JP2019060992A - Charging device and image forming apparatus using the same - Google Patents

Abstract

To reduce the amount of distortion associated with contact between a charging member and a cleaning member when the charging member is stopped, while ensuring cleaning performance of the cleaning member for the charging member.SOLUTION: A charging device comprises a position variable mechanism 3 that changes a contact position of a cleaning member 2 with a charging member 1 in the circumferential direction. The position variable mechanism includes: a guide member 4 that has a guide groove 5 in which the cleaning member 2 is guided between a first contact position on which a first contact pressure p1 acts and a second contact position on which a second contact pressure p2 acts as the contact position of the cleaning member 2, and retractably supports the cleaning member 2 between the first contact position and second contact position along the guide groove 5; and an urging element 6 that urges the cleaning member 2 from the first contact position toward the second contact position. The position variable mechanism moves the cleaning member 2 from the second contact position to the first contact position against an urging force of the urging element 6 with a frictional force F generated at a contact part between the charging member 1 and cleaning member 2 when the charging member 1 is driven.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charging device and an image forming apparatus using the same.

Conventionally, as the charging device of this type, for example, those described in Patent Documents 1 and 2 are already known.
In Patent Document 1, the contact resistance is low on the inner wall of the bearing hole on the side near the charging roll, and the contact resistance is high on the inner wall of the bearing hole on the side far from the charging roll. Requires a large force, and on the contrary, does not require a force for the movement of the cleaning member in contact with the charging roll, thereby preventing the cleaning member from jumping up without using a pressing force of a spring member or the like. A cleaning device capable of reliably cleaning the surface of the charging roll with a simple configuration is disclosed.
In Patent Document 2, in order to provide a charging device that makes the nip pressure between the cleaning roll and the charging roll uniform in the axial direction, the image carrier is rotated by being in contact with the image carrier that carries the image. The charging roll and the cleaning roll which is formed longer than the axial length of the charging roll and rotates while contacting the charging roll to clean the charging roll, the outer diameter decreases at both ends in the axial direction of the charging roll An outer diameter reducing portion is provided, and on both sides in the axial direction of the charging roll and the cleaning roll, the cleaning roll is in pressure contact with the charging roll and charging is performed so that the relative position between the charging roll and the cleaning roll becomes constant in the axial direction. A bearing means is provided with a bearing hole for rotatably supporting the roll shaft and the cleaning roll shaft, and the cleaning roll Bearing hole shift is supported is disclosed a charging device is long hole.

JP 2007-193247 A (Best mode for carrying out the invention, FIG. 4) JP 2013-167913 A (Best mode for carrying out the invention, FIG. 4)

  The technical problem to be solved by the present invention is charging in the aspect provided with the cleaning member that rotates following the charging member, compared to the case where the contact position of the cleaning member in the circumferential direction of the charging member is uniformly set. An object of the present invention is to suppress the amount of distortion caused by the contact between the charging member and the cleaning member when the charging member is stopped while securing the cleaning performance of the cleaning member with respect to the member.

  According to the first aspect of the present invention, there is provided a charging member provided opposite to the member to be charged, extending in the axial direction, and extending in the axial direction along the charging member, and charging member for rotating and charging the member to be charged A cleaning member that follows and rotates by coming into contact with the member and that cleans the charging member, and the charging member based on a predetermined first contact pressure of the cleaning member against the charging member when the charging member is driven A position changing mechanism for changing a contact position of the cleaning member with respect to a circumferential direction of the charging member such that a second contact pressure of the cleaning member with respect to the charging member at the time of stop becomes smaller; The cleaning member is predetermined between a first contact position on which the first contact pressure acts as a contact position of the cleaning member and a second contact position on which the second contact pressure acts. On the movement track A guide member having a guide groove for guiding the guide member, the guide member supporting the cleaning member between the first contact position and the second contact position along the guide groove, and the first member And a biasing element for biasing the cleaning member from the contact position to the second contact position, the friction force generated at the contact portion between the charging member and the cleaning member when the charging member is driven. The charging device is characterized in that the cleaning member is moved from the second contact position to the first contact position against the biasing force of the biasing element.

According to a second aspect of the present invention, in the charging device according to the first aspect, the radius of the charging member (non-contacting with the cleaning member) is r1, the radius of the cleaning member (non-contacting with the charging member) r2. Assuming that the center distance between the charging member and the cleaning member at the contact position is A, the center distance between the charging member and the cleaning member at the second contact position is B, and r1 + r2 is C,
It is a charging device characterized by satisfying A <B <r1 + r2 = C.
The invention according to claim 3 is the charging device according to claim 2, wherein the first bite amount h1 of the cleaning member at the first contact position is C-A, and the cleaning member at the second contact position Assuming that the second bite amount h2 is C-B,
It is a charging device characterized by satisfying h1> h2.
According to a fourth aspect of the present invention, in the charging device according to the third aspect, assuming that the moving amount of the cleaning member from the first contact position to the second contact position is D, at least a difference in biting amount between the two. The charging device is selected to secure Δh (= h1−h2).
According to a fifth aspect of the present invention, in the charging device according to the third aspect, the second bite amount h2 of the cleaning member at the second contact position is at least when the cleaning member is driven to rotate when the charging member is driven. The charging device is characterized in that it is set to be equal to or more than the required driven limit bite amount.
The invention according to claim 6 is the charging device according to any one of claims 1 to 5, wherein the guide member is relative to a reference line connecting the centers of the charging member and the cleaning member when the charging member is stopped. A charging device characterized by having a linear guide groove inclined at a non-right angle.
According to a seventh aspect of the present invention, in the charging device according to the sixth aspect, when the moving amount of the cleaning member from the first contact position to the second contact position is D, the guide groove is the cleaning member. The charging device is characterized in that the movement amount D of the toner is allowed.
According to an eighth aspect of the present invention, in the charging device according to the seventh aspect, any one end position of the guide groove regulates the first contact position or the second contact position of the cleaning member. It is a charging device that is characterized.
The invention according to claim 9 is the charging device according to claim 7, wherein the guide groove has a position halfway through to one end position is a first contact position of the cleaning member. It is.
The invention according to claim 10 is the charging device according to any one of claims 1 to 9, wherein the biasing element forms the guide groove substantially in the vertical direction, and the second contact position corresponds to the third one. The charging device is characterized in that gravity is used as a biasing force by being disposed below the contact position 1.
The invention according to claim 11 is the charging device according to any one of claims 1 to 10, wherein the guide member doubles as a bearing member of the cleaning member.

