JPH0592604A - Image formation apparatus - Google Patents

Abstract

PURPOSE:To improve safety while reducing costs for providing insulation processings, driving IC's and others by a method wherein nonmagnetic toner is used instead of magnetic toner and the toner is carried by friction electrification. CONSTITUTION:After negatively electrifiable nonmagnetic toner of one component is stored in a container 16, developing biases Vi respectively in -400V and in 1500V are applied respectively to a developing roller 13 and a rear-side electrode plate and at the same time, cleaning bias in -200V is applied to a cleaning roller 14. With such conditions kept as they are, a toner pool is formed in a wedgeshaped space of a doctor blade 15 by rotating toner supply rollers 17 and 18 and after that, toner in the toner pool is electrified by friction between the doctor blade 15 and the developing roller and is also controlled in layer thickness. The toner layer controlled in thickness is then led, being carried by the developing roller 13, to a developing position facing a control grid 12. Thereby safety in operation can be improved while decreasing the cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a toner image can be directly adhered to a plain paper or other recording material without interposing a photosensitive drum or other latent image carrier, and particularly, to an electromagnetic type. Through the control grid in which the toner passage holes that can be opened and closed are arranged in a matrix, the toner carrier carrying the toner and the back electrode are arranged face-to-face, and the recording material is moved along the surface of the back electrode to display the image information. The present invention relates to an image forming apparatus configured to selectively open a toner passage hole while applying a corresponding control voltage to the control grid, and transfer the toner carried on the toner carrier to the recording material side through the passage hole. ..

[0002]

2. Description of the Related Art Image formation in which toner carried on a developing roller is directly transferred to a recording material in a dot pattern corresponding to image information without using a photosensitive drum functioning as a latent image carrier has hitherto been performed. The apparatus is well known (Sweden Patent Application No. 8704883, etc.). A brief description of such an apparatus configuration will be given based on the schematic diagram shown in FIG. 5 previously filed by the present applicant. The developing roller 50 is rotatably rotatably supported, and a toner container having a strip-shaped opening 51a formed on the lower surface side, 53 is a matrix-shaped control grid stretched over the strip-shaped opening 51a, and 52 is a predetermined gap with the control grid 53. Back electrodes, which are arranged face-to-face with each other,
4 is a power supply circuit for applying a developing voltage to the back electrode 52, 5
Reference numeral 5 denotes a control circuit for generating a signal corresponding to image information, 56
Is a drive circuit for switching the control grid 53 based on the signal, and 57 is a spring 57a biased from the bottom surface.
It is a support plate that positions and fixes the back electrode 52 at a predetermined position via the. To briefly explain the operation of such an apparatus, the magnetic toner contained in the toner container 51 is guided to the developing position facing the control grid 53 after the layer thickness is regulated by the doctor blade 51b, while at the developing position. A developing electric field is applied between the developing roller 50 and the back electrode 52 by a power supply circuit 54 provided on the back electrode 52 side.

In this state, the control grid 53 is moved to the X position based on the signals from the control circuit 55 and the drive circuit 56.
By controlling the energization in the Y-axis direction, the developing electric field acting on the matrix-shaped toner passage holes 53a is selectively cut off or made conductive in correspondence with the image information to synchronize with the image information on the surface of the back electrode 52. Let recording material 5
By inserting 8 through the toner passage hole 53a, the toner corresponding to the image information is transferred from the developing roller 50 to the recording material 58 side, and a predetermined image can be formed.

According to this technique, the toner carried on the toner carrier is selectively transferred onto the recording paper through the toner passage holes while moving the recording paper along the flat back electrode surface as described above. In other words, since the toner carrier is arranged above the back electrode (upstream in the direction of gravity), the toner on the carrier is prevented from falling due to gravity. Therefore, in the conventional apparatus, the toner is formed of a magnetic toner, and a magnetic assembly is included in the toner carrier to prevent the magnetic force of the assembly. It is used to carry toner.

