JP3835588B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, an image transferred from a photosensitive member to an intermediate transfer member is transferred to a recording medium that is nipped between the intermediate transfer member and a transfer device facing the intermediate transfer member when the electric field is formed by the transfer device. An image forming apparatus for transferring, in particular, a discharge unit that forms a reverse polarity electric field with the transfer unit. The discharge unit prevents the recording medium from being caught in the intermediate transfer member, and the intermediate transfer member is easily cleaned. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
Conventionally, a fur brush system that electrically removes residual toner after transfer is well known.
In the electric suction method using the fur brush, complete cleaning is not performed unless the residual toner on the surface of the intermediate transfer member is charged in one direction.
[0003]
Therefore, for example, in order to improve the adsorption of the residual toner by the positively charged fur brush, it is necessary to negatively charge the residual toner, and an electric field opposite to the fur brush is formed on the upstream side of the fur brush. An electric field forming device will be arranged.
[0004]
An apparatus described in the full text of Japanese Utility Model Laid-Open No. 59-123872, which is one of those apparatuses, is also adjacent to the fur brush that electrically sucks the residual toner on the surface of the image carrier. A method such as providing an electric field curtain for cleaning assistance on the upstream side is used.
[0005]
[Problems to be solved by the invention]
However, this technique has a complicated structure due to the provision of the above-described electric field curtain for assisting cleaning, which increases the number of parts and increases the cost, and is contrary to miniaturization due to a layout problem.
On the other hand, the present inventors have arranged a discharge means for forming a reverse polarity electric field with a transfer device for secondary transfer of an image on the intermediate transfer member onto a recording medium, adjacent to the downstream side of the transfer device. An electric field opposite to the secondary transfer bias is applied to the recording medium after transfer to the intermediate transfer body, and an electric charge repelling the intermediate transfer body is applied to the recording medium to prevent the recording medium from being caught in the intermediate transfer body. An image forming apparatus is being developed.
[0006]
The inventors have found that the electric field forming device that forms an electric field opposite to the above-described fur brush and the discharging means share the cost problem as well as the layout problem. is there.
[0007]
The present invention has been made in view of the above problems, and after the secondary transfer is performed from the intermediate transfer member to the recording medium, a discharging unit that applies a reverse voltage to the portion to prevent adsorption to the intermediate transfer member. When the recording medium is not conveyed to the intermediate transfer body, an object of the present invention is to provide an image forming apparatus that applies the reverse voltage to the residual toner on the surface of the intermediate transfer body by the discharge means.
[0008]
Another object of the present invention is to provide an image forming apparatus capable of easily cleaning the surface of the intermediate transfer member when the recording medium is not conveyed to the intermediate transfer member.
[0009]
[Means for Solving the Problems]
In the present invention, an image transferred from a photosensitive member to an intermediate transfer member is transferred to a recording medium that is nipped between the intermediate transfer member and a transfer device facing the intermediate transfer member when the electric field is formed by the transfer device. In the image forming apparatus to transfer,
It is possible to move between a transfer position where the recording medium is pressed toward the intermediate transfer body and the image is transferred from the intermediate transfer body to the recording medium, and an initial position where the image is separated from the intermediate transfer body and retracted from the transfer position. The transfer device;
Discharging means disposed adjacent to the downstream side of the transfer device and facing the intermediate transfer body, and forming a reverse polarity electric field with the transfer device;
A cleaning unit disposed on the downstream side of the discharge unit and cleaning the residual toner on the surface of the intermediate transfer member by an electric suction force;
At the time of transfer of the recording medium, the discharging means discharges the recording medium transferred by the transfer device so as to be separated from the intermediate transfer body after transfer, and between the discharging means and the intermediate transfer body. In the case where the recording medium does not exist, the residual toner on the surface of the intermediate transfer member is charged so as to be sucked by the cleaning unit,
After the transfer unit is retracted to the initial position and the recording medium is not present between the discharge unit and the intermediate transfer member, residual toner on the surface of the intermediate transfer member is charged by the discharge unit. The residual toner is cleaned by the cleaning means.