  The invention according to claim 12 comprises a chargeable body and a charging device for charging the body, wherein the charging device is provided opposite to the body and extends in the axial direction. A charging member which rotates to charge the body to be charged; a cleaning member which extends axially along the charging member and follows the contact with the charging member so as to follow and rotate and clean the charging member; The second contact pressure of the cleaning member against the charging member when the charging member is stopped is smaller than the predetermined first contact pressure of the cleaning member against the charging member when the charging member is driven. And a position changing mechanism for changing the contact position of the cleaning member with respect to the circumferential direction of the charging member, wherein the position changing mechanism is a first contact position at which the first contact pressure acts as the contact position of the cleaning member. And the above The cleaning member has a guide groove guided along a predetermined movement path between the second contact position where the second contact pressure acts and the first contact position along the guide groove. A guide member that supports the cleaning member between the second contact position and the second contact position, and a biasing element that biases the cleaning member from the first contact position toward the second contact position. , And the first contact from the second contact position against the biasing force of the biasing element by the frictional force generated at the contact portion between the charging member and the cleaning member when the charging member is driven. The image forming apparatus is characterized in that the cleaning member is moved to a position.

According to the first aspect of the present invention, in the aspect provided with the cleaning member that rotates following the charging member, compared to the case where the contact position of the cleaning member in the circumferential direction of the charging member is uniformly set, While ensuring the cleaning performance of the cleaning member, it is possible to suppress the amount of distortion caused by the contact between the charging member and the cleaning member when the charging member is stopped.
According to the invention of claim 2, by selecting the biting amount of the cleaning member at the first contact position and the second contact position in a predetermined relationship, the cleaning performance of the cleaning member and the charging member at the stop time It is possible to simultaneously suppress the amount of distortion caused by the contact between the charging member and the cleaning member.
According to the third aspect of the present invention, the movement amount of the cleaning member from the first contact position to the second contact position in consideration of the difference in the bite amount of the cleaning member at the first contact position and the second contact position. Can be selected.
According to the fourth aspect of the present invention, it is possible to stably rotate the cleaning member at the second contact position when the charging member is driven.
According to the invention of claim 5, by supporting the cleaning member so as to be movable in a predetermined linear direction, the cleaning performance of the cleaning member and the contact between the charging member and the cleaning member when the charging member is stopped can be obtained. The suppression of the accompanying distortion amount can be compatible.
According to the invention of claim 6, by supporting the cleaning member movably in the predetermined linear direction, the cleaning performance of the cleaning member and the contact between the charging member and the cleaning member when the charging member is stopped are provided. The suppression of the accompanying distortion amount can be compatible.
According to the seventh aspect of the present invention, the length necessary for the guide groove of the guide member can be selected in consideration of the amount of movement of the cleaning member.
According to the eighth aspect of the present invention, the cleaning member can be brought into contact with the charging member at a fixed position by restricting the cleaning member to the first contact position or the second contact position.
According to the ninth aspect of the present invention, even if the cleaning member has variations in hardness or changes with time, the cleaning member can be brought into contact with the charging member at a first contact position with a constant load.
According to the tenth aspect of the present invention, it is possible to construct a position variable mechanism utilizing gravity without using a biasing member which is a separate part as the biasing element.
According to the invention of claim 11, compared with the case of using the guide member separately from the bearing member, the position variable mechanism can be constructed with a simple configuration.
According to the invention as set forth in claim 12, in the charging device provided with the cleaning member which rotates following the charging member, the charging member is compared with the case where the contact position of the cleaning member in the circumferential direction of the charging member is uniformly set. Thus, it is possible to construct an image forming apparatus capable of suppressing the amount of distortion caused by the contact between the charging member and the cleaning member when the charging member is stopped, while securing the cleaning performance of the cleaning member for the above.

