JP3368112B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus using a contact charging method in which a charging member is brought into contact with a rotating photosensitive member to perform charging.

[0002]

2. Description of the Related Art Electrophotographic image forming apparatuses such as electrostatic copying machines, optical printers, and facsimiles charge a photosensitive member, which is a member to be charged, with a toner image formed on the surface of the photosensitive member. A device for transferring to a transfer paper in the transfer step is provided, but a device using a corona discharge method by non-contact charging has been widely used so far.

However, in a corona discharge type charging device, for example, a high voltage is applied to a tungsten wire called a corona wire to perform discharge, and air is ionized to generate a large amount of ozone and nitrogen oxides. Are harmful to the human body, have an adverse effect on the environment, and cause ozone and nitrogen oxides to adhere to various parts of the photoconductor, charger, optical system, etc., causing image deterioration. There was a drawback that it was easy to become.

Especially, since ozone is remarkably generated when a negative discharge is performed, in recent years, a lot of organic photoconductors for negative charging have been used as a photoconductor, and an environmental standard for generated gas. It has become a serious problem due to the becoming severer. Therefore, as a charging device that has almost no such drawbacks as described above, a contact charging type charging device has been attracting attention that charges a charging roller, which is a charging member to which a voltage is applied, in a state of being in contact with a photoconductor.

As the contact charging type charging device, for example, as described in Japanese Patent Laid-Open No. 3-48870, a solenoid is used so that the charging roller of the charging means (charging device) is an image carrier. It is configured so that it can be brought into contact with and separated from a certain photoconductor, and while the charging means charges the photoconductor, the charging roller is brought into contact with the photoconductor with a predetermined pressure, and at other times, the charge roller is exposed to light. There is a device which is brought into non-contact with the body or brought into contact with the body at a pressure smaller than the contact pressure with respect to the photoconductor being charged.

Further, as shown in FIG. 20, the charging roller 6
2 is constantly pressed against the photoconductor 60 by the urging force of the spring 61, so that the photoconductor 60 is always driven to rotate, and the cleaning member 63 comes into contact with the charging roller 62 by operating the solenoid 65 at a timing.・ Some can be separated.

Further, for example, in Japanese Laid-Open Patent Publication No. 3-130787, a charging roller supported by a lever so as to be able to come into contact with and separate from a photosensitive drum is set to a separated position in which the charging roller is separated from the photosensitive drum when charging is not performed. Before the switch is turned on, a cleaning member such as a cleaning roller or a cleaning pad is in contact with the charging roller in the separated position, and when the copy key is turned on, the charging roller rotates while slidingly contacting the cleaning member. A charging device in which the surface of a charging roller is cleaned is described. It is noted that, in this charging device, it is desirable that the time for rotating the charging roller at the separated position is equal to or longer than the time required for one rotation in order to clean the entire peripheral surface of the charging roller.

[0008]

However, as shown in FIG.
In the charging device shown in (1), the charging roller 62 is always driven along with the photoconductor 60. Therefore, the surface peripheral speed of the charging roller 62 is constant regardless of whether the charging roller 62 is cleaned by the cleaning member 63 or not. . Therefore, when the charging roller is rotated by receiving the driving force from the photoconductor as described above, the surface peripheral speed of the charging roller is equal to the image forming speed (the process linear velocity corresponding to the surface peripheral speed of the photoconductor). ), There was a case where inconvenience occurred.

For example, in an image forming apparatus having a high process linear velocity, the peripheral velocity of the surface of the charging roller which is in sliding contact with the cleaning member is increased, so that the toner is fixed or the charging roller is thermally affected by the sliding contact. However, there is a problem that the surface of the is susceptible to mechanical damage.

Further, in the case where the charging roller is in a state of being in contact with the surface of the photoconductor, a driving force is obtained by a frictional force from the photoconductor to be driven to rotate (rotate), A belt is stretched between the pulley that rotates integrally and the pulley that is integral with the charging roller.When the charging roller separates from the photoconductor, the belt does not loosen, and the charging roller is driven by the drive transmitted by the belt. If the cleaning member rotates while contacting the cleaning member, inconvenience may occur.

That is, when the charging roller is in contact with the photosensitive member and is rotated together with the belt so that the belt is slackened, the belt does not hinder the rotation of the charging roller. When separated from each other, the charging roller cannot be driven by the frictional force from the photoconductor, and immediately after the separation, the belt is still slack between the pulleys and cannot be driven by the belt, so it stops. It becomes a state. Then, when the charging roller moves to a position where it comes into contact with the cleaning member, the belt reaches a predetermined tension, where the driving force from the belt is transmitted to the pulley on the charging roller side, and the charging roller starts rotating for the first time at that time. Like

Therefore, in this case, the charging roller starts rotating after coming into contact with the cleaning member.
The contact portion of the charging roller with the cleaning member comes into sliding contact with the cleaning member with a static friction force larger than the dynamic friction force, and after rotation, the entire circumference comes into sliding contact with the dynamic friction force. Therefore, a part of the charging roller, which is brought into sliding contact by the static frictional force, exerts a load on the charging roller, which causes local abrasion, which is repeated, and there is a possibility that stable charging cannot be performed.

The present invention has been made in view of the above problems, and prevents the surface of a charging member such as a charging roller from being mechanically damaged or locally abraded so that stable charging can be achieved. The purpose is to be able to.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rotating photoconductor and a photoconductor which is rotated in the opposite direction to the photoconductor while contacting the photoconductor. A charging member for uniformly charging the surface, a cleaning member for cleaning the surface of the charging member, and a means for contacting / separating the charging member with respect to the photoconductor are provided, and when the charging member is separated from the photoconductor. In an image forming apparatus in which the charging member is rotated while being in contact with the cleaning member to perform cleaning, the state in which the charging member is in contact with the photosensitive member is changed to the separated state.
Then, the charging member is rotated and separated from each other.
The speed reducing means is provided to reduce the surface peripheral speed of the electric member with respect to the surface peripheral speed when the charging member rotates while contacting the photosensitive member.