[0005]

However, when the toner is carried by using the magnetic force as described above, the developing electric field applied to the developing position must be strong enough to overcome the magnetic field, that is, The developing bias voltage applied to the back electrode becomes large, and the control voltage of the control grid must be set correspondingly. Therefore, as a result, the insulating film treatment of the control grid, the driving IC, and the power supply circuit. Not only did it lead to higher costs, but there was also a safety issue.

Further, it is difficult for the magnet assembly to set the magnetic force distribution uniformly in the developing width direction. Therefore, in the case of an apparatus capable of directly rubbing the surface of the photosensitive drum like the magnetic brush development of the Carlson method. The uneven magnetic force distribution is not affected by the image density, but in the apparatus having the structure of flying the toner and transferring it to the recording material side as in the present invention, the uneven magnetic force distribution greatly affects the image density. It will affect.

Further, according to the above technique, in order to obtain an appropriate image density, it is necessary to maintain the developing gap between the toner carrier and the back electrode with high accuracy. However, as described above, the back electrode and the control grid are flat. Despite the shape, the developing roller forming the toner carrying member has a cylindrical shape. Therefore, if the accuracy of the gap is increased, the developing width must be narrowed as a result. This causes a decrease in development speed. In order to eliminate such a drawback, the toner carrying surface may be flattened by using a developing belt for the toner carrying body, but it is difficult to flatten the included magnet assembly without causing non-uniformity of the magnetic field. Is.

In view of the above-mentioned drawbacks of the prior art, the present invention makes it possible to set the control voltage applied to the control grid together with the developing bias to a low level, thereby reducing the cost of the insulating film processing, the driving IC and the like, and at the same time, ensuring safety An object of the present invention is to provide an image forming apparatus having improved property. Another object of the present invention is to provide an image forming apparatus in which unevenness in image density does not occur, application to colorization is easy, and a developing width can be easily expanded.

[0009]

The first aspect of the present invention is to use a non-magnetic toner without using a magnetic toner and to carry the toner by frictional charging. Therefore, the present invention is required to have a toner carrier having a conductor surface coated with an insulating layer, a non-magnetic toner, and a frictional charging means. That is, if the surface is not covered with an insulating layer, the charge will escape,
It becomes impossible to carry the toner, and unless a conductor is provided inside, it is difficult to form a developing electric field with the back electrode. Further, the toner carrier may be formed of a roller member, or may be formed of a belt member having a conductive layer surface coated with an insulating layer.

The non-magnetic toner may be either a one-component developer or a two-component developer. As the frictional charging means, an independent frictional charging means using a doctor blade may be used, or frictional charging may be performed by rubbing against a carrier like a two-component developer.

However, it is quite difficult to support the toner against gravity by only the triboelectric charging of the toner.
Therefore, in the present invention, the toner carrier is arranged downstream of the back electrode in the direction of gravity, and toner is carried by both the force of gravity and the frictional power.

Now, as described above, in the structure in which toner is carried mainly by utilizing triboelectric charging without using the magnet assembly,
When toner triboelectric charging is repeatedly performed with the residual toner after development attached, a difference in frictional electrification power is generated between the charged residual toner and the new toner in the non-charged state.
It becomes difficult to perform uniform charging.

Therefore, in the second aspect of the present invention, a cleaning means is disposed in contact with the toner carrier formed of an endless body on the downstream side of the position facing the back electrode in the rotational direction, and the recording means is utilized. The residual toner after flying to the material side is removed, and new non-magnetic toner can be always attached to the toner carrier side by the triboelectric charging.

When the toner layer is formed by frictional charging as described above, the distance between the back electrode and the back electrode can be narrowed by that amount because the toner layer carried by the toner carrier is extremely thin. As a development electric field can be set small,
On the contrary, since the control grid is also arranged in the developing interval, it becomes difficult to maintain the interval setting of these members with high accuracy.