FIG. 1 is an explanatory view showing an outline of an embodiment of an image forming apparatus incorporating a charging device to which the present invention is applied. FIG. 1 is an explanatory view showing an entire configuration of an image forming apparatus according to Embodiment 1; (A) is explanatory drawing which shows the principal part of the charging device used by this Embodiment, (b) is the arrow line view seen from the B direction in (a). (A) is an explanatory view showing a positional relation between the charging roll and the cleaning roll at the time of driving the charging roll, (b) is an explanatory view showing a positional relation between the charging roll and the cleaning roll when the charging roll is not driven (at the time of stop) It is. (A) is an explanatory view showing the biting amount and contact pressure of the cleaning roll on the charging roll when the charging roll is driven, and (b) is the biting amount of the cleaning roll on the charging roll when the charging roll is not driven (C) is an explanatory view showing the relationship between the amount of biting into the charging roll and the contact pressure between the two. (A) is an explanatory view showing a method of selecting a length necessary for the guide groove of the guide plate in the position variable mechanism used in the present embodiment, (b) is an urging force of an urging spring in the position variable mechanism and charging It is an explanatory view showing the relation between the frictional force which arises in the contact area of the charging roll and the cleaning roll at the time of roll drive. The charging apparatus which concerns on the form 1 of a comparison is shown, (a) is explanatory drawing which shows the positional relationship of a charging roll and a cleaning roll at the time of charging roll drive, (b) is a charging roll at the time of charging roll non-driving (at the time of stop). It is explanatory drawing which shows the positional relationship of and a cleaning roll. The charging apparatus which concerns on Embodiment 2 is shown, (a) is explanatory drawing which shows the positional relationship of a charging roll and a cleaning roll at the time of charging roll drive, (b) is a charging roll and cleaning roll at the time of charging roll non-driving. It is explanatory drawing which shows the positional relationship of. The charging apparatus which concerns on Embodiment 3 is shown, (a) is explanatory drawing which shows the positional relationship of a charging roll and a cleaning roll at the time of charging roll drive, (b) is a charging roll at the time of charging roll non-driving (at the time of stop). It is explanatory drawing which shows the positional relationship of and a cleaning roll. (A) is explanatory drawing which shows the principal part of the charging device which concerns on the form 1 of modification, (b) is explanatory drawing which shows the principal part of the charging device which concerns on the modification 2 form. FIG. 6 is an explanatory view showing a relationship between a contaminating muscle grade (contaminated muscle G), a stored muscle grade (stored muscle G), and a bite amount in the charging device according to Example 1;

Outline of Embodiment FIG. 1 is an explanatory view showing an outline of an embodiment of an image forming apparatus incorporating a charging device to which the present invention is applied.
In the figure, the image forming apparatus includes a chargeable member 11 and a charging device 12 for charging the member 11. The charging device 12 is provided opposite to the member 11 to be charged. The charging member 1, which extends in a direction and rotates to charge the member 11 to be charged, extends axially along the charging member 1 and contacts the charging member 1 to follow and rotate and clean the charging member 1 The second contact pressure of the cleaning member against the charging member 1 when the charging member 1 is stopped than the predetermined first contact pressure p1 of the cleaning member 2 against the charging member 1 when the charging member 1 is driven a position changing mechanism 3 for changing the contact position of the cleaning member 2 with respect to the circumferential direction of the charging member 1 so that p2 becomes smaller, the position changing mechanism 3 serving as a contact position of the cleaning member 2; First contact position where p1 acts The cleaning member 2 has a guide groove 5 which is guided along a predetermined movement trajectory between the PT 1 and a second contact position PT 2 where the second contact pressure p 2 acts. Along the guide member 4 for supporting the cleaning member 2 so as to be able to advance and retract between the first contact position PT1 and the second contact position PT2, and cleaning from the first contact position PT1 to the second contact position PT2 A biasing element 6 for biasing the member 2, wherein the frictional force F generated at the contact portion between the charging member 1 and the cleaning member 2 when the charging member 1 is driven resists the biasing force of the biasing element 6 The cleaning member 2 is moved from the second contact position PT2 to the first contact position PT1.

In such a technical means, the charging member 1 may be provided so as to exert a charging action with the member 11 to be charged, and in addition to the aspect in which the member 11 is in contact with the member 11 to be charged Also include the following embodiments.
In addition, although the charging member 1 is often employed to follow and rotate the member 11 to be charged, it may be driven to rotate. However, non-rotating charging members (such as corotrons) are not included.
Furthermore, the cleaning member 2 widely includes a roll-shaped member and a spirally wound band made of urethane foam, as long as the surface is in contact with the charging member 1 and rotates following. Moreover, the aspect by which the cleaning member 2 is auxiliary | assistantly driven, for example, for slip prevention is also included.
Further, the first and second contact positions PT1 and PT2 causing the position changing mechanism 3 to exert the first contact pressure p1 and the second contact pressure p2 by the cleaning member 2 are different in the circumferential direction of the charging member 1 Need to be In this example, since "the contact position with respect to the circumferential direction of the charging member 1" is focused, for example, the one "with respect to the radial direction of the charging member 1" disclosed in Patent Document 2 is excluded.
Furthermore, the guide groove 5 is not limited to a linear shape, and includes a curved shape. For this reason, the cleaning member 2 is not limited to the aspect movable in one direction, and may be movable in a curving direction.
Furthermore, as for the biasing element 6, in addition to the biasing member such as the biasing spring, the embodiment also includes a mode using gravity (a mode in which the guide groove is formed in the action direction of gravity).

Next, a representative aspect or a preferable aspect of the charging device 12 according to the present embodiment will be described.
First, as a typical aspect satisfying the relationship between the first contact pressure p1 and the second contact pressure p2 by the cleaning member 2, the radius of the charging member 1 (without contacting the cleaning member 2) is r1, the cleaning member 2 ( Radius r2 of the charging member 1 and non-contact), A distance between the centers of the charging member 1 and the cleaning member 2 at the first contact position A, and center-to-center distance between the charging member 1 and the cleaning member 2 at the second contact position Assuming that the distance is B and r1 + r2 is C, A <B <r1 + r2 = C may be satisfied. In this example, the distance between the centers of the cleaning member 2 with the charging member 1 at the first contact position PT1 and the second contact position PT2 changes. It is intended to be defined in terms of quantities.