By doing so, even in the case of an image forming apparatus having a high process linear velocity, the surface peripheral velocity when the charging member is separated from the photoconductor is slower than that when the charging member is rotated while being in contact with the photoconductor. Therefore, when the peripheral speed of the surface is high, it is possible to prevent the toner from sticking and mechanical damage to the surface of the charging member, which are likely to be caused by the heat generated by the sliding contact of the charging member with the cleaning member.

Further, it is preferable that the charging member is rotated in a direction opposite to the rotating direction of the photoconductor when it comes into contact with the photoconductor. By doing so, the charging member comes into contact with the photoconductor while rotating, so that the surface of the charging member can be prevented from being locally worn. Further, since the charging member and the photoconductor come into contact with each other with a dynamic frictional force smaller than the static frictional force, damage to the photoconductor surface can be prevented. Furthermore, if the charging member is rotated when coming into contact with the cleaning member, the charging member comes into contact with the cleaning member by a dynamic frictional force, so that the surface of the charging member is less likely to be damaged, and The load for driving the charging member can be smaller than that when the charging member is brought into contact with the cleaning member in a stopped state and then rotated.

Further, it is preferable that the rotating direction when the charging member rotates while contacting the photosensitive member and the rotating direction when the charging member rotates while contacting the cleaning member are the same. By doing so, even when the charging member is rotated while being in contact with the photoconductor, the charging member is separated and brought into contact with the cleaning member, the rotation direction is the same, so that the charging member is rapidly rotated in the opposite direction. A large shock load will not be applied to the drive system and the support portion of the charging member as in the case of hitting. Therefore,
It is possible to prevent the surface of the charging member from being locally worn by the cleaning member due to the influence of the shock.

Further, the deceleration means transmits the rotational force from the rotary drive source for rotationally driving the charging member to the charging member when the charging member is separated from the photoconductor, and the photosensitive member of the charging member. When contacting the body, the rotational force from the rotational drive source is stopped from being transmitted to the charging member via the rotational force transmitting means, and when the charging member is separated from the photoconductor, the rotational force from the rotational drive source is rotated. A one-way clutch for transmitting the force to the charging member via the force transmitting means may be provided.

Then, the one-way clutch prevents the rotational force from the rotary drive source from being transmitted to the charging member through the rotational force transmitting means when the charging member comes into contact with the photosensitive member, so that the charging member is exposed to light. When separated from the body, the rotational force from the rotary drive source is transmitted to the charging member via the rotational force transmitting means, so that the peripheral surface speed of the charging member can be switched instantaneously.

Further, if the photoconductor is used as a rotary drive source for rotationally driving the charging member when the charging member is brought into contact with the photoconductor, the driving of the charging member at the time of image formation is provided with a new rotational force transmitting means. Since the charging member can be rotated by contact drive (rotation) with respect to the photoconductor without the provision of the above, uniform and uniform charging can be performed. Further, the rotational force transmission means may be a gear train in which a plurality of gears meshing with each other are arranged, or a configuration including a plurality of pulleys and a belt stretched between the pulleys.

Furthermore, it is preferable that the charging member is brought into contact with the photosensitive member while being rotated in a direction opposite to the rotating direction of the photosensitive member. By doing so, the charging member comes into contact with the photoconductor with a small dynamic frictional force while rotating, so that it is possible to prevent local wear of the charging member and prevent damage to the surface of the photoconductor.

The rotating photoconductor, the charging member that rotates while being in contact with the photoconductor to uniformly charge the surface thereof, the cleaning member that cleans the surface of the charging member, and the charging member. A means for contacting / separating with respect to the photoconductor,
In an image forming apparatus that rotates by rotating the charging member in contact with the cleaning member when the charging member is separated from the photosensitive member, the charging member is in contact with the photosensitive member.
When moving from the state to the separated state, the photoconductor is rotated while being rotated.
If the charging member is separated and the rotating direction when the charging member rotates while contacting the photosensitive member is the same as the rotating direction when rotating while contacting the cleaning member, the charging member is exposed to light. Even if the cleaning member is separated from the body while it is rotating while being in contact with the body, since the rotating direction is the same, a large shock load is generated as if it is rapidly rotated in the opposite direction. Will not be added to the drive system or the support portion of the charging member. If the charging member is rotated when coming into contact with the cleaning member, the charging member comes into contact with the cleaning member by a dynamic frictional force, so that the surface of the charging member is less likely to be damaged. The load for driving the charging member is reduced.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a plan view showing the periphery of a charging roller of an image forming apparatus for explaining an embodiment of the invention, and FIG. 2 is a schematic configuration diagram showing an image forming unit of the image forming apparatus. In the image forming apparatus shown in FIG. 2, a surface of the photoconductor 1 is applied by applying a voltage to the drum-shaped rotating photoconductor 1 which is a member to be charged and a charging roller 2 which is a charging member in direct contact therewith. 1A is a contact charging type image forming apparatus that uniformly charges 1a to a predetermined potential.
The surface of the charging roller 2 at a predetermined peripheral speed.
While they are in contact with each other, they are driven to rotate at a constant speed in the direction of the arrow by turning around.

The photosensitive member 1 includes a drum driving timing belt, a drum driving pulley, and a motor 30 for driving them.
The charging roller 2 is driven by a photosensitive member driving system (see FIG. 1), and the charging roller 2 can be separated from the surface 1a by a contacting / separating mechanism 40 described later, for example, a contact pressure of 10 g / c.
They are in contact with each other by m (contact with an approximate line). Around the photoconductor 1, an eraser 18 in addition to the charging roller 2 and a developing device 6 are provided.
A contact type transfer device 7 having an endless belt 7a and a cleaning unit 8 are provided.