The apparatus can be applied to either a one-component developer or a two-component developer. In the case of a two-component developer, for example, when a conductive carrier is used, it is carried on a toner carrier. This is impossible, and it is possible to carry the carrier by using an insulating carrier. However, since the carrier is considerably larger than the toner particle size, the distance between the toner carrier and the back electrode must be wide. Of course, the developing bias must be set to a large extent correspondingly, and if an insulating carrier exists between the toner carrier and the back electrode, the carrier acts in the direction of disturbing the developing electric field, which is not practical.

The invention according to claim 3 solves the above-mentioned drawbacks, and particularly satisfies the conflicting requirements that the developing electric field can be set small while widening the distance between the toner carrier and the back electrode. The feature is that, as shown in FIG. 4, the carrier 30 in which the surface of the conductive particles 31 is coated with the insulating layer 32 is used, and as shown in FIG. In the supported state, the developing bias is applied from the back electrode 11 side.

According to the invention, since the carrier 30 is covered with the insulating layer 32 around the conductive particles 31, the toner 35 and the carrier 30 are triboelectrically charged and the toner 35 adheres to the periphery of the carrier 30. .. Then, in this state, the carrier 30 functions as a floating electrode, and a developing electric field is formed between the carrier 30 and the back electrode, not with the toner carrier. Therefore, even if the distance between the toner carrier 40 and the back electrode 11 is wide, the actual developing electric field distance is the distance L between the carrier 30 and the back electrode 11 accumulated on the carrier, It is possible to narrow the amount, and as a result, the developing electric field strength can be reduced accordingly.

The so-called carrier 3 is obtained by incorporating magnetic powder into the carrier 30 to form the magnetic carrier 30 and enclosing the magnet assembly 41 in the toner carrier 40.
It is possible to raise the height of 0, and it is possible to further reduce the distance between the carrier 30 and the back electrode 11. The toner 35 used in the present invention is not limited to non-magnetic toner, but
The effect of the first invention can be obtained by using a non-magnetic toner.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail below as an example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Not too much.

FIG. 1 shows a schematic structure of an image forming apparatus according to an embodiment of the present invention. To briefly explain the structure along the flow direction of recording paper, 1 is a paper feed cassette and 2 is the paper feed. A paper feed roller for feeding the recording paper from the cassette 1 to the conveyance path side,
3 is a registration roller, 4 is an image forming unit including a back electrode plate 11, a control grid 12, and a developing roller 13, 6 is a fixing roller pair, 7 is a separating claw, 8 is a reversing guide, 9 is a paper discharge roller, and 10 is a paper discharge roller. It is a paper tray.

The image forming unit 4 includes a rear electrode plate 11 and a control grid 12 from above from above with the recording paper conveying path interposed therebetween.
Further, the developing roller 13 is disposed below the control grid 12, and the periphery of the developing roller 13 except the upper surface side is surrounded by the toner container 16 and the container 16 is provided.
The control grid 12 is fixed to the frame body at the upper end of the. Further, guide members 111 that can be accurately inserted into the lower surface of the rear electrode plate 11 are provided at both end sides of the recording paper on the lower surface of the rear electrode plate 11 which are orthogonal to the insertion direction of the recording paper while controlling the position of the recording paper.

The developing roller 13 is a metal shaft 131.
A conductive rubber 133 containing carbon is surrounded around the core 132 penetrating the core, and the surface thereof is covered with an insulating layer 134 having abrasion resistance.

On the other hand, the cleaning roller 14 is in contact with the developing roller 13 on the downstream side in the rotational direction from the developing position, and the doctor blade 15 is in contact with the upstream side of the developing position.
In the wedge-shaped space formed between the doctor blade 15 and the developing roller 13, toner supply rollers 17 and 18 which rotate in the direction of the arrow so that a toner pool can be accumulated are disposed. The cleaning roller 14 may be formed of a conductive roller that peels off the residual toner in an electric field as shown in this embodiment, but it may be formed of a fur brush brush roller.