Moreover, as a selection method of the bite amount of the cleaning member 2, the first bite amount h1 of the cleaning member 2 at the first contact position is C-A, and the second bite amount h2 of the cleaning member at the second contact position If c−B, h1> h2 may be satisfied.
Furthermore, as another method of selecting the amount of biting in the cleaning member 2, assuming that the amount of movement of the cleaning member 2 from the first contact position to the second contact position is D, at least the difference in biting amount Δh (= It may be selected to secure h1-h2).
Furthermore, as a method of selecting the amount of biting in the cleaning member 2, the second amount of biting in h2 of the cleaning member 2 at the second contact position is necessary for the cleaning member 2 to rotate at least when the charging member 1 is driven. The aspect set up more than a driven limit bite amount is mentioned. This example shows matters to be considered in selecting the second bite amount h2.

Further, in the present embodiment, as a preferable guide groove structure of the guide member 4, it is inclined at a non-perpendicular angle to a reference line connecting the centers of the charging member 1 and the cleaning member 2 when the charging member 1 is stopped. The aspect which has the linear guide groove 5 is mentioned. In this embodiment, the guide groove 5 has a linear shape which is inclined at a non-perpendicular angle to the reference line described above.
Furthermore, as another preferable guide groove structure of the guide member 4, assuming that the movement amount of the cleaning member 2 from the first contact position to the second contact position is D, the guide groove 5 is the movement amount D of the cleaning member 2 Need to tolerate. In this example, it is possible to determine the required length of the guide groove 5 by the amount of movement of the cleaning member 2 and the inclination angle of the guide groove 5.
Moreover, as a further preferable guide groove structure of the guide member 4, the aspect which the 1st contact position or 2nd contact position of the cleaning member 2 controls the termination | terminus position of any of the guide grooves 5 is mentioned. In this example, at least any one end position of the guide groove 5 regulates the first contact position or the second contact position, and the first contact of the cleaning member 2 at both end positions of the guide groove 5. Of course, the position and the second contact position may be regulated.

Furthermore, as another preferable guide groove structure of the guide member 4, there is a mode in which a position halfway to one end position of the guide groove 5 is the first contact position of the cleaning member 2. This example shows an aspect in which the first contact position of the cleaning member 2 is not restricted to the end position of the guide groove 5.
Furthermore, as an aspect utilizing gravity as the biasing element 6, the guide groove 5 is formed substantially in the vertical direction, and the second contact position is disposed below the first contact position. There is an aspect in which gravity is used as a biasing force. The present example is an aspect in which gravity can be used as the biasing element 6 by devising the layout of the first contact position and the second contact position.
Moreover, as a preferable aspect of the position variable mechanism 3, the aspect in which the guide member 4 doubles as the bearing member of the cleaning member 2 can be mentioned. Furthermore, the guide member 4 may be integrated with the bearing member of the charging member 1.

実 施 Embodiment 1
-Overall configuration of image forming apparatus-
FIG. 2 shows the entire configuration of the first embodiment of the image forming apparatus to which the present invention is applied.
In the present embodiment, the image forming apparatus 31 has a charging device 33 for charging the photosensitive member 32 around the photosensitive member 32 as an image carrier and a latent image on the photosensitive member 32 charged by the charging device 33. A latent image writing device 34 for writing an image, a developing device 35 for developing the latent image on the photosensitive member 32 written by the latent image writing device 34 with toner and visualizing the latent image, and the developing device A transfer device 36 for transferring the toner image visualized at 35 onto the recording medium 40, for example, a transfer roll, and the photosensitive member 32 after transfer by the transfer device 36 toward the toner's original polarity direction A pre-cleaning charging device 37 for charging and a cleaning device 38 for cleaning residual toner on the photosensitive member 32 after transfer are provided.

In the present example, known electrophotographic devices can be widely adopted.
Details of the charging device 33 will be described later, and other devices will be briefly described.
First, as the latent image writing device 34, for example, a laser beam irradiation method by a laser scanning device may be adopted, or an LED array may be used instead of the laser scanning device.
Further, the developing device 35 adopts a method using a two-component developer including toner and carrier, and a developing roller 352 is provided at a position facing the photosensitive member 32 in the developing container 351 and the back of the developing roller 352 Are provided with two stirring and conveying members 353 and 354 for stirring and conveying the developer in the vertical direction, and the development collected from the developing roller 352 between the developing roll 352 and the lower stirring and conveying member 354 is further provided. A conveying member 355 for guiding the agent to the stirring and conveying member 354 is provided. Therefore, the developer is sufficiently mixed and stirred by the two stirring and conveying members 353 and 354 provided in the vertical direction, and the charged developer is supplied from the upper stirring and conveying member 353 onto the developing roller 352. The developer supplied onto the developing roll 352 is regulated in layer thickness by a layer thickness regulating member (not shown), etc., and is conveyed to a developing area which is an opposing area between the photosensitive member 32 and the developing roll 352. In the development region, the toner in the developer flies and is attracted to the latent image on the photosensitive member 32 by the developing bias applied between the developing roller 352 and the photosensitive member 32 and the magnetic pole distribution on the developing roller 352 side. . The developer on the developing roll 352 after development is led to the lower stirring and conveying member 354 side via the conveying member 355.