Then, the light from the exposure device 9 (only the mirror portion is shown) is incident on the surface 1a of the photoconductor 1,
The charging surface uniformly charged by the charging roller 2 is exposed to form an electrostatic latent image thereon, and the electrostatic latent image is static in an area portion outside the size of the transfer paper P used by the eraser 18. The charges are removed (trimming), and the remaining electrostatic latent image is developed by the toner supplied by the developing sleeve 6a of the developing device 6 to form a toner image (visible image).
Becomes

On the other hand, the transfer paper in the paper feed cassette (not shown) is fed by a paper feed roller which rotates at a predetermined timing.
The transfer device 7 is fed out one by one, and is temporarily stopped between the registration roller 13 and the pressure roller 14 rotating in pressure contact therewith, and the timing is adjusted. Is conveyed toward the transfer section where is provided.

A transfer device 7 applies a transfer bias to the transfer paper P to transfer a toner image to the upper surface side in FIG. 2, and the toner image is separated from the photoconductor 1 and conveyed to a fixing device (not shown), where the toner is transferred. After the paper is fixed, the paper is ejected to a paper ejection tray or the like outside the apparatus. Then, the residual toner remaining on the photoconductor 1 after the transfer is completed and foreign matters such as paper dust are removed by the cleaning blade 8a provided in the cleaning unit 8, and the residual potential left on the photoconductor 1 is neutralized. Removed by a device (not shown),
Prepare for the next charging by the charging roller 2.

As shown in FIG. 1, the charging roller 2 has a conductive rubber roller portion 1 on the outside of a conductive cored bar 15 made of iron or the like.
6 are integrally mounted, and both ends of the conductive core 15 are rotatably supported by bearings 20 and 21 made of resin. The bearing 20 supports the conductive cored bar 15 of the charging roller 2 on one end side and the hole 2 formed on the other end side.
0a is rotatably fitted into the conductive support shaft 23.
Then, both ends of the support shaft 23 are supported by the power feeding side support portion 70a of the bracket 70 formed of a steel plate bent in a U shape.

Therefore, the bearing 20 rotates about the support shaft 23. The upper end 15a of the conductive cored bar 15 of the charging roller 2 in FIG. 1 is formed in a spherical shape,
The end portion 15a is in contact with the flat surface portion 27a of the power supply terminal 27. The power supply terminal 27 has a collar 27b as shown in FIGS. 3 and 4, and is provided in the hole 26a of the conductive plate 26 having a spring property as shown in FIG.
The b is pushed in until it comes into contact with the surface of the conductive plate 26, and in this state, the claw portion 26b of the conductive plate 26 prevents it from coming off.

A mounting hole 26c as shown in FIG. 3 is formed in the conductive plate 26, and a screw 71 is inserted into the mounting hole 26c as shown in FIG. The conductive plate 26 is fixed to the bearing 20 by being tightened in the screw hole 21a formed in the.

A conductive member 72 is interposed between the conductive plate 26 and the bearing 20, and an inner peripheral surface of a contact portion of the conductive member 72 extending to the charging roller 2 is provided with a conductive cored bar of the charging roller 2. It is in contact with the outer peripheral surface of 15. Then, in that state, the curl portion 26d at one end (the right end in FIG. 1) of the conductive plate 26
However, the outer peripheral surface of the support shaft 23 is brought into contact with the outer peripheral surface of the support shaft 23 with a predetermined contact pressure, and electrical continuity is established between the two. Also, at one end of the support shaft 23,
A contactor 74 having a spring property is brought into contact with the contactor 74.
Is connected to the high-voltage power supply 75, so that the high voltage from the high-voltage power supply 75 is applied to the conductive cored bar 15 of the charging roller 2.

On the other hand, the bearing 21 for rotatably supporting the lower end of the charging roller 2 in FIG.
9 is rotatably fitted, and both ends of the support shaft 29 are supported by the drive-side support portions 70b of the bracket 70. Therefore, the bearing 21 rotates about the support shaft 29. The bearing 21 includes an intermediate gear 31 and a gear 32 that meshes with the intermediate gear 31.
And are rotatably supported, and an intermediate gear 31 thereof meshes with a roller drive gear 38 fixed to one end of the conductive cored bar 15 of the charging roller 2.

The gear 32 also meshes with a transmission gear 33 fixed to one end of a gear support shaft 34 rotatably supported by the device fixing portion 10, and the other end of the gear support shaft 34 is unidirectional. A drive gear 35, which has a built-in clutch 37 and is mounted on the gear support shaft 34 via the one-way clutch 37, is provided.

Further, a driving force transmission gear 36 rotatably supported by the apparatus fixing portion 10 meshes with the driving gear 35, and the driving force transmission gear 36 is rotated by a motor 30 for driving the photoconductor 1. It is supposed to be done. In this embodiment, the roller drive gear 38,
Intermediate gear 31, gear 32, transmission gear 33, drive gear 35
A gear train in which a plurality of gears of the driving force transmission gear 36, which mesh with each other, are arranged functions as a rotational force transmission unit that transmits the rotational force from the motor 30, which is a rotational drive source, to the charging roller 2.

The one-way clutch 37 functions to reduce the surface peripheral speed when the charging roller 2 is separated from the photosensitive member 1 with respect to the surface peripheral speed when rotating while contacting the photosensitive member 1. When the charging roller 2 contacts the photoconductor 1, the rotational force from the motor 30 is stopped from being transmitted to the charging roller 2 via the rotational force transmitting means, and the charging roller 2 is separated from the photoconductor 1. At times, the rotational force from the motor 30 is transmitted to the charging roller 2 via the rotational force transmission means by connecting the gear support shaft 34 and the drive gear 35.

