  According to the invention comprising the first means, the configuration is simple because only one primary transfer roller is disposed downstream of the contact point between the intermediate transfer belt and the photosensitive member. Compared to a conventional imaging unit having two rollers, the number of parts is reduced. Further, the amount of winding of the intermediate transfer belt can be ensured only by pressing one primary transfer roller against the photoreceptor.

  Since the primary transfer roller is fixed, even if there is eccentricity due to the parts accuracy of the primary transfer roller, there is no effect on the transfer part, the load torque and electrical resistance are stable, and color misregistration and image distortion are eliminated. Transferability is stable. In addition, the diameter of the primary transfer roller can be increased, thereby suppressing the creep phenomenon of the intermediate transfer belt due to the curvature of the roller.

  According to the invention comprising the second means, the fixing structure of the primary transfer roller is simple, no special fixing device is required, and the assemblability is improved without increasing the number of parts.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 1 according to one embodiment of the present invention. The image forming apparatus 1 includes a developing rotary unit 4 that holds a developing unit 3 that supplies cyan, magenta, yellow, and black toner in an annular shape inside a main body 2, and a rotation that can form an electrostatic latent image on the surface. An imaging unit 9 that holds an intermediate transfer belt 8 to which an image formed on the photoreceptor 5 is transferred by a possible photoreceptor 5, a charger 6 that charges the photoreceptor 5, a primary transfer roller 7, and a primary transfer roller 7. An exposure unit 10 that exposes the photosensitive member 5, a two-transfer roller 11, a fixing unit 12, and a paper feed unit 13 are provided.

  The imaging unit 9 includes a photoreceptor frame 14 that holds the photoreceptor 5, the charger 6, and the primary transfer roller 7, an intermediate transfer belt that holds the tension rollers 15 and 16 and the tension roller 17 that stretch the intermediate transfer belt 8. Frame 18. The photoconductor 5 is located outside the intermediate transfer belt 8, the primary transfer roller 7 is in contact with the inside of the intermediate transfer belt 8, and the photoconductor 5 and the primary transfer roller 7 are connected via the intermediate transfer belt 8. It is held so as to face each other. Thus, since the primary transfer roller 7 and the photoconductor 5 are provided on the same photoconductor frame 14, the accuracy of the distance between them can be easily ensured.

  The imaging unit 9 can be attached to and detached from the image forming apparatus 1 by opening the lid 19 of the main body 2, and the stretch roller 15 is attached to the two transfer rollers 11 via the intermediate transfer belt 8 in the mounted state. It comes to be pressed.

  As shown in detail in FIG. 2, the intermediate transfer frame 18 has elongated holes 20 and 21 formed therein. A swing boss 22 that is an end of the rotating shaft of the photoconductor 5 protruding from the photoconductor frame 14 is engaged with the long hole 20, and a rocking boss protruding from the photoconductor frame 14 is engaged with the long hole 21. 23 is engaged. The photoreceptor frame 14 and the intermediate transfer frame 18 can swing with respect to each other within a range in which the swing bosses 22 and 23 can move along the long holes 20 and 21. For this reason, as will be described later, the operability when the imaging unit is attached and detached is improved. Further, if the structure is such that the photoconductor frame 14 and the intermediate transfer frame 8 cannot swing, the number of points for holding (positioning) the unit increases, and a load is intensively applied at the time of attachment / detachment, and the entire unit is distorted, and the intermediate Although there is a problem that the transfer belt 8 is twisted and meandering, in this embodiment, the photoconductor frame 14 and the intermediate transfer frame 8 can swing and can be fixed individually, so that the entire unit can be prevented from being twisted. it can.

  In the swinging range of the photoconductor frame 14 and the intermediate transfer frame 18, the primary transfer roller 7 does not completely enter between the stretching rollers 15 and 16, and the intermediate transfer belt 8 is moved between the stretching rollers 15 and 16. Located so as to be pulled out of the tangent line.

  Further, a rotation stop boss 24 protrudes from the photoconductor frame 14, and the intermediate transfer frame 18 has a rotation stop boss 25 and a positioning boss 26 from which the rotation shafts of the stretching rollers 15 and 16 protrude.

  The primary transfer roller 7 is provided only on one side with respect to the photoreceptor 5, that is, on the downstream side in the traveling direction “a” of the intermediate transfer belt 8. There is no member in contact with the photosensitive member other than the primary transfer roller. Specifically, as shown in FIG. 3, the intermediate transfer belt 8 travels more than the contact S between the intermediate transfer belt 8 and the photoreceptor 5 upstream of the photoreceptor 5 in the travel direction a of the intermediate transfer belt 8. It arrange | positions in the downstream of the direction a. The primary transfer roller 7 presses the intermediate transfer belt 8 toward the photoconductor 5 to partially wind the intermediate transfer belt 8 around the photoconductor 5 to provide a winding portion 8a in a predetermined range. The arc length of the winding portion 8a is preferably in the range of 0.56 to 1.17 mm. In the embodiment, the arc length is about 0.94 mm (angle is about 3.59 °).

In this way, since the configuration is such that only one primary transfer roller 7 is disposed downstream of the contact point S between the intermediate transfer belt 8 and the photoreceptor 5, the configuration is simple, the number of parts is reduced, The device is downsized. Further, the winding amount of the intermediate transfer belt 8 can be ensured only by pressing one primary transfer roller 7 against the photosensitive member 5 side. Because it can ensure the accuracy of the distance to the primary transfer roller 7 or RaMaki mounting portion 8a for applying a transfer current, the transfer region is stabilized, it is possible to maintain good transferability.