Further, the transfer device 36 is disposed opposite to the photosensitive member 32 with the recording medium 40 interposed therebetween, and a photosensitive member is formed by forming a predetermined transfer electric field between the transfer device 36 and the photosensitive member 32. The toner image on 32 is transferred onto the recording medium 40. The recording medium 40 includes not only paper but also, for example, an intermediate transfer member in an intermediate transfer type image forming apparatus.
Further, as the pre-cleaning charging device 37, for example, a charge adjustment device made of corotron or the like is used.
Furthermore, the cleaning device 38 includes two members as the cleaning member 382 in the cleaning container 381, and includes the brush roll 382a provided on the upstream side in the rotational direction of the photosensitive member 32, and the blade 382b provided on the downstream side. Cleaning efficiency is enhanced by having two. A blocking member 383 partially fixed to the cleaning container 381 is provided between the cleaning container 381 and the photosensitive member 32 at a position below the brush roll 382 a. A flexible film material made of, for example, polyurethane is used for the blocking member 383 of the present embodiment, and the fixed end is adhesively fixed to the cleaning container 381 using, for example, a double-sided tape, and the other free end is photosensitive. It is placed in contact with the body 32. The reference numeral 384 in the cleaning device 38 is a conveying member for discharging the toner cleaned and collected by the brush roll 382a or the blade 382b from the cleaning device 38 to the outside.

-Charging device-
In the present embodiment, as shown in FIGS. 2 and 3A, the charging device 33 is provided opposite to the photosensitive member 32 as the member to be charged, extends in the axial direction, and rotates to the photosensitive member 32. The charging roll 51 as a charging member for charging the toner, and the cleaning roll as a cleaning member that extends along the charging roll 51 in the axial direction and follows the contact with the charging roll 51 to rotate and clean the charging roll 51 The second contact pressure p2 of the cleaning roller 55 against the charging roller 51 when the charging roller 51 is stopped is greater than the predetermined first contact pressure p1 of the cleaning roller 55 against the charging roller 51 when the charging roller 51 is driven. The position changing mechanism 60 is provided to change the contact position of the cleaning roll 55 in the circumferential direction of the charging roll 51 so as to be smaller.

<Charge roll, cleaning roll>
In the present embodiment, the charging roll 51 has a conductive layer 53 formed around the conductive shaft 52, and the shaft 52 is rotatably supported by a bearing member (not shown). The charging roll 51 is driven to follow the rotation of the photosensitive body 32 when the photosensitive body 32 is driven. In this example, the charging roll 51 is driven to rotate when the charging roll 51 is driven. Point to the
A charging bias (not shown) is applied to the charging roll 51 to charge the photosensitive member 32 to a predetermined charging potential.
Further, the cleaning roll 55 has a sponge layer (for example, a porous elastic layer) 57 formed around the shaft 56, and as shown in FIG. 3B, the shaft 56 is rotatably supported by the bearing member 58. It is done.
Then, the cleaning roller 55 contacts the charging roller 51 and is pressed with a predetermined load, and the sponge layer 57 elastically deforms along the circumferential surface of the charging roller 51 to form a contact portion (nip portion). There is.

<Position change mechanism>
Further, in the present embodiment, as shown in FIGS. 4 (a) and 4 (b), the position variable mechanism 60 is configured to contact the first contact position PT1 where the first contact pressure p1 acts as the contact position of the cleaning roller 55. The cleaning roller 55 has a guide groove 62 guided along a predetermined movement path between the second contact position PT2 on which the second contact pressure p2 acts and the second contact position PT2, and along the guide groove 62 A guide plate 61 for supporting the cleaning roller 55 so as to be able to advance and retract between the first contact position and the second contact position, and biasing the cleaning roller 55 from the first contact position toward the second contact position And a biasing spring 63 as a biasing element.
In this example, the biasing spring 63 pulls and biases the bearing members 58 that rotatably support both ends of the cleaning roller 55 from the first contact position toward the second contact position with the biasing force Fs (see FIG. 4). It is
When the charging roller 51 is driven, the frictional force F generated at the contact portion between the charging roller 51 and the cleaning roller 55 cleans the second contact position to the first contact position against the biasing force Fs of the biasing spring 63. The roll 55 is moved.

In this example, as shown in FIG. 3A, the guide groove 62 of the guide plate 61 is a reference line connecting the centers of the charging roll 51 and the cleaning roll 55 when the charging roll 51 is not driven (corresponding to the stop). It has a shape linearly extending in a direction U inclined at a non-perpendicular angle to L.
Here, as shown in FIG. 3A and FIG. 4A, the acting direction of the frictional force F generated at the contact portion between the charging roll 51 and the cleaning roll 55 is a direction orthogonal to the reference line L, and a reference The direction orthogonal to the line L and the direction U in which the guide groove 62 extends are arranged to intersect at a crossing angle θ.

<Biting amount of cleaning roll>
The radius of the charging roll 51 (not in contact with the cleaning roll 55) is r1, and the radius of the cleaning roll 55 (not in contact with the charging roll 51) is r2, as shown in FIGS. 4 (a) and 5 (a). As shown in FIG. 4 (b) and FIG. 5 (b), the center-to-center distance between the charging roll 51 and the cleaning roll 55 at the first contact position (when the charging roll 51 is driven) is shown in FIG. Assuming that the center-to-center distance between the charging roll 51 and the cleaning roll 55 is B and r1 + r2 is C when the charging roll 51 is stopped),
A <B <r1 + r2 = C (Equation 1)
To meet.