[0010]
According to this technical means, the discharge means is disposed adjacent to the downstream side of the transfer device for applying a voltage for secondary transfer of the image to the recording medium so as to face the intermediate transfer member, and the transfer device provides the transfer device. And a magnetic field having a polarity opposite to that of the recording medium transferred by the transfer unit is imparted to the intermediate transfer member, so that the recording medium is attracted to the intermediate transfer member. Can be prevented.
[0011]
In addition, since the discharge unit and a cleaning unit that is disposed downstream of the discharge unit and sucks and cleans the residual toner on the surface of the intermediate transfer body by an electric suction force, the transfer unit includes the initial unit. In the state where the recording medium is retracted to the position and the recording medium is not present between the discharge means and the intermediate transfer body, that is, when the secondary transfer state from the intermediate transfer body to the recording medium is not established, the discharge After the residual toner on the surface of the intermediate transfer member is charged by the means, the residual toner can be cleaned by the cleaning means, so that the residual toner can be removed satisfactorily.
[0013]
According to such technical means, when transferring the recording medium, the image of the intermediate transfer member is transferred by the transfer device, but the transferred portion of the recording medium is discharged by the discharging means so as to be separated from the intermediate transfer member. For this reason, the separation habit is imparted to the transfer portion of the recording medium in the direction opposite to the direction of attracting to the intermediate transfer member, so that the attracting to the intermediate transfer member is prevented.
[0014]
In addition to the separation behavior, the discharging means sucks residual toner on the surface of the intermediate transfer body by the cleaning means when there is no recording medium between the discharging means and the intermediate transfer body. Charge. Therefore, it is possible to satisfactorily clean the residual toner on the intermediate transfer member.
According to such technical means, the above-described separation property with respect to the recording medium and charging of the residual toner can be performed by one discharging means, and the number of members is reduced and the configuration is simplified.
[0015]
It is also an effective means of the present invention that the cleaning means performs the cleaning operation at the time of start-up or after image transfer to the final recording medium. According to such a technique, since the surface of the intermediate transfer member is first cleaned at the time of starting the image forming operation, good transfer is performed. Regardless of the non-continuous print mode or the continuous print mode, the surface of the intermediate transfer member is cleaned after the image is transferred to the final recording medium, so that a good transfer is performed during image formation.
[0016]
It is also an effective means of the present invention that the cleaning means performs a cleaning operation when the recording medium is restored after jam processing.
According to such a technique, when the recording medium adsorbed on the intermediate transfer member is detected by the detecting means, the recording medium is automatically conveyed by the registration roller pair, but the jammed recording medium is opened by opening the jam processing opening / closing device. After being taken out of the apparatus, the intermediate transfer member can be cleaned to return to the image formable state in conjunction with the closing operation of the opening / closing device or by the switch operation of the jam handler.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
[0018]
FIG. 1 is a cross-sectional view of a main part of an image forming apparatus according to an embodiment of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The photosensitive drum 1 is made of amorphous silicon, and includes four developing devices including a charger (charging roller) 3, an optical scanning unit 2, and a developer container around the photosensitive drum 1 in the rotation direction. 4Y (for yellow), 4M (for magenta), 4C (for cyan), 4K (for black), a first static eliminator 13, an intermediate transfer member 5, a cleaning device 6, and a second static eliminator 4 are provided. .
[0019]
The intermediate transfer member 5 has a volume resistivity in the thickness 50~200μm is, 10 ⁹ Ω · cm~10 an intermediate transfer film ¹² Omega · cm, the intermediate transfer member 5 is appropriate nip between the photosensitive drum 1 ( The outer periphery contacts with a width of about 10 mm, and both are configured to be rotatable in the direction of the arrow through a reduction gear train by a main motor (not shown).
