JP2000162894A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent scratches on the surface of a photoreceptor drum, toner fusion onto the surface of the photoreceptor drum, unusual noises, abnormal vibration, curling up of a blade, etc., and to keep the cleaning of the photoreceptor drum stable over a long period of time. SOLUTION: Secondary-transfer residual toner on an intermediate transfer body 2 is re-electrified by a solid roller 41, and recovered by a brush roller 42. After recovery is carried out a specific number of times, the recovered toner is re-electrified by the solid roller 41, and discharged onto the intermediate transfer body 2 from the brush roller 42. The discharged residual toner is transferred onto a photoreceptor drum 1 via a primary-transfer nip N1, is supplied to the cleaning blade 81 of a cleaner 8, and acts as a lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer.

[0002]

2. Description of the Related Art In image forming apparatuses such as copiers and laser beam printers, the need for color is increasing. As a color image forming method, a sublimation type, a thermal transfer type, an ink jet method, an electrophotographic method, and the like are known, and the electrophotographic method is said to be the most excellent in terms of image forming speed.

[0003] In recent years, the intermediate transfer system has become the mainstream among the electrophotographic systems. This method has advantages such as not selecting a transfer material and being excellent in color registration (less color shift).

FIG. 1 shows a schematic configuration of an image forming apparatus using a drum type intermediate transfer member. In the image forming apparatus shown in FIG. 1, a single-color toner image of yellow, magenta, cyan, and black formed on a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 is sequentially transferred to an intermediate transfer member 2. The toner images of the four colors are collectively transferred onto the transfer material in a batch.

[0005] In this method, it is not necessary to wind the transfer material P around the intermediate transfer body 2, so that it can be used for envelopes and thick paper, and has high versatility, and the color registration changes depending on the thickness of the transfer material. There is no merit that high image quality can be obtained.

In the intermediate transfer system, the intermediate transfer body 2 is
The toner (secondary transfer residual toner) remaining on the surface of the intermediate transfer body 2 without being transferred onto the transfer material P is a cleaning member, for example, a cleaning blade made of polyurethane elastomer, a fur brush made of rayon, or a winding cleaning web. And is prepared for the next image formation.

As another cleaning method, the charging means 4 which is arranged in contact with the surface of the intermediate transfer member 2 and charges the secondary transfer residual toner changes the tribo of the transfer residual toner, thereby performing primary transfer of the next image. At the same time, a technique for electrostatically collecting the secondary transfer residual toner on the photosensitive drum 1 has been developed.

More specifically, using a solid roller (charging member) 41 or a brush roller (collection member) 42 as a means for recharging the secondary transfer residual toner, a tribo of the transfer residual toner is charged in a developing unit. The toner is charged to the opposite polarity of the toner tribo, and the primary transfer of the toner image from the photosensitive drum 1 to the intermediate transfer body 2 is performed simultaneously with the transfer of the toner image from the intermediate transfer body 2 to the photosensitive drum 1.
The transfer residual toner is transferred and collectively collected by a cleaning unit (cleaning device) 8 of the photosensitive drum 1.

By using this method, the toner which does not contribute to the final image formation can be collectively collected. Therefore, compared with a case where a separate cleaning means is provided on the intermediate transfer member 2, a waste toner conveying means and a waste toner There is no need to provide a plurality of toner collection boxes, and there are advantages such as downsizing of the apparatus, cost reduction, and simplification of maintenance.

As a cleaning unit 8 for the photosensitive drum 1, a system using a cleaning blade 81 made of an elastic material such as rubber has been widely used. This is because it is simple and small, and is advantageous from the viewpoint of cost.

As a material of the cleaning blade 81, polyurethane rubber, which is a kind of thermoplastic elastomer, is mainly used in view of chemical resistance, abrasion resistance, moldability, mechanical strength and the like.

The mainstream of the cleaning unit 8 having the cleaning blade 81 is a method in which the cleaning blade 81 is pressed against the surface of the traveling photosensitive drum 1 from the counter direction. The mechanism of the cleaning action in this method is such that when the cleaning blade 81 is pressed against the surface of the photosensitive drum 1 with a force (5 to 40 gf / cm) necessary to remove the residual toner on the surface of the photosensitive drum 1, At the contact portion between the edge portion and the photosensitive drum 1, first, the edge portion of the cleaning blade 81 that is in close contact with the surface of the photosensitive drum 1 due to the frictional force acting on the contact portion is deformed (shear deformation) in the traveling direction of the photosensitive drum 1 (the direction of arrow R1). , Compressive deformation), and then the energy accumulated at the edge of the cleaning blade 81 due to the stress acts as a restoring force (repulsive elastic force) to return to the original state, which is considered to be due to the so-called Stick-Slip motion. . Therefore, in the cleaning unit 8 using the cleaning blade 81, in order to obtain stable cleaning performance, it is necessary to optimize the amplitude and frequency of the Stick-Slip motion. Stick-Sl
To optimize the amplitude and frequency of the ip motion, the frictional force between the edge of the cleaning blade 81 and the contact portion between the surface of the photosensitive drum 1, the shape of the cleaning blade 81, the material properties of the cleaning blade 81 (Young's modulus, Poisson's ratio, By adjusting the modulus (stress-strain curve) and the like.