Furthermore, assuming that the first bite amount h1 of the cleaning roller 55 at the first contact position is C-A, and the second bite amount h2 of the cleaning roller 55 at the second contact position is C-B,
h1> h2 ... (Equation 2)
To meet.
Here, considering the first bite amount h1 and the second bite amount h2 of the cleaning roller 55, the second bite amount h2 is at least when the cleaning roller 55 is driven to rotate when the charging roller 51 is driven. It is necessary to set it to more than the required driven limit bite amount. That is, as shown in FIG. 5C, the second contact pressure p2 of the cleaning roller 55 against the charging roller 51 acts on the contact portion between the charging roller 51 and the cleaning roller 55 at the second bite amount h2. Therefore, the frictional force F generated at the contact portion at this time is determined by the second contact pressure p 2 and the frictional resistance between the contact portion of the charging roll 51 and the cleaning roll 55. Therefore, by setting the second bite amount h2 to the driven limit bite amount or more, the frictional force F required for the driven rotation of the cleaning roll 55 is generated depending on this.
The first bite amount h1 may be any amount as long as it generates the first contact pressure p1 necessary for the cleaning roller 55 to exert the cleaning ability to the charging roller 51 when the charging roller 51 is driven. At this time, the cleaning ability of the cleaning roller 55 is also determined by the first contact pressure p 1 and the frictional resistance between the contact portions of the charging roller 51 and the cleaning roller 55. For this reason, as shown in FIG. 5C, the first bite amount h1 is selected so that the first contact pressure p1 in a range sufficient for securing the cleaning ability by the cleaning roller 55 can be obtained. It is necessary to.

<Selection of guide groove length>
As the length of the guide groove 62 of the guide plate 61, as shown in FIGS. 4 (a) and 4 (b) and 6 (a), the movement of the cleaning roller 55 from the first contact position to the second contact position It is necessary to allow the quantity D. Therefore, as the length of the guide groove 62, the movement amount D of the cleaning roll 55 is satisfied, and when the cleaning roll 55 satisfies the movement amount D, the first and second bite amounts h1 and h2 are obtained. The selection may be made to secure the bite amount difference Δh (h1−h2) which is the difference. In FIG. 6A, m is an arc locus having a radius of B.
Therefore, in the present embodiment, as shown in FIGS. 4A and 4B, when the cleaning roll 55 is positioned at the first contact position, the shaft 56 of the cleaning roll 55 is at one end position 62a of the guide groove 62. When the cleaning roll 55 is at the second contact position, the shaft 56 of the cleaning roll 55 is restricted to the other end position 62 b of the guide groove 62.

<Selection of biasing force by biasing spring>
Now, as shown in FIG. 6 (b), when the cleaning roller 55 moves from the second contact position to the first contact position, the biasing force Fs of the biasing spring 63 causes the cleaning roller 55 to be in the second contact position. In addition to the biasing force (Fs (B)) at the time of being positioned at (5), the biasing spring 63 is extended by the moving amount D of the cleaning roll 55, the amount is increased by Fs (D).
On the other hand, when the cleaning roller 55 is driven, the frictional force F acts on the contact portion between the charging roller 51 and the cleaning roller 55, and the frictional force F causes the cleaning roller 55 to move from the second contact position to the first contact position. And be moved. At this time, of the frictional force F, the component opposed to the biasing force Fs of the biasing spring 63 is F · cos θ,
F · cos θ ≧ Fs = Fs (B) + Fs (D) (Equation 3)
It should be selected to satisfy the above.

-Operation of charging device-
Next, the operation of the charging device according to the present embodiment will be described.
Now, when the charging roller 51 is not driven (when stopped), as shown in FIGS. 4 (b) and 5 (b), the cleaning roller 55 is biased by the biasing spring 63 to the other of the guide groove 62 of the guide plate 61. It is located at the end position 62b. In this state, the cleaning roller 55 bites into the charging roller 51 by the second bite amount h2 at the second contact position of the charging roller 51, and is disposed in contact with the charging roller 51 at a second contact pressure p2.
Next, when the charging roller 51 is driven, as shown in FIGS. 4A and 5A, the cleaning roller 55 located at the second contact position follows the driving of the charging roller 51 so that the frictional force F is reduced. The cleaning roller 55 is pushed in a direction against the biasing force Fs of the biasing spring 63, moves along the guide groove 62 of the guide plate 61, and reaches one end position 62a of the guide groove 62. In this state, the cleaning roller 55 bites in the first contact position of the charging roller 51 by a first bite amount h1, and is disposed in contact with the charging roller 51 at a first contact pressure p1. For this reason, when the charging roll 51 is driven, the cleaning roll 55 follows and rotates, and the circumferential surface of the charging roll 51 is cleaned.

形態 Form of comparison 1
FIGS. 7 (a) and 7 (b) show the main parts of the charging device according to the first comparison example.
In the figure, the charging device 33 'has the charging roller 51 and the cleaning roller 55 substantially similar to those of the first embodiment, but has a position variable mechanism 60' different from that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the detailed description thereof is omitted here.
In this example, the position change mechanism 60 'has a guide groove 62' of the guide plate 61 'extending at an angle substantially perpendicular to the reference line L connecting the centers of the charging roll 51 and the cleaning roll 55, and the first contact position In this embodiment, the cleaning roller 55 is biased by the biasing spring 63 'from PT1 toward the second contact position PT2.
In this example, when the movement amount D between the first contact position and the second contact position of the cleaning roll 55 is small, the two rolls 51 and 55 at the first contact position and the second contact position are used. Since the center-to-center distances A and B are A 食 い B, the bite amount of 1 required for the cleaning ability by the cleaning roller 55 at the first contact position is almost the same as the second bite amount. It is difficult to secure the ability. Furthermore, when the moving amount D of the cleaning roller 55 is relatively large, the relationship of A <B is established, and the frictional force F at the contact portion between the charging roller 51 and the cleaning roller 55 is weakened, There is a concern that it will become more difficult to secure the cleaning ability by the cleaning roll 55.