[0020]
Around the intermediate transfer member 5, a curl correcting means 7, a transfer roller 9, a separation discharger 10, and an intermediate transfer member 5, which constitute a decurling mechanism with a pair of registration rollers 7 a and 7 b from the upstream side in the conveyance direction of the recording medium 8. Jam detection means (detection means) 11 for detecting the leading end of the attached recording medium and detecting that the recording medium has jammed, and a fur brush cleaner 12 for removing residual toner on the intermediate transfer member 5 are provided. The recording medium 8 is configured to be transportable along a transport path 14 to a fixing device (not shown).
[0021]
The curl correcting means 7 includes an elastic roller 7a having a sponge layer formed on a rigid core shaft, and a rigid roller 7b having a smaller diameter than the elastic roller 7a, and presses the recording medium 8 at a linear pressure of 0.2 kg / cm. As a result, plastic deformation of the recording medium occurs, and curl correction can be performed so as to be convex toward the intermediate transfer member.
[0022]
The transfer roller 9 has a volume resistivity of 10 ⁷ Ω · cm to 10 ⁹ Ω · cm and an elastic body thickness of 5 to 10 mm, and is usually retracted to an initial position separated from the outer periphery of the intermediate transfer body 5. However, before the registration roller pair 7a, 7b conveys the recording medium 8, the outer periphery of the intermediate transfer body 5 is pressed and contacted, and a predetermined voltage is applied to the surface opposite to the transfer surface of the recording medium 8 to perform recording. As described later, when the transfer of the image onto the medium is completed or even before the transfer is completed, the initial position can be returned.
[0023]
The separation discharger (discharge means) 10 is arranged downstream of the transfer roller 9 and electrically neutralizes the transfer roller 9 by, for example, positively charging the negatively charged recording medium 8. It is. As a result, the electrostatic attractive force acting on the transfer portions of the intermediate transfer body 5 and the recording medium 8 can be suppressed.
[0024]
Further, the separation discharger 10 charges the residual toner on the intermediate transfer member 5 to have the same polarity when the recording medium 8 is not present between the separation discharger 10 and the intermediate transfer member 5. A discharge that assists the electrical suction operation of the residual toner by the fur brush cleaner 12 is performed.
[0025]
The jam detecting means 11 is for observing the end of the central transfer body 5 in the axial direction. More specifically, the jam detection means 11 detects the recording medium 8 when the recording medium 8 adheres to the intermediate transfer body 5 and rotates. Arranged as possible.
This detection means 11 has a light emitting portion and a light receiving portion, detects a recording medium by detecting the presence or absence of reflected light based on a difference in reflectance from the surface of the intermediate transfer body, and a control not shown in the figure. It is sent to the device.
Then, when the leading edge of the recording medium adhering to the surface of the intermediate transfer member 5 is separated, it is separated from the surface of the intermediate transfer member 5 by a predetermined distance (for example, 5 mm or more) so as to be caught by the detection means 11 and not bend. It is desirable to arrange them.
[0026]
The fur brush cleaner 12 is configured to plant conductive fibers in a cylindrical body rotating in the direction of the arrow and apply a high voltage from the power source 17, and is arranged downstream of the jam detection means (detection means) 11. The cleaner is for cleaning the surface of the intermediate transfer member by electrically sucking in the residual toner on the intermediate transfer member by the rotation of the brush to which the voltage is applied. The toner adhering to the brush is attracted by applying a voltage to the metal recovery roller, and then the recovery roller is cleaned with a blade and discharged to the outside by a screw.
[0027]
Since the present embodiment is configured as described above, at the time of printing, the photosensitive drum 1 is charged by the charger 3 for each color in the order of the developing units 4K, 4C, 4M, and 4Y. The images developed by the exposure and developing devices 4K, 4C, 4M, and 4Y are transferred to the intermediate transfer member 5, transferred to a recording medium 8 conveyed from a paper feeding cassette (not shown) by a transfer roller 9, and then fixed by a fixing device (not shown). Heat and press to fix and discharge.
[0028]
Next, the operation in the jam state in which the recording medium 8 is attracted to the surface of the intermediate transfer member 5 will be described in detail with reference to FIGS.