[0013] However, with the long-term use of the apparatus, for example, NO _X in the surface of the photosensitive drum 1, by such as toner resin adheres the friction coefficient of the surface of the photosensitive drum 1 is up,
Of course, the frictional force between the edge of the cleaning blade 81 and the photosensitive drum 1 (contact portion) also increases. Therefore S
The energy stored in the edge portion of the cleaning blade 81 in the tick state increases, and the stick-
The Slip motion has amplitude> proper value, frequency <proper value (proper value is a range in which the cleaning action is stably performed).
When this phenomenon progresses, the cleaning blade 8
One edge portion jumps up without following the surface of the photosensitive drum 1, causing the toner to pass through, rubbing the toner on the surface of the photosensitive drum 1 (toner fusion, filming), and further causing abnormal noise (blading). Abnormal vibration (chattering) occurs, so-called blade turning in which the edge portion is reversed so as to follow the rotation direction of the photosensitive drum 1, and the edge portion of the cleaning blade 81 and the surface of the photosensitive drum 1 are damaged (the blade edge is chipped). , Photosensitive drum surface scratches).

In order to solve this problem, conventionally, an inorganic material such as graphite, boron nitride, molybdenum disulfide, tungsten disulfide, silicon dioxide or the like, Means have been taken to reduce the frictional force by applying a solid powder (lubricating material) of an organic substance such as resin, silicone resin, polyamide (nylon resin), polyacetal, polyethylene, or polyimide.

However, with the use of the apparatus, the lubricant disappears from the edge of the cleaning blade 81 and the frictional force increases again. Therefore, a drastic solution for reducing the frictional force between the edge of the cleaning blade 81 and the photosensitive drum 1 is provided. Does not. Although various devices have been devised for constantly supplying the above-described lubricant to the edge portion of the cleaning blade 81, the device configuration of the cleaning unit 8 is complicated and the cost is significantly increased, so that it has not been put to practical use. .

Further, conventionally, an OPC (organic optical semiconductor) photosensitive drum 1 composed of a surface layer using polycarbonate as a binder resin has been widely used for the photosensitive drum 1, but the above-mentioned problem has been solved. OPC
In some cases, a protective layer (OCL) in which a suitable amount (3 to 40 wt%) of Teflon resin is dispersed in a polycarbonate binder resin is provided on the surface of the photosensitive drum 1. A photosensitive drum 1 having this OCL as a surface layer is used, and strontium titanate, cerium oxide, alumina,
By adding inorganic particles such as zirconia and the like whose surface is hydrophobized and having a particle diameter of 2 μm or less, these inorganic particles are accumulated at the contact portion between the edge of the cleaning blade 81 and the photosensitive drum 1, and the OCL surface is removed. By polishing, the Teflon resin contained in the OCL is supplied to the contact portion to promote the lubrication effect.

However, in a case where an image with extremely low toner consumption is continuously copied in a large amount, the above-mentioned polishing is performed on the contact portion between the edge portion of the cleaning blade 81 and the photosensitive drum 1 as the number of copies increases. The effect of the inorganic fine particles is extremely reduced, and problems such as toner fusion, abnormal vibration, and blade turning may occur.

As a method for reducing the frictional force between the cleaning blade 81 and the photosensitive drum 1, the photosensitive drum 1
And a cleaning blade having a nylon resin layer disposed on the surface in contact with the cleaning blade (hereinafter referred to as “nylon coat blade”). When this nylon coat blade is used, the frictional force between the edge portion and the photosensitive drum 1 can be sufficiently reduced.

However, since the nylon resin does not have the property as an elastomer unlike polyurethane, the cleaning action of the residual toner by the Stick-Slip movement of the edge of the cleaning blade 81 is not seen, and the residual toner is blocked and scraped off. It is considered that such an action is performed. Therefore, in order to completely prevent the residual toner from slipping through, the pressing force of the cleaning blade against the surface of the photosensitive drum 1 is made much higher than that of the polyurethane blade (about 2 times of the polyurethane blade).
Times), and as a result, the cleaning blade 81
As a result, the life of the photosensitive drum 1 is shortened due to an increase in the amount of shaving on the surface of the photosensitive drum 1 or damage to the surface.