FIG. 5 is a schematic structural view showing the internal structure of the one-way clutch 37. The one-way clutch 37 has a predetermined linear portion 81a on the inner peripheral surface of the clutch housing 81 integrally fixed to the drive gear 35 for forming a plurality of wedge portions between the inner peripheral surface and the outer peripheral surface 34a of the gear support shaft 34. Formed along the circumferential direction at intervals of
1 and the gear support shaft 34 between the plurality of spring receiving blocks 8
3 is inserted and each spring receiving block 83 is fixed to the inner peripheral surface of the clutch housing 81, and each bearing surface 83a of the spring receiving block 83 rotatably supports the gear support shaft 34.

Further, needle rollers 85 are rotatably inserted between the spring receiving blocks 83 and 83 adjacent to each other in the circumferential direction, and the needle rollers 85 are inserted between the adjacent spring receiving blocks 83 and 83. Allow to move slightly in the circumferential direction. Then, the springs 86 are mounted in the spring receiving grooves of the spring receiving blocks 83, respectively, and the biasing force of the springs 86 biases the needle rollers 85 in the direction of arrow B in FIG.

Transmission of the rotational force of the one-way clutch 37 is carried out by utilizing the difference in rotational speed between the drive gear 35 and the gear support shaft 34. Here, with respect to the surface peripheral velocity V0 when the charging roller 2 rotates while contacting the photoconductor 1,
The gear ratios of the respective gears are set so that the peripheral surface speed V when rotating away from the photoconductor 1 becomes slow.

Now, it is assumed that the charging roller 2 is in contact with the photoconductor 1 and is being driven to rotate. In FIG. 1, assuming that the rotation direction of the photoconductor 1 is the arrow A direction, the charging roller 2
1 is rotated in the direction of arrow B in FIG. 1, and the rotation of the charging roller 2 is caused by the roller drive gear 38, the intermediate gear 31, the gear 3
2 is transmitted to the transmission gear 33. This transmission gear 3
The rotation direction of 3 is the same as the rotation direction of the photoconductor 1 (direction of arrow A), and the gear support shaft 34 is rotated in the same direction as the transmission gear 33. On the other hand, the rotational force of the motor 30 is transmitted to the drive gear 35 via the drive force transmission gear 36, and the rotational direction of the drive gear 35 is also the rotational direction of the photoconductor 1 (direction of arrow A).
In the same direction as.

When the charging roller 2 is in contact with the photoconductor 1 and is being driven to rotate, the rotation speed of the gear support shaft 34 is higher than the rotation speed of the drive gear 35. Therefore, the gear support shaft 34 rotates relative to the drive gear 35 in the direction opposite to the arrow B in FIG. As a result, each needle roller 85 rolls in the same direction against the biasing force of each spring 86.

For this reason, each needle roller 85 moves to a wide portion in the wedge portion, and the one-way clutch 3
7 is unlocked. That is, the clutch housing 81 and the gear support shaft 34 are rotatable relative to each other, and the gear support shaft 34 idles with respect to the drive gear 35.
In summary, when the charging roller 2 is in sliding contact with the photoconductor 1 and is being driven to rotate, the roller drive gear 38 of FIG.
The intermediate gear 31, the gear 32, the transmission gear 33, and the gear support shaft 34 are rotated by the rotational driving force of the photoconductor 1.

Next, when the charging roller 2 shifts from the state where it is in contact with the photosensitive member 1 to the separated state, this charging roller 2
The rotational speed of the gear support shaft 34 in the direction of arrow A decreases with the transition from the contact state to the photoconductor 1 to the separated state. On the other hand, since the drive gear 35 rotates at a constant speed in the direction of the arrow A, the rotation speed of the drive gear 35 is
4, the gear support shaft 34 rotates relative to the drive gear 35 in the direction of arrow B as shown in FIG.

Therefore, the outer peripheral surface 34 of the gear support shaft 34 is
Show each needle roller 85 that makes point contact with a.
The force to move in the direction acts. As a result, the needle roller 85 is moved to the narrow portion of the wedge portion, each needle roller 85 is strongly pressed against the outer peripheral surface 34a of the gear support shaft 34 and the straight portion 81a, and the one-way clutch 37 is locked. Become. That is, the clutch housing 81 and the gear support shaft 34 are locked by the needle rollers 85, the drive gear 35 and the gear support shaft 34 are connected, and the charging roller 2 shown in FIG. Thus, the photoconductor 1 is rotated in the opposite direction to the photoconductor 1 while being separated from the photoconductor 1, and is brought into sliding contact with a cleaning member described later.

It should be noted that the one-way clutch 37 is preferably provided in the roller drive gear 38 when there are no restrictions such as space. With this configuration, when the charging roller 2 is rotated together with the photoconductor 1, the intermediate gear 31,
Since the gear 32, the transmission gear 33, etc. are not driven, the driving load can be reduced.

Next, the contact / separation mechanism 40 for contacting / separating the charging roller 2 with respect to the photosensitive member 1 will be described with reference to FIGS. 6 to 12. Conductive core metal 1 of charging roller 2
The bearing 21 that rotatably supports the contact lever 5 has a contact lever portion 21 that protrudes from the upper surface of the bracket 70 at the upper right end in FIG.
b, and a spring engaging portion 21c is formed in the lower portion. Further, a spring engaging portion 70c is formed on the bracket 70 so as to correspond to the spring engaging portion 21c.
A tension spring 25 is attached between 1c and 70c.

Therefore, the bearing 21 is urged to rotate in the counterclockwise direction in FIG. 6 about the support shaft 29 by the urging force of the tension spring 25, whereby the charging roller 2 is rotated.
Is in contact with the surface 1a of the photoconductor 1 with a predetermined contact pressure suitable for charging, and can be rotated by the photoconductor 1.