In FIG. 1, when a start switch on an operation panel provided on an apparatus main body (not shown) is pressed, a main motor (not shown) rotates, the photosensitive drum 1 and the intermediate transfer body 5 start to rotate, and the discharging means 10 discharges to the intermediate position. The residual toner on the surface of the transfer body 5 is neutralized, and the fur brush cleaner 12 is driven to electrically suck the residual toner on the surface of the intermediate transfer body.
[0029]
A primary transfer position T which is a contact point between the photosensitive drum 1 and the intermediate transfer member 5 through the contact point R ₀ between the photosensitive drum 1 and the charging roller 3 in FIG. the distance D on the photoreceptor drum to the _{1 (R 0 → R 1 →} T 1), the distance _{L 3} to the position _{P 2} and the primary transfer position _{T 1} of the on the intermediate transfer member 5 of the fur brush roller 12 Is a relationship of D> L ₃ , and therefore, when the portion (auxiliary charging portion) where the discharging means 10 discharges and the residual toner on the surface of the intermediate transfer member 5 is charged reaches the point P ₂ , the charging roller 3 When the photosensitive drum 1 starts charging by, around the toner image developing device 4K of the first color is developed reaches the primary transfer position T _1, the auxiliary charging unit is already cleaned by the fur brush cleaner 12, in a position beyond the first transfer position T _1, subsequent first Eye toner image developed by the developer 4K becomes possible to face the cleaned intermediate transfer member surface, the residual toner, dust, will not involve the photosensitive drum surface and the like dust.
[0030]
The photosensitive drum 1 shown in FIG. 1 is developed from the developing unit 4K through 4C and 4M for each rotation, and 4Y is developed, sequentially transferred onto the intermediate transfer member, and formed on the surface of the intermediate transfer member 5. multicolor toner image, by the rotation of the intermediate transfer member 5 approaches the second transfer position T _2, the registration roller pair 7a, 7b is the tip of the multi-color toner image approaches the second transfer position T ₂ The transfer roller 9 presses the surface of the intermediate transfer member 5 in synchronism with the recording medium 8.
[0031]
The transfer roller 9 applies a negative transfer voltage from the back surface of the recording medium 8 to secondarily transfer the multicolor toner image to the recording medium 8.
The multi-color toner image is neutralized electrically by discharging positive charges by a separation discharger 10 arranged downstream of the transfer roller 9. As a result, the electrostatic attractive force acting on the transfer portions of the intermediate transfer body 5 and the recording medium 8 can be suppressed.
Thereafter, the recording medium 8 is moved to the left in FIG. 1, and the image is fixed by a fixing device (not shown).
[0032]
In FIG. 2, when the recording medium 8 secondarily transferred by the transfer roller 9 is conveyed while adsorbed on the surface of the intermediate transfer body 5, it is detected by the detecting means 11 (20), and the transfer roller 9 is transferred to the transfer voltage. Is stopped (21), and the pressure on the recording medium 8 is released to return to the initial position.
[0033]
To the recording medium 8 by the transfer roller 9, from the position to Q ₁ downstream end thereof a position substantially pressed by substantially transfer roller 9 of the separation discharger 10, a recording medium was negatively charged 8 where to positively charged transfer portion and _{Q 2,} the conveying speed of the recording medium is taken as V, and when the elapsed t1 = distance _(Q 1 _~Q 2) / V time (22), separated Discharge is stopped (23).
[0034]
Thus, a positive charge is discharged to the transfer portion of the recording medium 8 that is negatively charged to electrically neutralize the electrostatic transfer force that acts on the transfer portion of the intermediate transfer body 5 and the recording medium 8. it can.
[0035]
If the rotation of the registration rollers 7a and 7b is stopped and the conveyance of the recording medium 8 is stopped with the intermediate transfer body 5 and the photosensitive drum 1 being rotated (24), the recording medium 8 is overrun. , the tip and the center point P ₂ of the cleaning means 12 as indicated as S _1, and stops positioned between the viewing point P ₁ of the detection means 11.