As another means, at a certain timing other than the time of image formation, a solid or half-tone obi image having a width close to the entire area in the main scanning direction or a width of several tens mm in the sub-scanning direction is formed on the photosensitive drum 1. Until now, a method of utilizing the polishing and lubricating effects of the toner by causing the toner that forms the obi image to reach the edge of the cleaning blade 81 without being subjected to the transfer action in the transfer area has been used widely ( Black obi sequence). In this black obi sequence, the cleaning action can be stabilized by the effect of polishing the attached matter on the surface of the photosensitive drum 1 to keep the surface of the photosensitive drum 1 constant and the effect of improving the lubricity of the edge of the cleaning blade 81.

However, in this black obi sequence, toner is consumed except during image formation, which increases running costs. Further, the amount of waste toner increases, so that it is necessary to increase the size of the waste toner container or shorten the time for replacing the container. is there.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made after the residual toner on the intermediate transfer member is returned to the image carrier (photosensitive drum) using a recharging means. In an image forming apparatus that performs batch cleaning with an image carrier cleaning device of a cleaning blade type, the image carrier surface is caused by a change in a pressing load of the cleaning blade against the image carrier surface caused by use of the image forming device. An object of the present invention is to provide an image forming apparatus capable of preventing scratches, fusion of toner on the surface of an image carrier, abnormal noise, abnormal vibration, turning over of a blade, etc., and ensuring high image quality and high quality. is there.

[0023]

According to a first aspect of the present invention, a toner image formed on a surface of an image carrier is transferred to a transfer material at a transfer nip portion. In an image forming apparatus for removing a residual toner remaining on the surface of an image carrier without being transferred to a transfer material by a cleaning device, the image forming apparatus may include: A recharging member disposed to recharge the residual toner remaining on the surface of the image carrier;
A collecting member disposed downstream of the recharging member and temporarily collecting the residual toner recharged by the recharging means.

According to a second aspect of the present invention, in the primary transfer nip portion, toner images of different colors sequentially formed on the surface of the image carrier are sequentially primary-transferred onto the intermediate transfer body. After the toner images of a plurality of colors are superimposed on the body, the toner images of the colors on the intermediate transfer body are collectively and secondarily transferred onto a transfer material at a secondary transfer nip portion, and at the time of the primary transfer. Residual toner remaining on the surface of the image carrier without being transferred to the intermediate transfer member and remaining toner remaining on the surface of the intermediate transfer member without being transferred onto the transfer material during the secondary transfer, and being transferred onto the image carrier. Recharging means disposed between the secondary transfer nip portion and the primary transfer nip portion along a moving direction of the surface of the intermediate transfer member in an image forming apparatus for removing residual toner by a cleaning device. The recharging means A recharging member for recharging residual toner remaining on the surface of the intermediate transfer member without being transferred to the transfer material during the secondary transfer, and a recharging member disposed downstream of the recharging member and recharged by the recharging means. And a recovery member for temporarily recovering the residual toner thus obtained.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the above image forming apparatus, the residual toner temporarily collected by the collecting member is discharged from the circulating member to a collecting source at regular intervals.

According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, the residual toner discharged from the recovery member is removed by the cleaning device.

According to a fifth aspect of the present invention, in the image forming apparatus of the first to fourth aspects, the collection member does not collect the residual toner during a density control sequence or abnormal operation of the image forming apparatus. , Characterized in that.

According to a sixth aspect of the present invention, in the image forming apparatus of the first to fifth aspects, the recharging member has a volume resistance of 10%.
It is an elastic roller of ⁵ to 10 ¹³ Ω.

According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, the recharging member is a multilayered elastic roller having at least a resistive layer and a surface release layer. I do.

The present invention according to claim 8 is directed to claim 6 or 7.
In the image forming apparatus, the recharging member may have a total pressure of 100 to 300 g with respect to the image carrier or the intermediate transfer member.
Abut on each other.

According to a ninth aspect of the present invention, in the image forming apparatus of the sixth to eighth aspects, the recharging member rotates in a counter direction with respect to a rotation direction of the image carrier or the intermediate transfer body. , Characterized in that.

The present invention according to claim 10 is the invention according to claims 1 to 9
In the above image forming apparatus, the collection member is a conductive brush.