Second Embodiment
8 (a) and 8 (b) show the main part of the charging device according to the second embodiment.
In the figure, the basic configuration of the charging device 33 is substantially the same as that of the first embodiment, but has a position variable mechanism 60 different from that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted here. The same applies to the following embodiments and modifications.
In the present embodiment, the position variable mechanism 60 includes the guide plate 61, the guide groove 62 and the biasing spring 63 substantially similar to those of the first embodiment. However, unlike the first embodiment, the length of the guide groove 62 is different. Assuming that the height is D1, the movement amount D of the cleaning roller 55 between the first contact position PT1 and the second contact position PT2 in the first embodiment is set larger.
Therefore, in the present embodiment, when the charging roller 51 is driven, as shown in FIGS. 8A and 8B, the cleaning roller 55 positioned at the second contact position follows the driving of the charging roller 51. The frictional force F acts, the cleaning roller 55 is pushed in the direction against the biasing force Fs of the biasing spring 63, and moves along the guide groove 62 of the guide plate 61, but one end position 62a of the guide groove 62 And remain in the middle of the guide groove 62. In this state, the cleaning roller 55 bites in the first contact position of the charging roller 51 by a first bite amount h1, and is disposed in contact with the charging roller 51 at a first contact pressure p1. For this reason, when the charging roll 51 is driven, the cleaning roll 55 follows and rotates, and the circumferential surface of the charging roll 51 is cleaned. At this time, the cleaning roller 55 is disposed at a position where the above-described frictional force F and the biasing force Fs of the biasing spring 63 are balanced, and is not restricted to one end position 62 a of the guide groove 62. Even if the hardness of the cleaning roll 55 varies or changes with time, it is possible to bring the cleaning roll 55 into contact with the charging roll 51 with a constant load at the first contact position PT1.

Third Embodiment
9 (a) and 9 (b) show the main part of the charging device according to the third embodiment.
In the figure, the basic configuration of the charging device 33 includes the charging roller 51 and the cleaning roller 55 as in the first and second embodiments, but includes the position variable mechanism 60 different from the first and second embodiments. ing.
In the present embodiment, the cleaning roll 55 is disposed to the side of the charging roll 51, and the position variable mechanism 60 forms the guide groove 62 of the guide plate 61 in the substantially vertical direction, and the second contact position By arranging PT 2 to be located below first contact position PT 1, gravity Fg is applied to cleaning roll 55 without using biasing spring 63 used in the first and second embodiments. It is intended to be used as a power.
According to the present embodiment, when the charging roller 51 is driven, the cleaning roller 55 positioned at the second contact position follows the driving of the charging roller 51 as shown in FIGS. The force F acts and the cleaning roll 55 is pushed in the direction against the gravity force Fg, and moves along the guide groove 62 of the guide plate 61 to reach one end position 62 a of the guide groove 62. In the state, the cleaning roller 55 bites into the charging roller 51 by the first bite amount h1 at the first contact position of the charging roller 51, and is disposed in contact with the charging roller 51 at the first contact pressure p1. For this reason, when the charging roll 51 is driven, the cleaning roll 55 follows and rotates, and the circumferential surface of the charging roll 51 is cleaned.

The present invention is not limited to the charging device 33 according to the first to third embodiments described above, and may be configured as, for example, the charging device according to first and second modified embodiments shown in FIGS. It does not matter.
形態 Modification 1
The charging device 33 according to the first modification is configured substantially the same as the first embodiment as shown in FIG. 10A, but has a position variable mechanism 60 different from the first embodiment. .
In this example, the position variable mechanism 60 includes the guide plate 61, the guide groove 62, and the biasing spring 63 in substantially the same manner as in the first embodiment. However, unlike the first embodiment, the middle portion of the guide groove 62 62c is configured as a curved shape instead of a linear shape.
Even in the present example, if, for example, both end positions 62a and 62b of the guide groove 62 are set as the first contact position PT1 and the second contact position PT2 of the cleaning roll 55, an intermediate portion of the guide groove 62. Even if the curved portion 62c is present, there is no particular problem if the guiding property of the cleaning roll 55 is not impaired.
形態 Modification 2
The charging device 33 according to the second modification is configured substantially the same as the first embodiment as shown in FIG. 10B, but unlike the first embodiment, the guide groove 62 of the position variable mechanism 60 is different. The attached guide plate 61 and the bearing member 80 of the charging roll 51 are integrally formed as a bearing position regulating part 100.
Even in this example, the charging device 33 has substantially the same function as that of the first embodiment.