  Further, as shown in FIG. 4, the primary transfer roller 7 is provided with a fixing portion 7 b having a D-shaped cross section on a shaft portion 7 a at least one end of the primary transfer roller 7. It is fixed so that it cannot rotate by engaging with the shaft hole 14a and preventing it from coming off with the E-ring 7c. The fixing structure of the primary transfer roller 7 is very simple, no special fixing device is required, and the assemblability is improved without increasing the number of parts.

  Since the primary transfer roller 7 is fixed in a non-rotatable manner, even if there is an eccentricity due to the component accuracy of the primary transfer roller 7, there is no influence on the transfer portion. Further, the load torque and electric resistance of the primary transfer roller 7 are stabilized, color shift and image distortion are eliminated, and the transferability is stabilized. In addition, since the primary transfer portion is formed of a roller having a curvature rather than being formed of sheet metal, the creep phenomenon of the intermediate transfer belt 8 with which the primary transfer roller 7 is pressed can be suppressed. By increasing the diameter of the primary transfer roller 7, it is possible to disperse the load concentrated on the intermediate transfer belt 8 and to prevent deformation.

  Next, the operation at the time of mounting the imaging unit 9 having the above configuration will be described. When the lid 19 is opened and the imaging unit 9 is inserted into the main body 2, the positioning boss 26 is received by a positioning bush 27 formed on the main body 2, and is accurately moved by a pressing lever 28 provided by spring biasing the main body 2. Is positioned. Similarly, a pressing lever 29 provided by spring biasing the main body 2 depresses the swing boss 22 to rotate the imaging unit 9 around the positioning boss 26, but the positioning boss 24 of the photoconductor frame 14. However, it abuts against a regulating portion 30 formed on the main body 2 to regulate the swinging of the photoconductor frame 14.

  Since the intermediate transfer belt 8 stretched around the stretching rollers 15 and 16 of the intermediate transfer frame 18 is tensioned by the tension roller 17, it is disposed inside so as to extend straight between the stretching rollers 15 and 16. The primary transfer roller 7 is pulled in. Since the photoreceptor frame 14 holding the primary transfer roller 7 is positioned by being pressed by the pressing lever 29, the tension of the intermediate transfer belt 8 causes the photoreceptor to move around the intermediate transfer frame 18 around the positioning boss 26. It will be turned toward 5. Then, the rotation stop boss 25 comes into contact with the restricting portion 31 provided on the main body 2 and the position and posture of the intermediate transfer frame 18 are determined.

  As described above, in the present invention, the photosensitive frame 14 and the intermediate transfer frame 18 are swung so as to be attracted to each other by the tension of the intermediate transfer belt 8. 2, the intermediate transfer frame 18 is positioned so as to be pushed into the body 2, so that the intermediate transfer frame 18 can also be positioned by the pulling force acting on the intermediate transfer frame 18.

  Finally, by closing the lid 19, a projecting piece (not shown) provided on the main body 2 presses the lever 32 provided on the main body 2, the lever 32 engages with the positioning boss 25, and the intermediate transfer frame 18 is fixed. Is done.

  In the present invention, since the photoconductor 5 and the primary transfer roller 7 are held on the same photoconductor frame 14, the pressing force between the photoconductor 5 and the primary transfer roller 7 pushes out the intermediate transfer frame 18. Therefore, it is not necessary to hold down the imaging unit 9 with a large force. For this reason, the load concerning the holding levers 28 and 29 provided in the main body 2 is small. Therefore, strength is not required for the main body 2 and the lid 19 of the image forming apparatus 1, and an inexpensive structure can be achieved.

  In the imaging unit 9 of the present invention, the long holes 20 and 21 are formed in the intermediate transfer frame 18, and the swing bosses 22 and 23 that are engaged with the long holes 20 and 21 are protruded from the photoconductor frame 14. Simple connection structure. For this reason, the imaging unit 9 itself can also be provided at low cost.

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. The enlarged view of the imaging unit of FIG. FIG. 3 is a side view showing a positional relationship between a photoconductor and a primary transfer roller. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3 showing a fixing structure of the primary transfer roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Photoconductor 7 Primary transfer roller 7b Fixing part 8 Intermediate transfer belt 8a Winding part 9 Imaging unit 14 Photoreceptor frame 15, 16 Stretching roller 18 Intermediate transfer frame

Claims (3)

A photoconductor frame that rotatably holds a photoconductor on which an image is formed;
An intermediate transfer frame that rotatably holds at least two stretching rollers that stretch an intermediate transfer belt to which an image is transferred from the photoreceptor;
A primary transfer roller that is in contact with the inner side of the intermediate transfer belt and is opposed to the photoconductor;
The primary transfer roller is disposed downstream of the intermediate transfer belt in the traveling direction of the intermediate transfer belt and the contact point between the photosensitive member and the intermediate transfer belt upstream of the intermediate transfer belt in the traveling direction, An imaging unit, wherein the intermediate transfer belt is pressed against the photoconductor side by a primary transfer roller to partially wind the intermediate transfer belt around the photoconductor, and the primary transfer roller is fixed to be non-rotatable.   2. The imaging unit according to claim 1, wherein a fixing portion having a D-shaped cross section is provided on at least one shaft portion of the primary transfer roller, and the fixing portion is engaged with a shaft hole of the photoconductor frame.   An image forming apparatus comprising the imaging unit according to claim 1.

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