[0033] According to an eleventh aspect of the present invention, in the image forming apparatus of the tenth aspect, the recovery member has a roller shape.

According to a twelfth aspect of the present invention, in the image forming apparatus of the tenth or eleventh aspect, the collection member has a fineness of a pile material of 100 to 500 per 100 filaments.
Denier, fiber density 100-300KF / inch
² , and penetrates into the image carrier or the intermediate transfer body with a penetration amount of 0.5 ± 0.3 mm.

According to a thirteenth aspect of the present invention, in the image forming apparatus of the eleventh or twelfth aspect, the recovery member rotates in a counter direction with respect to a rotation direction of the image carrier or the intermediate transfer body. It is characterized by.

The invention according to claim 14 is the invention according to claims 1 to 1
3. The image forming apparatus according to item 3, wherein the recharging unit is capable of coming into contact with and separating from the image carrier or the intermediate transfer member.

According to a fifteenth aspect of the present invention, in the image forming apparatus of the fourteenth aspect, the recharging member and the recovery member can be individually brought into contact with and separated from the image carrier or the intermediate transfer member. It is characterized by the following.

The present invention according to claim 16 is based on claims 1 to 1.
In the image forming apparatus of the fifth aspect, the recharging member recharges the residual toner collected by the collection member.

According to a seventeenth aspect of the present invention, in the image forming apparatus of the sixteenth aspect, the recharging member comes into contact with or separates from the collection member.

[Operation] According to the above configuration, the residual toner on the intermediate transfer member is temporarily collected inside the recharging means for returning the residual toner on the image bearing member, and the residual toner collecting capability of the recharging means is obtained. Before the shortage occurs, the toner collected inside the recharging means is charged to a polarity opposite to that of the toner tribo charged in the developing section, and is electrostatically returned onto the intermediate transfer body. By transferring from the transfer body to the image carrier, it is possible to achieve the same effect as the above-mentioned obvi image while maintaining low cost and space saving.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in the figure is a laser beam printer using an intermediate transfer member, and the figure is a longitudinal sectional view showing a schematic configuration thereof.

The image forming apparatus shown in FIG. 1 uses a drum-type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image carrier, and a drum-type intermediate transfer member 2 having a two-layer structure. Uses an intermediate transfer drum.

The image forming apparatus shown in FIG. 1 will be described more specifically. The image forming apparatus has an intermediate transfer body 2 having a diameter of 18 mm.
This is a full-color electrophotographic image forming apparatus using a 6 mm intermediate transfer drum, a maximum paper passing size A3, a process speed of 117 mm / sec, image exposure, and reversal development. To form a full-color image, yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are sequentially formed on the photosensitive drum 1 that is driven to rotate in the direction of arrow R1. The toner images of the respective colors are sequentially transferred to the surface of the intermediate transfer member 2, and the toner images of four colors are superimposed on the surface of the intermediate transfer member 2. This transfer is carried out by the transfer between the photosensitive drum 1 and the intermediate transfer body 2.
This is performed via the next transfer nip N1. The transfer of the toner image from the photosensitive drum 1 to the intermediate transfer member 2 is referred to as primary transfer, and the toner image of four colors is superimposed on the surface of the intermediate transfer member 2 by rotating the intermediate transfer member 4 four times. Thus, the primary transfer is completed.

Next, the toner images of the four colors on the intermediate transfer body 2 are collectively transferred onto a transfer material P such as paper. This transfer is performed through a secondary transfer nip portion N2 formed between the intermediate transfer body 2 and the transfer unit 3, and is referred to as secondary transfer. The transfer unit 3 as a transfer unit is a unit in which a transfer belt 31 is stretched over two rollers 32 and 33, and the transfer belt 31 is intermediate-transferred by the transfer roller 32 on the upstream side in the transport direction of the transfer material P. The secondary transfer of the toner image is performed by bringing the transfer material P into contact with the body 2, and at the same time, the transfer material P is attracted to the transfer belt 31 to separate the toner image from the intermediate transfer body 2. The other roller is a drive roller 33, which drives the unit such that the peripheral speed of the intermediate transfer body 2 and the peripheral speed of the transfer belt 31 in the secondary transfer nip portion N2 are equal. The transfer unit 3 includes a driving roller 3
The transfer roller 32 is supported so as to be swingable around the third side, so that the transfer belt 31 can be moved toward and away from the intermediate transfer body 2.

The toner image secondary-transferred onto the transfer material P is
The transfer material P is fixed on the surface of the transfer material P by a heat fixing roller unit 11 as a fixing device disposed downstream of the secondary transfer nip portion N2 in the transport direction of the transfer material P. The transfer material P after the fixing of the toner image is discharged to the outside of the image forming apparatus main body.