Similarly, the bearing 20 shown in FIG. 1 is also provided with a contact lever portion 20b protruding from the upper surface of the bracket 70.
The spring engaging portions 20c are formed in the lower portions, the spring engaging portions 70d are formed in the bracket 70, and the tension spring 25 is attached between the spring engaging portions 20c and 70d. Therefore, the bearing 20 is also urged to rotate about the support shaft 23 by the urging force of the tension spring 25, so that the charging roller 2 contacts the surface 1 a of the photoconductor 1.

In the charging roller 2, when the image forming process is completed, the contact lever portion 20b of the bearing 20 and the contact lever portion 21b of the bearing 21 have the contact / separation mechanism 40 shown in FIG.
7 are simultaneously pressed by the pressing cams 50a (FIG. 9) and 50b, and are rotated clockwise as shown in FIG. 7 to separate from the surface 1a of the photoconductor 1.

At the separated position, as shown in FIG. 7, the charging roller 2 comes into contact with the cleaning member 11 fixed to the inner surface of the bracket 70, and at the moment when the charging roller 2 separates from the photosensitive member 1, The rotational force from the motor 30 described in FIG. 1 is transmitted from the driving force transmission gear 36 and the driving gear 35 to the gear support shaft 34 via the one-way clutch 37, and the rotational force is further transmitted to the transmission gear 33, the gear 32, and the intermediate gear. Gear 3
1 and the roller drive gear 38. Therefore,
While the charging roller 2 is rotated while being in contact with the photoconductor 1 described above, the surface peripheral speed V0 is instantaneously switched to a surface peripheral speed V lower than the surface peripheral speed V0 when rotating, and
Since the cleaning member 11 is brought into contact with the cleaning member 11 as shown in FIG. 5, foreign matter such as toner and paper dust attached to the surface of the charging roller 2 is reliably removed.

In the contact / separation mechanism 40 for moving the charging roller 2, the pressing cam 50a shown in FIG. 8 is used as the contact lever portion 20b (FIG. 1) of the bearing 20, and the pressing cam 50b is used as the bearing 2.
Since it is necessary to simultaneously contact the first contact lever portion 21b (FIG. 1) in the same phase, the pressing cams 50a and 50
b is formed integrally with the same release moving plate 50. The release moving plate 50 is formed with long holes 50c and 50d at intervals along the arrow C direction, which is the direction in which the pressing cams 50a and 50b contact and separate from the contact lever portions 20b and 21b, respectively. The elongated holes 50e and 50f are also formed in the arrow D direction orthogonal to the arrow C direction.

Then, the elongated holes 50c, 50d are movably fitted into pins 59, 59 vertically provided on the holding bracket 58, and L-shaped levers 51, 51 are attached to the respective pins 59.
Are rotatably fitted in the levers 51 and
Pins 91, 9 projecting downward from one end of each
1 is fitted into the long holes 50e and 50f of the release moving plate 50 and the long holes 58a and 58b also formed in the holding bracket 58, and an E-ring (not shown) is attached to the head of each pin 59 to prevent it from coming off. is doing.

Further, at the other end of each lever 51, as shown in FIG.
To the pins 92 projecting upward,
2 is fitted with elongated holes 52a and 52b formed corresponding to the respective pins 92 along the longitudinal direction, one end of the tension spring 53 is attached to the tip of each pin 92, and the other end of the tension spring 53 is linked. It is attached to each spring hooking claw 52c, 52d formed on 52.

As shown in FIG. 9, the link 52 has one end of a tension spring 54 attached to a spring hook 52e formed at one end thereof, and the other end of the tension spring 54 is attached to a spring engaging portion 58c of a holding bracket 58. By
In the figure, it is pulled and urged in the direction of arrow E. further,
One end of the drive wire 55 is fixed to the other end of the link 52, and the drive wire 55 is wound around a pulley 56 rotatably supported by a holding bracket 58 so that the tension direction is 90.
After the conversion, the other end is fixed to the tip of the swing lever 57.

As shown in FIG. 10, the swing lever 57 has a shaft 93 swingably supported at its substantially center.
In the figure, an eccentric cam 95 contacts the lower left surface 57a. Then, as described above with reference to FIG. 9, the link 52 is urged in the arrow E direction by the tension spring 54, which in turn causes the drive wire 55 to be urged in the same direction. The wire 55 is pulled and urged in the direction of arrow F to move the swing lever 57.
Is urged to rotate in the direction of arrow G, and its left surface 57a is pressed against the eccentric cam 95.

The contact / separation mechanism 40 is used for the charging roller 2
When the is separated from the photoconductor 1, the eccentric cam 95 is rotated to the position shown by the solid line in FIG. Then, the swing lever 57 rotates in the direction opposite to the arrow G, and the drive wire 55 is moved leftward in the figure, so that the link 52 shown in FIG.
Moves in the direction of arrow J. Thereby, each lever 51
11, the pin 92 moves to the right in the figure, so that the lever 51 rotates in the K direction shown in FIG. Therefore, the disengagement moving plate 50 in which the long holes 50e and 50f (FIG. 8) engage with the pin 91 fixed to each lever 51 moves in the arrow M direction.

Therefore, the pressing cam 50b moves from the position shown in FIG. 6 to the position shown in FIG.
0a (FIG. 9) also moves together, and the contact lever portion 21b of the bearing 21 and the contact lever portion 20b of the bearing 20 are simultaneously pressed by the pressing cams 50b and 50a, respectively, and are rotated to the position shown in FIG. The charging roller 2 moves away from the surface 1 a of the photoconductor 1. At this time, the charging roller 2 comes into contact with the cleaning member 11 with a predetermined pressing force by the biasing force of the tension spring 53 shown in FIG.

In this state, the one-way clutch 37 described with reference to FIGS. 1 and 5 operates (drive gear 35 and gear support shaft 3).
4) and the charging roller 2 rotates at a surface peripheral speed V lower than the surface peripheral speed V0 when rotating while being in contact with the photoconductor 1, so that in the case of an image forming apparatus having a high process linear velocity. When the charging roller is rotated at a high surface peripheral speed corresponding to the high process linear velocity, toner is fixed by the heat generated by the sliding contact of the charging roller with the cleaning member, or the surface of the charging roller is Mechanical damage is likely to occur, which can be prevented in this embodiment.