[0036]
Thereafter, the toner image on the surface of the intermediate transfer member is removed by the cleaning means, and the intermediate transfer member is rotated by a predetermined amount.
In the present embodiment, t2 = (L ₀ + L) where V is the conveyance speed of the recording medium, L ₀ is the circumferential length of the intermediate transfer member, and L ₂ is the distance between the detection unit 11 and the cleaning unit 12. ₂ ) When the time of / V has elapsed (25), the operation of the cleaning means 12 is stopped (26).
[0037]
On the other hand, when the recording medium 8 is conveyed while adsorbed to the surface of the intermediate transfer member 5 and detected by the detection means 11 (20), charging of the photosensitive drum 1 is stopped (32).
After the charging bias voltage of the charger is stopped, until the charged portion of the photosensitive member finishes development, that is, the recording medium conveyance speed is V, and the position from the charging position to the fourth developing device 4Y is set. When the distance up to M is M, when t4 = M / V has elapsed (33), development is stopped (34).
[0038]
After the charging bias voltage of the charger is stopped, the rotation of the photosensitive member is continued until the charged portion of the photosensitive member finishes developing to stop the developing operation of the developing device, and the rotational driving of the photosensitive member is stopped. Thus, the carrier does not fly to the non-charged portion of the photoreceptor.
[0039]
When the cleaning means 12 is stopped and the intermediate transfer member and the photosensitive drum are stopped (27) by stopping the main motor, as a result, the recording medium 8 is separated from the surface of the intermediate transfer member 5, and one point in FIG. The recording medium is placed on the transport path 14 via the two-dot chain line from the chain line, and the recording medium is transported again (28).
[0040]
The conveying speed of the recording medium V, L the length of the one printing medium, the registration roller pair 7a, the length of the conveying path to 7b and the detection means 11 When _{L 1, t4 = (L-} L ₁ ) After conveying by / V (29), the conveyance of the recording medium 8 by the registration roller pair 7a, 7b is stopped (30), so that the rear end of the recording medium 8 is separated from the registration roller pair 7a, 7b, 3 points It is transported and placed like a chain line.
Further, even if the recording medium is adsorbed on the surface of the intermediate transfer member, the adsorbing force becomes weak, and by re-transporting the recording medium, the recording medium is separated from the surface of the intermediate transfer member, and from the one-dot chain line in FIG. It is transported and placed on the transport path 14 via a two-dot chain line as a three-dot chain line.
[0041]
Then, after the adsorbed portion of the recording medium adsorbed on the intermediate transfer member is peeled off from the intermediate transfer member, the curl correcting means removes the recording medium until the recording medium is removed from the curl correcting means (registration roller pair 7a, 7b). Since the recording medium is conveyed, the recording medium stops before the leading edge reaches the fixing device, and there is nothing to hold down the recording medium 8 in that state. Therefore, the operator opens the cover of the apparatus main body, as shown in FIG. The recording medium 8 can be easily taken out of the apparatus in a state where the portion from the curl correcting means (7a, 7b) to the conveyance path 14 is exposed, and jammed paper processing (31) can be performed.
[0042]
After the jam processing, when the operator closes the cover of the apparatus main body, the main motor (not shown) rotates in conjunction with a switch (not shown), the photosensitive drum 1 and the intermediate transfer body 5 start to rotate, and the discharging means 10 discharges. Then, the residual toner on the surface of the intermediate transfer member 5 is charged, and the fur brush cleaner 12 is driven to electrically suck the residual toner on the surface of the intermediate transfer member.
[0043]
Further, in the present embodiment, the fur brush cleaning operation other than during the jam processing has been described at the time of starting the apparatus main body, but instead of at the time of starting, regardless of the non-continuous print mode or the continuous print mode, The surface of the intermediate transfer member may be cleaned after the image is transferred to the final recording medium. According to such a technique, after the image forming operation of the apparatus main body is completed, the intermediate transfer member is held in a cleaned state, so that good transfer is performed at the next image formation.