Next, each member and each unit will be described in detail.

The photosensitive drum 1 is a negatively chargeable OPC (organic optical semiconductor) drum having a diameter of 62 mm, and its surface is first uniformly charged by a charging roller 7 as a primary charger. Here, the bias applied to the charging roller 7 is a bias in which a DC component and an AC component are superimposed.

Next, the surface of the photosensitive drum 1 is exposed by the laser exposure device 5. In this embodiment, image exposure is performed by combining an infrared laser diode having a wavelength of 760 nm and a polygon scanner, and using an exposure apparatus having a lens and a mirror.

Next, the electrostatic latent image formed by the laser exposure is developed with toner by a developing device. In the image forming apparatus of the present embodiment, four color toners of Y, M, C, and Bk are used. Specifically, a fixed black developing device 9 and a rotary color developing device as shown in FIG. The unit 10 is used.

The black developing device 9 employs a jumping developing method using a magnetic one-component toner. A conductive non-magnetic developing sleeve 91 having a diameter of 16 mm containing a fixed magnet roll is coated with a toner having a particle diameter of about 6 μm by an elastic blade 92, and is exposed by a DC component applied to the developing sleeve 91 and an AC component of a rectangular wave. Reversal development is performed by jumping with the drum 1.

The color developing unit 10 incorporates three yellow, magenta, and cyan developing units in a rotary rotary, and rotates the rotary developing unit in the direction of arrow R10 for the toner of the color used for development. By doing so, the photosensitive drum 1 is arranged at a developing position facing the photosensitive drum 1 to perform development.
The developing units for the respective colors perform development by a jumping development method using a non-magnetic one-component toner. The toner is a polymerized toner having a core / shell structure having a particle diameter of about 7 μm and containing wax therein. The toner is coated on the developing sleeve 101 by the application roller 103, the layer thickness is regulated by the elastic blade 102, and is sent to the developing position. , And is developed under the same bias conditions as in the case of the black developing device 9.

The primary transfer is performed by applying a voltage to the intermediate transfer body 2, and the primary transfer residual toner on the photosensitive drum 1 is removed by a cleaning blade 81 made of polyurethane elastomer.
Cleaning unit (cleaning device) 8 having
And is sent to a waste toner box via a waste toner transport roller 82 and a waste toner transport screw 83.

1 for single-color printing (single-color image formation)
After the next transfer, the toner image is transported as it is on the intermediate transfer body 2 to the secondary transfer nip portion N2, and undergoes the secondary transfer. In the case of four-color full-color printing (four-color full-color image formation), the intermediate transfer body 2 rotates four times to form Y, M, C,
After superimposing and primary transferring the respective toner images of Bk, 2
In the next transfer nip portion N2, secondary transfer is performed. In addition,
In the image forming apparatus of the present embodiment, by applying an appropriate voltage to the recharging means 4, the secondary transfer residual toner on the intermediate transfer body 2 is temporarily collected or recharged inside the recharging means 4. After the waste toner collected inside the means 4 is discharged onto the intermediate transfer body 2, the waste toner is transferred to the photosensitive drum 1. Further, the waste toner transferred to the photosensitive drum 1 is scraped off by the cleaning blade 81 and collected in the waste toner box.

The recharging means 4 used in the present embodiment includes a solid roller (recharging roller) 41 mainly made of acrylic rubber and having a diameter of 20 mm as a recharging member, and a 20 mm diameter collection made of rayon-based conductive yarn. It is composed of a brush roller (collection roller) 42 as a member, and is detachable from the intermediate transfer body 2.

The solid roller 41 has a three-layer structure of a low-resistance sponge layer made of an acrylic sponge, a resistance layer made of an acrylic urethane resin, and a surface release layer made of a fluororesin. The volume resistivity is the resistance layer ^{105 to 109}
Ω, and 10 ¹² to 10 ¹⁶ Ω for the surface release layer. Further, it can be detached from the intermediate transfer member 2 alone. The contact force is a total pressure of 100 to 300 g, rotates in the counter direction with respect to the rotation direction of the intermediate transfer member 2 (the direction of the arrow R2), and recharges the secondary transfer residual toner on the intermediate transfer member 2.

The fineness of the pile material of the brush roller 42 is 10
100-500 denier per 0 filament (preferably 300 denier), fiber density is 100-300 KF
/ Inch ² (preferably 200 KF / inch ² ). The amount of penetration into the intermediate transfer member 2 is 0.5 ± 0.3 mm, and the intermediate transfer member 2 rotates counterclockwise with respect to the rotation direction of the intermediate transfer member 2 to collect the secondary transfer residual toner on the intermediate transfer member 2 or Recharge.