On the contrary, when the charging roller 2 is brought into contact with the photosensitive member 1, the eccentric cam 95 is rotated to the position shown by the phantom line in FIG. Then, the swing lever 57 is moved to the arrow G
9 and the drive wire 55 is returned in the opposite direction to that described above by the urging force of the tension spring 54 shown in FIG. 9, so that the link 52 moves in the same direction, whereby the pin 92 of each lever 51 is moved. Moves to the left in the figure as shown in FIG.

Therefore, each lever 51 shown in FIG. 9 rotates in the direction opposite to the arrow K, and the release moving plate 50 moves in the direction opposite to the arrow M. Thereby, the pressing cam 50
Since a and 50b move from the position of FIG. 7 to the position of FIG. 6 and separate from the contact lever portions 20b and 21b, respectively, the charging roller 2 comes into contact with the surface 1a of the photoconductor 1 again.

FIGS. 13 and 14 are schematic views similar to FIGS. 6 and 7 for explaining a different embodiment of the present invention, and the portions corresponding to FIGS. 6 and 7 are designated by the same reference numerals. I am doing it. This embodiment differs from the embodiments described with reference to FIGS. 6 and 7 in that the bearing 21 is provided with a gear so that only the roller drive gear 38 can rotate, and
As shown in FIG. 4, when the charging roller 2 is moved to a position separated from the photoconductor 1, the transmission gear 33 'is arranged at a position where the roller drive gear 38 meshes with the transmission gear 33'.
The transmission gear 33 'is fixed to the device fixing portion (see 10 in FIG. 1).
It is a point rotatably attached to.

The transmission gear 33 'is similar to the transmission gear 33 described with reference to FIG. 1 and is different from the embodiment of FIG. 1 only in the disposition position. The transmission gear 33' is fixed at one end. Similarly, the gear support shaft 34 is attached to the drive gear 35 via the one-way clutch 37 as shown in FIG. When the transmission gear 33 'and the roller driving gear 38 are in mesh with each other as shown in FIG. 14, the charging roller 2 contacts the photoconductor 1 as in the embodiment described with reference to FIGS. While rotating, the surface peripheral speed V0 is lower than the surface peripheral speed V0. Also according to this embodiment, the same effect as that of the above-described embodiment can be obtained.

FIGS. 15 to 19 are drawings for explaining a further different embodiment of the present invention, and the portions corresponding to those in FIGS. 1 and 6 are designated by the same reference numerals. In this embodiment, two pulleys 46 and 67 are used instead of gears as a rotational force transmitting means, and a belt 68 is provided between the pulleys.
Are using. That is, as shown in FIG. 15, the image forming apparatus according to the present embodiment includes the device fixing portions 10 and 1.
The roller support shaft 5 is rotatably supported between 0 ', and the roller support shaft 5 has the other end side of the bearing 20 on the power feeding side on the roller support shaft 5 (right side in FIG. 15).
And the base portion on the other end side of the drive side bearing 21 are fixed to each other.

End of drive side of roller support shaft 5 (downward in the figure)
A lever 43 for releasing pressure contact of the charging roller 2 to the photoconductor 1 is fixed to the front side of the lever 43 from the fixing portion to the roller support shaft 5 in FIG. 15 (upper side in the apparatus). The engaging projection 43a is formed at a distance from the engaging projection 43a, and the engaging portion formed at the tip of the movable rod 44a of the solenoid 44 is engaged with the engaging projection 43a.

Further, torsion coil springs 45, 45 for urging the rotation are mounted on the roller support shaft 5 so as to correspond to the inner sides of the bearings 20 and 21, respectively. One end (inside) of each of the torsion coil springs 45, 45 is fixed to a fixing portion of a device (not shown), and the other end thereof is engaged with or fixed to the base portion of the bearing 20, 21, respectively. .

Therefore, the roller support shaft 5 is rotationally biased in the direction in which the charging roller 2 is in contact with the surface of the photoconductor 1 by the biasing force of the two torsion coil springs 45, 45. The lever 43 is rotated around the roller support shaft 5, and when the movable rod 44a is moved in the X direction shown by the arrow in FIG. 15 (the solenoid 44 is turned on), the charging roller 2 moves away from the photoconductor 1. The roller support shaft 5 rotates.

On the contrary, when the solenoid 44 is turned off,
The movable rod 4 is driven by the rotational biasing force of the torsion coil spring 45.
4a returns in the direction opposite to the arrow X, the roller support shaft 5 is rotated in the opposite direction, and the charging roller 2 contacts the photoconductor 1. A pulley 46 is fixed to an end of the charging roller 2 on the drive side of the conductive core 15 via a one-way clutch 49. An output gear 47 is fixed to the rotating shaft of the motor 30, and the output gear 47 meshes with the drive gear 48. The drive gear 48 is rotatably supported by a shaft 66.

The shaft 66 is rotatably supported by a fixed portion of the apparatus. A pulley 67 is rotatably attached to the shaft 66, and the pulley 67 is integrally fixed to the drive gear 48. A belt 68 is stretched between the pulley 67 and the pulley 46. One-way clutch 4
9 transmits the rotational force from the motor 30 to the charging roller 2, but the rotational force from the opposite charging roller 2 is transmitted to the motor 30.
It serves to cut off the transmission to.

In this image forming apparatus, the charging roller 2 is shown in FIG.
As shown in FIG. 6, when the photoconductor 1 is contacted, the charging roller 2
As shown in FIG. 17, the rotational force from the photoconductor 1 rotates in the direction of the arrow. At this time, the rotational force from the charging roller 2 is not transmitted to the pulley 46 and subsequent parts in FIG. 15 by the one-way clutch 49, so that the pulley 46 idles.