Example 1
In this embodiment, the charging device according to the first embodiment is embodied, and the bite amount at the time of driving is set when the charging roller 51 is not driven (at the time of stop).
In the present example, the charging roller 51 and the cleaning roller 55 have the following specifications.
● Charge roll 51:
· Outer diameter φ12
・ Hardness Asuka C 70 °
・ Surface roughness (Rz) 5μm
・ 340 mm in total length
● Cleaning roll 55:
· Configuration Foamed urethane spiral · Outer diameter φ 10.6
・ Hardness 300N (raw hardness)
・ Density 70kgf / m ³
・ Total length 347 mm

In this example, the relationship between the bite amount and the evaluation grade (contaminated muscle G) on the contaminating streaks (lines generated due to poor cleaning by the cleaning roll) and the evaluation grade on the storage streaks (lines generated due to the depression of the charging roll) The result shown in FIG. 11 was obtained.
In the figure, the driven limit biting amount is 0.1 mm, and in consideration of the outer diameter tolerance and the hardness tolerance of both rolls, if the biting amount tolerance is ± 0.35 mm, the target of the biting amount at the time of driving is Assuming that the value is 0.6 mm and the target value of the bite amount at the time of stop is 0.5 mm, the bite amount that can be selected is selected as follows.
Amount of biting during driving: 0.6 ± 0.35 mm
Biting amount at stop: 0.5 ± 0.35 mm

  DESCRIPTION OF SYMBOLS 1 ... charging member, 2 ... cleaning member, 3 ... position variable mechanism, 4 ... guiding member, 5 ... guiding groove, 6 ... energizing element, 11 ... charged body, 12 ... charging device, A ... first contact position Center-to-center distance between the charging member and the cleaning member in PT1, B: center-to-center distance between the charging member and the cleaning member at the second contact position PT2, p1: first contact pressure, p2: second contact pressure, h1 ... 1st bite amount, h 2 ... 2nd bite amount

Claims (12)

A charging member provided opposite to the member to be charged, extending in the axial direction, and rotating to charge the member to be charged;
A cleaning member which extends axially along the charging member and which follows and contacts the charging member to rotate and clean the charging member;
The second contact pressure of the cleaning member against the charging member when the charging member is stopped is smaller than the predetermined first contact pressure of the cleaning member against the charging member when the charging member is driven. A position changing mechanism for changing the contact position of the cleaning member with respect to the circumferential direction of the charging member;
In the position changing mechanism, the cleaning member is disposed between a first contact position where the first contact pressure acts as a contact position of the cleaning member and a second contact position where the second contact pressure acts. It has a guide groove guided along a predetermined movement locus, and supports the cleaning member so as to be able to advance and retract along the guide groove between the first contact position and the second contact position. A guide member,
And a biasing element for biasing the cleaning member from the first contact position toward the second contact position,
The cleaning member is moved from the second contact position to the first contact position against the biasing force of the biasing element by the frictional force generated at the contact portion between the charging member and the cleaning member when the charging member is driven. A charging device characterized by moving a In the charging device according to claim 1,
The radius of the charging member (not in contact with the cleaning member) is r1, the radius of the cleaning member (not in contact with the charging member) is r2, and the distance between the center of the charging member and the cleaning member at the first contact position is Assuming that A, a center-to-center distance between the charging member and the cleaning member at the second contact position is B, and r1 + r2 is C,
A charging device characterized by satisfying A <B <r1 + r2 = C. In the charging device according to claim 2,
Assuming that the first bite amount h1 of the cleaning member at the first contact position is C-A, and the second bite amount h2 of the cleaning member at the second contact position is C-B,
A charging device characterized by satisfying h1> h2. In the charging device according to claim 3,
Assuming that the moving amount of the cleaning member from the first contact position to the second contact position is D, at least a biting amount difference Δh (= h1−h2) between the two is selected to be secured. Charging device. In the charging device according to claim 3,
The second bite amount h2 of the cleaning member at the second contact position is set to at least a follower limit bite amount necessary for the cleaning member to be driven to rotate at the time of driving the charging member. Charging device. In the charging device according to any one of claims 1 to 5,
The charging device according to claim 1, wherein the guide member has a linear guide groove inclined at a non-perpendicular angle to a reference line connecting the centers of the charging member and the cleaning member when the charging member is stopped. In the charging device according to claim 6,
A charging device characterized in that the guide groove allows the movement amount D of the cleaning member, where D is the movement amount of the cleaning member from the first contact position to the second contact position. In the charging device according to claim 7,
3. The charging device according to claim 1, wherein one of the end positions of the guide groove regulates the first contact position or the second contact position of the cleaning member. In the charging device according to claim 7,
3. The charging device according to claim 1, wherein the guide groove has a first position where the cleaning member contacts the cleaning member at a position halfway to one end position. In the charging device according to any one of claims 1 to 9,
The biasing element utilizes the gravity as a biasing force by forming the guide groove in a substantially vertical direction and arranging the second contact position to be positioned lower than the first contact position. A charging device characterized by The charging device according to any one of claims 1 to 10.
The charging device according to claim 1, wherein the guide member doubles as a bearing member of the cleaning member. A chargeable object,
And a charging device for charging the body to be charged.
The charging device is provided opposite to the member to be charged, extends in the axial direction, and rotates to charge the member to be charged.
A cleaning member which extends axially along the charging member and which follows and contacts the charging member to rotate and clean the charging member;
The second contact pressure of the cleaning member against the charging member when the charging member is stopped is smaller than the predetermined first contact pressure of the cleaning member against the charging member when the charging member is driven. A position changing mechanism for changing the contact position of the cleaning member with respect to the circumferential direction of the charging member;
In the position changing mechanism, the cleaning member is disposed between a first contact position where the first contact pressure acts as a contact position of the cleaning member and a second contact position where the second contact pressure acts. It has a guide groove guided along a predetermined movement locus, and supports the cleaning member so as to be able to advance and retract along the guide groove between the first contact position and the second contact position. A guide member,
And a biasing element for biasing the cleaning member from the first contact position toward the second contact position,
The cleaning member is moved from the second contact position to the first contact position against the biasing force of the biasing element by the frictional force generated at the contact portion between the charging member and the cleaning member when the charging member is driven. An image forming apparatus characterized by moving

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