In the case of monochromatic printing, the primary transfer bias is set to + 200V. In the case of performing four-color full-color printing, if the second transfer toner is further superimposed on the first transfer toner where the first transfer toner already exists on the intermediate transfer member 2, the transfer contrast is substantially reduced by the previous toner potential. Therefore, it is necessary to increase the transfer bias to compensate for the decrease. On the other hand, if the primary transfer bias is too high, discharge occurs between the photosensitive drum 1 and the intermediate transfer body 2,
Due to the deterioration of the image and the change of the toner tribo on the intermediate transfer body 2, a value that is too high cannot be taken. In view of these circumstances, the primary transfer bias during multicolor printing is 200 V, 300 for each rotation of Y, M, C, and Bk.
V, 300V, and 200V.

In this embodiment, in order to improve the secondary transfer efficiency, the toner of FIG.
Corona charging is performed by a pre-secondary-transfer corona charger 12 disposed to the right of the middle intermediate transfer body 2. The corona charger 12 in the figure is of a scorotron type, and supplies a DC current to the corona wire and superimposes an AC component to prevent the corona wire from being stained. The shield potential is grounded. Due to the corona charging, the tribo of the toner on the intermediate transfer body 2 is a black toner, and the negative charge of the toner increases from -10 μC / g to about −20 μC / g. During the secondary transfer, the transfer material P
Is supplied from a paper feeding unit (not shown), and the transfer belt 31 that can be separated and brought into contact with the intermediate transfer body 2. The secondary transfer bias performs constant current control, and the transfer material P
And the toner image on the intermediate transfer member 2 is secondarily transferred to the transfer material P.

The secondary transfer residual toner on the intermediate transfer member 2 is first charged positively by the solid roller 41, and then a negative bias is applied to the brush roller 42 on the downstream side so as to be charged in the recharging means 4 (mainly, (Attached to the brush of the brush roller 42). When the number of print counters reaches a predetermined number (100 in this embodiment), the solid roller 41 is separated from the intermediate transfer body 2 and the brush roller 42 is separated.
, And the toner (toner adhered to the brush roller 42) collected in the recharging means 4 is recharged to a positive value. Further, by making the bias (plus) of the brush roller 42 larger than the bias applied to the intermediate transfer member 2, the temporarily collected waste toner is discharged onto the intermediate transfer member, and the contact between the photosensitive drum 1 and the intermediate transfer member 2 is performed. The contact part 1
The toner is collected on the photosensitive drum 1 at the next transfer nip N1.

[0061] The solid roller 41
The mechanism for charging the remaining toner after transfer is based on discharge. In the discharge (small) gap between the solid roller 41 to which the voltage is applied and the intermediate transfer member 2, discharge is excited according to Paschen's law. Generally, the charging roller 7 of the photosensitive drum 1 is well known as a charging means based on such discharge.
All of the DC current supplied from the printer becomes the charging current of the photosensitive drum 1.

However, in the above-mentioned method, since both the intermediate transfer member 2 and the solid roller 41 are medium resistance members, not all the DC current supplied to the solid roller 42 contributes to charging, and most of the DC current is directly ohmic. The flowing injection current. Therefore, if the solid roller 41 is controlled at a constant current, when the resistance value of the member fluctuates due to environmental fluctuations or manufacturing variations, the ratio of the direct injection current to the current contributing to toner charging changes, and the solid roller 4
The toner tribo after one pass is not stable. Therefore, by adjusting the contact nip between the solid roller 41 and the intermediate transfer body 2 that directly contributes to the injection current, a discharge gap of 5 to 500 μm is maintained and the chargeability of the toner is secured.

The bias applied to the solid roller 41 is controlled by a constant current as a DC component (plus).
The component superimposes a 2 kHz, 3 kV _PP rectangular wave. AC
The reason why the bias is superimposed is that the discharge with only the DC bias occurs only in one direction and the charge amount is small, but when the AC is superimposed, the toner is discharged from both the intermediate transfer body 2 and the solid roller 41. This is because the chargeability is further improved by increasing the discharge gap.