Next, the solenoid 44 shown in FIG.
When set to N, the movable rod 44a moves in the arrow X direction, and the lever 43 moves in the same direction, whereby the bearings 20 and 21 rotate in the clockwise direction in FIG. 17 together with the roller support shaft 5. Therefore, the charging roller 2 is
And as shown in FIG. 19, it is separated from the photoconductor 1 and contacts the cleaning member 11 with a predetermined pressure.

At that time, at the moment when the charging roller 2 separates from the surface of the photosensitive member 1, the rotational force from the motor 30 shown in FIG. 15 is transmitted to the output gear 47, the drive gear 48, and further to the pulley 67. The rotational force is transmitted to the pulley 46 by the belt 68, and the rotational force is transmitted to the conductive cored bar 15 of the charging roller 2 via the one-way clutch 49. Therefore, the charging roller 2 contacts the cleaning member 11 while rotating in the same rotation direction as the charging roller 2 rotates while contacting the photoreceptor 1.

The rotation of the charging roller 2 at this time rotates at a surface peripheral speed V slower than the surface peripheral speed V0 when the charging roller 2 rotates while contacting the photosensitive member 1. Therefore, as in the case of each of the embodiments described with reference to FIGS. 1 to 14, in the case of an image forming apparatus having a high process linear velocity,
When the charging roller is rotated at a high surface peripheral speed corresponding to the high process linear velocity, toner is fixed due to heat generated by the charging roller slidingly contacting the cleaning member, or the surface of the charging roller is mechanically fixed. Although such damage is likely to occur, this embodiment can also prevent it.

Finally, the optimum surface peripheral speed of the charging roller when cleaning the charging roller will be described. The number of times the roller surface is rubbed is N, which is derived from the mechanical durability of the charging roller surface.
When t, the outer diameter of the charging roller is d, and the total cleaning time of the charging roller is ΣT, the optimum surface peripheral velocity Vc of the charging roller during cleaning is given by the following equation. Vc = π · d · Nt / ΣT By setting the optimum surface peripheral speed during cleaning of the charging roller near the value of Vc obtained by the above formula, stable long-term without impairing the durable life of the charging roller The roller cleaning performance can be maintained.

In each of the above-described embodiments, the driving force from one motor 30 is transferred to the photosensitive member 1 and the rotational force transmitting means including a plurality of gears such as the driving gear 35, or the pulley 4.
Although they are transmitted to the rotational force transmission means using the belts 67 and 67 and the belt 68, they may be driven by separate motors. Further, in each of the embodiments described above, when the charging roller 2 is brought into contact with the photoconductor 1, the charging roller 2 is rotated in the direction opposite to the rotation direction of the photoconductor 1 (the direction in which the photoconductor 1 rotates). It is good to do so.

That is, the charging roller 2 is connected to the motor 30.
(See FIG. 1) Rotate from the position shown in FIG. 7 to the position in contact with the photoconductor 1 shown in FIG. 6 or from the position shown in FIG. 18 to the position in contact with the photoconductor 1 shown in FIG. Then, immediately after the charging roller 2 comes into contact with the photoconductor 1, the driving by the motor 30 may be stopped, and the charging roller 2 may be switched to the rotation drive by the photoconductor 1. Then, the charging roller 2 comes into contact with the photoconductor 1 while rotating, so that the surface of the charging roller 2 can be prevented from being locally worn. Further, since the charging roller 2 and the photoconductor 1 come into contact with each other with a dynamic frictional force smaller than the static frictional force, damage to the surface of the photoconductor 1 can be prevented.

[0075]

As described above, according to the image forming apparatus of the present invention, even when the process linear velocity is high,
Since the surface peripheral speed when the charging member is in contact with the cleaning member can be made slower than that when the charging member is rotating while being in contact with the photoconductor, heat generated when the charging member makes sliding contact with the cleaning member is reduced. Toner sticks to the surface of the charging member,
Prevents the surface of the charging member from being mechanically damaged,
The charging member can be effectively cleaned.

If the charging member is rotated in the direction opposite to the rotation direction of the photosensitive member when the charging member is brought into contact with the photosensitive member, the charging member contacts the photosensitive member while rotating. As a result, it is possible to prevent local abrasion of the surface of the charging member, and the charging member and the photoconductor come into contact with each other with a dynamic friction force smaller than the static friction force, so that the surface of the photoconductor is not damaged. It can be prevented. Further, the charging member,
Even if the charging member is rotated when coming into contact with the cleaning member, the charging member also comes into contact with the cleaning member by the dynamic frictional force, so that the surface of the charging member is less likely to be damaged. Moreover, the load for driving the charging member is also reduced.

Further, if the rotating direction when the charging member rotates while contacting the photosensitive member and the rotating direction when the charging member rotates while contacting the cleaning member are the same, When the charging member is in contact with the photoconductor and the cleaning member is in contact with the photoconductor, the charging member is in contact with the photoconductor and the cleaning member. Since the rotation directions of the charging member are the same, a large shock load is not applied to the drive system and the supporting portion of the charging member unlike when the members are rapidly rotated in the opposite directions. It is possible to prevent deterioration due to abrasion of the surface and the supporting portion. Moreover, the load required to drive the charging member can be reduced.

Further, if the speed reducing means is provided with the rotational force transmitting means and the one-way clutch, the surface peripheral speed of the charging member can be instantaneously switched by the one-way clutch. Noise such as switching noise can be prevented. Further, if the photoconductor is used as a rotary drive source that rotationally drives the charging member when the charging member is brought into contact with the photoconductor, a new driving force transmission means is provided for driving the charging member during image formation. Since it can be carried out by contact drive (coincident rotation) by the photoconductor, uniform and uniform charging can be carried out by the most natural and effective method.