[0044]
In the present embodiment, discharge means is disposed adjacent to the intermediate transfer body adjacent to the downstream side of a transfer device for applying a voltage for secondary transfer of an image to a recording medium, and the transfer device provides the transfer device. And a magnetic field having a polarity opposite to that of the recording medium transferred by the transfer unit is imparted to the intermediate transfer member, so that the recording medium is attracted to the intermediate transfer member. Can be prevented.
[0045]
In addition, since the discharge unit and a cleaning unit that is disposed downstream of the discharge unit and sucks and cleans the residual toner on the surface of the intermediate transfer body by an electric suction force, the transfer unit includes the initial unit. In the state where the recording medium is retracted to the position and the recording medium is not present between the discharge means and the intermediate transfer body, that is, when the secondary transfer state from the intermediate transfer body to the recording medium is not established, the discharge After the residual toner on the surface of the intermediate transfer member is charged by the means, the residual toner can be cleaned by the cleaning means, so that the residual toner can be removed satisfactorily.
[0046]
In addition, the present embodiment has a discharge means, and the discharge means has a surface of the intermediate transfer member when there is no recording medium between the discharge means and the intermediate transfer member in addition to the above-mentioned separation behavior. The residual toner is charged so as to be sucked by the cleaning means. Therefore, it is possible to satisfactorily clean the residual toner on the intermediate transfer member.
Therefore, the above-described separation property with respect to the recording medium and the charging with respect to the residual toner can be performed by one discharge means, and the number of members is small and the configuration is simplified.
[0047]
【The invention's effect】
As described above in detail, the present invention has a discharge means, and the discharge means is provided between the discharge means and the intermediate transfer member in addition to the separation habit to prevent the recording medium from adsorbing to the intermediate transfer member. When there is no recording medium, the residual toner on the surface of the intermediate transfer member is charged so as to be sucked by the cleaning means, so that the residual toner on the intermediate transfer member can be satisfactorily cleaned.
Then, the above-described separation property with respect to the recording medium and the charging with respect to the residual toner can be performed by one discharge means, and the number of members is small and the configuration is simplified.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an entire image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating jam detection of a recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 5 Intermediate transfer body 7 Conveyance direction correction means (registration roller pair 7a, 7b)
9 Transfer device (transfer roller)
10 Separation discharge means 11 Jam detection means

Claims (3)

Image formation in which an image transferred from a photosensitive member to an intermediate transfer member is re-transferred to a recording medium that conveys the intermediate transfer member in a state of being sandwiched by the intermediate transfer member and the intermediate transfer member when an electric field is formed by the transfer device In the device
It is possible to move between a transfer position where the recording medium is pressed toward the intermediate transfer body and the image is transferred from the intermediate transfer body to the recording medium, and an initial position where the image is separated from the intermediate transfer body and retracted from the transfer position. The transfer device;
Discharging means disposed adjacent to the downstream side of the transfer device and facing the intermediate transfer body, and forming a reverse polarity electric field with the transfer device;
A cleaning unit disposed on the downstream side of the discharge unit and cleaning the residual toner on the surface of the intermediate transfer member by an electric suction force;
At the time of transfer of the recording medium, the discharging means discharges the recording medium transferred by the transfer device so as to be separated from the intermediate transfer body after transfer, and between the discharging means and the intermediate transfer body. In the case where the recording medium does not exist, the residual toner on the surface of the intermediate transfer member is charged so as to be sucked by the cleaning unit,
After the transfer unit is retracted to the initial position and the recording medium is not present between the discharge unit and the intermediate transfer member, residual toner on the surface of the intermediate transfer member is charged by the discharge unit. The image forming apparatus, wherein the residual toner is cleaned by the cleaning unit. Start or image forming apparatus according to claim 1, wherein the cleaning operation in the cleaning means after the image transferred to the final recording medium is performed.   The image forming apparatus according to claim 1, wherein the cleaning unit performs a cleaning operation when the recording medium is returned after jamming.

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