As for the brush roller 42, when collecting the secondary transfer residual toner, the bias applied to the brush roller 42 is a DC component (minus) as in the case of the solid roller 41, and a constant current control is performed. 2kHz,
A rectangular wave of 3 kV _PP is superimposed. The reason for superimposing the AC bias is to make the tribo of the secondary transfer residual toner that cannot be completely collected by the brush roller 42 uniform and return it to the photosensitive drum 1 entirely. Also, when the waste toner temporarily collected by the recharging means 4 is discharged onto the intermediate transfer body 2, the bias applied to the brush roller 42 is a constant current as a DC component (plus) similarly to the solid roller 41. Control is performed, and the AC component superimposes a 2 kHz, 3 kV _PP rectangular wave. The reason why the AC bias is also superimposed is that the tribo of the toner discharged onto the intermediate transfer body 2 is
This is because all the components are returned to the photosensitive drum 1 by making the components uniform.

The operation sequence of the recharging means 4 described above will be described with reference to FIG.

Normally, the recharging means 4 (solid roller 4
1, the brush roller 42) is separated from the intermediate transfer body 2 (see FIG. 2A). After the primary transfer image is formed on the intermediate transfer member 2, the recharging means 4 (just before the primary transfer of the final color (Bk for four-color full-color printing or designated color for single-color printing)) is performed. Solid roller 41,
The brush roller 42) comes into contact with the intermediate transfer body 2 (see FIG. 2B). At the same time as the secondary transfer of the leading end of the toner image formed on the intermediate transfer body 2 is started, a predetermined bias is applied to the solid roller 41 and the brush roller 42, and the respective counter directions are applied to the intermediate transfer body 2 in the counter direction. (Direction of arrow R41, direction of arrow R42)
Next transfer residual toner is collected inside the recharging means 4. This secondary transfer residual toner collection sequence is repeated for each print.

Next, when the above-mentioned secondary transfer residual toner collecting mode is repeated 100 times (full color printing is counted once for one print, and single color printing is counted once for four prints), recharging is performed in the next print sequence. Means 4
The discharge mode of the waste toner collected in the above is executed. At this time, the state of the recharging means 4 is such that the unit of the recharging means 4 is in contact with the intermediate transfer member 2 as shown in FIG. As in the recovery mode, the intermediate transfer body 2 is in contact with the intermediate transfer body 2. On the other hand, the solid roller 41 is separated from the intermediate transfer body 2 and is in contact with the brush roller 42. The contact condition at this time is such that the tip of the brush of the brush roller 42 is 0.5 ± 0.3 with respect to the surface of the solid roller 41.
It is set to invade with mm. Then, after the waste toner discharge mode is performed once according to the bias condition set before, the secondary transfer residual toner collection mode is entered again, and the same operation is repeated thereafter.

However, when the image forming apparatus is abnormally stopped due to a density control sequence or a jam of the transfer material P, both the solid roller 41 and the brush roller 42 add the 2 kHz, 3 kV _PP rectangular wave AC component to the plus DC component. A superimposed bias is applied, and the toner on the intermediate transfer body 2 is returned to the photosensitive drum 1 directly without being collected inside the recharging means 4 (actually, the brush roller 42). to recover.

As described above, in the present embodiment, the configuration of the recharging means 4 includes a solid roller 41 for recharging waste toner and a brush roller 42 for collecting waste toner downstream of the solid roller 41. Not only eliminates the need to separately provide a cleaning unit for the intermediate transfer body 2, but also enables the waste toner to be reused for executing the black obi sequence for stabilizing the cleaning of the photosensitive drum 1 for a long period of time. This makes it possible to supply a stable image while maintaining space saving and low running cost.

In the first embodiment described above, the case where the recharging means 4 is applied to a four-color full-color image forming apparatus has been described as an example. However, the present invention is not limited to this. Can be applied. In this case, the recharging means 4 is arranged opposite to the surface of the photosensitive drum 1 between the transfer nip portion for transferring the toner image on the photosensitive drum 1 onto the transfer material P and the cleaning unit. The operation and effect in this case are the same as those in the first embodiment.

[0071]

As described above, according to the present invention,
A charging roller for recharging the residual toner on the intermediate transfer member,
A recharging unit having a charging brush for collecting the residual toner on the intermediate transfer body; temporarily collecting the residual toner on the intermediate transfer body into the inside of the recharging unit (charging brush); Before the residual toner collection capability of the brush is insufficient, the collected toner tribo is charged to a polarity opposite to that of the toner tribo charged in the developing unit, and is electrostatically returned to the intermediate transfer body. By transferring the collected toner from the transfer body to the image carrier and collectively collecting the toner by the image carrier cleaning device, while maintaining low cost and space saving,
Prevents problems such as scratches on the surface of the image carrier, fusing of toner on the surface of the image carrier, abnormal noise, abnormal vibration, and turning up of the blade, and enables the cleaning of the image carrier to be maintained in a stable state for a long time. became.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIGS. 2A, 2B, and 2C are schematic diagrams illustrating an operation state of a recharging unit in the image forming apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Intermediate transfer body (intermediate transfer drum) 3 Secondary transfer unit 4 Recharging means 8 Cleaning device (cleaning unit) 41 Recharging member (solid roller) 42 Collection member (brush roller) 81 Cleaning blade