[Brief description of drawings]

FIG. 1 is a plan view showing the periphery of a charging roller of an image forming apparatus for explaining an embodiment of the invention.

FIG. 2 is a schematic configuration diagram showing an image forming unit of the image forming apparatus.

3 is a perspective view showing a conductive plate 26 for power supply and a power supply terminal 27 for applying a high voltage to the charging roller of FIG.

FIG. 4 is a plan view showing a state where the power supply terminal 27 is assembled to the conductive plate 26 in the same manner.

FIG. 5 is a schematic configuration diagram showing an internal configuration of a one-way clutch that transmits a driving force to a charging roller.

6 is a cross-sectional view taken along the line BB of FIG. 1 showing a state where the charging roller is brought into contact with the photoconductor by the contact / separation mechanism provided in the image forming apparatus of FIG.

FIG. 7 is a sectional view taken along line BB in FIG. 1, showing a state in which the charging roller is also separated from the photoconductor.

FIG. 8 is an exploded perspective view for explaining the contact / separation mechanism of the same.

9 is a perspective view showing an assembled state of the contact / separation mechanism of FIG.

FIG. 10 is a schematic view showing the periphery of an eccentric cam that also drives the contact / separation mechanism.

FIG. 11 is a plan view showing the positional relationship between the lever of the contact / separation mechanism and the elongated hole provided in the link when the charging roller is separated from the photoconductor.

FIG. 12 is a plan view showing the positional relationship between the lever of the contact / separation mechanism and the slot provided in the link when the charging roller is in contact with the photoconductor.

FIG. 13 is a schematic view similar to FIG. 6 for explaining a different embodiment of the present invention.

FIG. 14 is a schematic view similar to FIG. 7 in the same embodiment.

FIG. 15 is a plan view similar to FIG. 1, showing the periphery of a charging roller of an image forming apparatus, for explaining still another embodiment of the present invention.

FIG. 16 is a sectional view taken along line CC of FIG. 15 showing a state where the charging roller is in contact with the photoconductor in the same embodiment.

FIG. 17 is a sectional view taken along line D-D of FIG. 15 showing a state where the charging roller is in contact with the photoconductor in the same embodiment.

FIG. 18 is a sectional view taken along line C-C of FIG. 15 showing a state where the charging roller is separated from the photoconductor in the same embodiment.

FIG. 19 is a sectional view taken along line DD of FIG. 15, showing a state in which the charging roller is separated from the photoconductor in the same embodiment.

FIG. 20 is a schematic view showing an example of a conventional contact charging type charging device.

[Explanation of symbols]

1: photoconductor 2: charging roller (charging member) 11: Cleaning member 30: Motor 31: Intermediate gear 32: Gear 33: Transmission gear 34: Gear support shaft 35: Drive gear 37, 49: One-way clutch 40: Contact / separation mechanism 46, 67: Pulley 47: Output gear 48: Drive gear 68: Belt

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (11)

(57) [Claims] 1. A rotating photosensitive member, a charging member that contacts the photosensitive member and rotates in a direction opposite to the rotating direction of the photosensitive member to uniformly charge the surface thereof, and a charging member of the charging member. A state in which a cleaning member for cleaning the surface and means for contacting / separating the charging member with respect to the photoconductor are provided, and the charging member is brought into contact with the cleaning member when the charging member is separated from the photoconductor In the image forming apparatus in which the cleaning is performed by rotating the charging member with the
When the charging member moves to the state, the charging member is rotated and separated from the charging member.
The image forming apparatus is provided with a decelerating unit that slows down the surface peripheral speed of the charging member at the time of rotation relative to the surface peripheral speed when the charging member rotates while contacting the photoconductor. 2. The image forming apparatus according to claim 1, wherein the charging member rotates in a direction opposite to a rotating direction of the photoconductor when the charging member contacts the photoconductor. 3. The image forming apparatus according to claim 1, wherein the charging member rotates when coming into contact with the cleaning member. 4. The rotating direction when the charging member rotates while contacting the photoconductor and the rotating direction when the charging member rotates while contacting the cleaning member are the same. The image forming apparatus according to item 1. 5. A rotational force transmission means for transmitting, to the charging member, a rotational force from a rotary drive source that rotationally drives the charging member when the deceleration means separates the charging member from the photoconductor. When the charging member is in contact with the photoconductor, the rotational force from the rotary drive source is stopped from being transmitted to the charging member via the rotational force transmitting means, and when the charging member is separated from the photoconductor. The image forming apparatus according to claim 1, further comprising a one-way clutch that transmits the rotational force from the rotational drive source to the charging member via the rotational force transmission unit. 6. The photosensitive member is used as a rotary drive source for rotating the charging member when the charging member is brought into contact with the photosensitive member. The image forming apparatus according to item 1. 7. The image forming apparatus according to claim 5, wherein the rotational force transmitting means is a gear train in which a plurality of gears meshing with each other are arranged. 8. The image forming apparatus according to claim 5, wherein the rotational force transmitting means includes a plurality of pulleys and a belt stretched between the pulleys. 9. The image forming apparatus according to claim 1, wherein the charging member is brought into contact with the photosensitive member while rotating the charging member in a direction opposite to a rotating direction of the photosensitive member. 10. A rotating photoconductor, a charging member that rotates while being in contact with the photoconductor to uniformly charge the surface thereof, a cleaning member that cleans the surface of the charging member, and the charging member. And a means for bringing the charging member into contact with and separating from the photosensitive member, and when the charging member is separated from the photosensitive member, the charging member is rotated while being in contact with the cleaning member to perform cleaning. , The charging member is separated from the state in which the charging member is in contact with the photosensitive member.
And a rotation direction when the charging member rotates while being in contact with the photoconductor, and a rotation direction when rotating while being in contact with the cleaning member. An image forming apparatus characterized in that and are the same. 11. The charging member is rotated when coming into contact with the cleaning member.
The image forming apparatus according to item 0.