Claims (17)

[Claims] 1. A toner image formed on a surface of an image carrier is transferred to a transfer material at a transfer nip portion, and residual toner not transferred to the transfer material and remaining on the surface of the image carrier is removed by a cleaning device. In the image forming apparatus, the image forming apparatus further includes a recharging unit disposed between the transfer nip portion and the cleaning device along a moving direction of the surface of the image carrier. A recharging member for recharging the residual toner remaining on the recharging member, and a collecting member disposed downstream of the recharging member and temporarily collecting the residual toner recharged by the recharging means. Characteristic image forming apparatus. 2. The method according to claim 1, wherein the toner images of different colors sequentially formed on the surface of the image bearing member are sequentially primary-transferred onto an intermediate transfer body at a primary transfer nip portion, and a plurality of color toner images are formed on the intermediate transfer body. After superimposing the images, the toner images of a plurality of colors on the intermediate transfer body are collectively and secondarily transferred onto a transfer material at a secondary transfer nip portion, and are not transferred to the intermediate transfer body during the primary transfer. A cleaning device removes residual toner remaining on the surface of the image carrier and residual toner remaining on the surface of the intermediate transfer member without being transferred to the transfer material at the time of secondary transfer and transferred to the image carrier. An image forming apparatus for removing, comprising: a recharging device disposed between the secondary transfer nip portion and the primary transfer nip portion along a moving direction of the surface of the intermediate transfer member; At the time of the secondary transfer A recharging member for recharging the residual toner remaining on the surface of the intermediate transfer member without being transferred to the transfer material; and temporarily disposing the residual toner disposed downstream of the recharging member and recharged by the recharging means. An image forming apparatus, comprising: a collecting member that collectively collects. 3. The image forming apparatus according to claim 1, wherein the residual toner temporarily collected by the collecting member is discharged from the circulating member to a collecting source at regular intervals. 4. The image forming apparatus according to claim 3, wherein the residual toner discharged from the collection member is removed by the cleaning device. 5. The image forming apparatus according to claim 1, wherein the collection member does not collect the residual toner during a density control sequence or an abnormal operation of the image forming apparatus. Image forming apparatus. 6. The rechargeable member has a volume resistance of 10 ⁵ to 10
The image forming apparatus according to claim 1, wherein the image forming apparatus is an elastic roller having a resistance of ¹³ Ω. 7. The image forming apparatus according to claim 6, wherein the recharging member is a multilayer elastic roller having at least a resistance layer and a surface release layer. 8. The image forming apparatus according to claim 6, wherein the recharging member contacts the image carrier or the intermediate transfer member at a total pressure of 100 to 300 g. . 9. The image according to claim 6, wherein the recharging member rotates in a counter direction with respect to a rotation direction of the image carrier or the intermediate transfer body. Forming equipment. 10. The collection member according to claim 1, wherein the collection member is a conductive brush.
10. The image forming apparatus according to 8 or 9. 11. The image forming apparatus according to claim 10, wherein the collection member has a roller shape. 12. The collection member, wherein the pile material has a fineness of 1
100 to 500 denier per 100 filaments, the fiber density is 100 to 300 KF / inch ² , and 0.5 ± 0.3 with respect to the image carrier or the intermediate transfer member.
The image forming apparatus according to claim 10, wherein the image forming apparatus has an intrusion amount of mm. 13. The image forming apparatus according to claim 11, wherein the collection member rotates in a counter direction with respect to a rotation direction of the image carrier or the intermediate transfer body. 14. The image forming apparatus according to claim 1, wherein the recharging unit is capable of coming into contact with and separating from the image carrier or the intermediate transfer body.
The image forming apparatus according to 8, 9, 10, 11, 12, or 13. 15. The image forming apparatus according to claim 14, wherein the recharging member and the collecting member can be individually brought into contact with and separated from the image carrier or the intermediate transfer member. apparatus. 16. The image forming apparatus according to claim 1, wherein the recharging member recharges the residual toner collected by the collecting member.
The image forming apparatus according to 8, 9, 10, 11, 12, 13, 14, or 15. 17. The image forming apparatus according to claim 16, wherein the recharging member contacts and separates from the collection member.