Next, the operation of the present embodiment will be described in detail. First, the negatively charged one-component non-magnetic toner is stored in the container 16, and then the developing roller 13 is
A developing bias Vi of 1500V is applied to the rear electrode plate 11 of 400V, and a cleaning bias Vc of -200V is applied to the cleaning roller 14 while being applied.

In this state, first, the toner supply rollers 17 and 1
8 is rotated in the direction of the arrow to form a toner pool in the wedge-shaped space of the doctor blade 15, and then the developing roller 13 is rotated to frictionally charge the toner located in the toner pool with the doctor blade 15. While the layer thickness is regulated, the toner layer whose layer thickness is regulated is carried to the developing position facing the control grid 12 while being carried by the developing roller 13. At the developing position, the back electrode plate 11
A developing electric field having a polarity opposite to the charging potential of the toner is formed between the developing roller 13 and the developing roller 13, and the control grid 12 is energized and controlled in the XY axis directions based on the control pulse signal P, so that the matrix toner The developing electric field acting on the passage hole 12a can be selectively cut off or made conductive in correspondence with image information, whereby the recording paper inserted on the surface of the back electrode 11 via the resist roller 3 is resistant to gravity. Then, the toner flying from the developing roller 13 adheres to the recording paper side, and a predetermined image can be formed.

After the development is completed, the toner remaining on the developing roller 13 is removed by using the cleaning bias applied to the cleaning roller 14, and the above operation is repeated.

In the present invention, it is also possible to use a developing belt as shown in FIG. 2 without using the developing roller as described above. The structure of the image forming unit 4 ′ will be described focusing on the differences from the above-mentioned embodiment. The image forming unit 4 ′ has a rear electrode plate 11 and a control grid 12 arranged from above with the recording paper conveyance path interposed therebetween. Similar to the technique, a developing belt 23 stretched by a pair of rollers 24 and 25 is arranged below the control grid 12 in parallel in a substantially horizontal direction, and a belt except for the upper surface side of the developing belt 23. 23
The circumference is surrounded by the toner container 26.

The developing belt 23 is stretched by a tension roller 21 urged by a spring 27 on the downstream side in the belt circulation direction and a circulation roller 22 on the upstream side, and the control grid is provided via the belt 23. A conductive developing electrode plate 28 is disposed on the back side of the belt 23 facing the belt 12, and a voltage of −400 V is applied to the developing belt 23 via the electrode plate 28.

On the other hand, the tension roller 24 is provided with a fur brush-like cleaning roller 14 sandwiching the belt 23. In such an embodiment, the development belt 2 together with the control grid 12 and the back electrode plate 11 are
Since the flat portion 3 is formed in parallel and in a flat shape, the developing width can be set to be equal to that of the flat portion of the belt 23, whereby the image sharpness can be improved and the recording speed can be increased. ..

FIG. 3 shows a main structure of an image forming apparatus used for a two-component developer. The difference from the above embodiment will be mainly described. The developing roller 40 is a hollow non-magnetic sleeve having an insulating coating on its surface. And a fixed magnet assembly 41 in the sleeve 40.
To include. Since the developing roller 40 merely holds the carrier 30 magnetically, it is -4 as in the above embodiment.
No voltage of 00V is applied and there is no need for grounding. As the cleaning roller 44, a fur brush-like cleaning brush roller is used to peel off the carrier 30 magnetically carried together with the non-magnetic toner 35, and a peeling voltage is not applied, especially unlike the above embodiment.
Further, the doctor blade 45 is separated from the developing roller 40 at a minute interval without coming into contact with the developing roller 40. In this embodiment, a developer composed of magnetic carrier 30 and non-magnetic toner 35 is used.

FIG. 4 is a schematic diagram showing the carrier 30 used in this embodiment, in which the toner 3 is formed on the surface of carrier mother particles 31 in which magnetic powder 33 is uniformly dispersed in a binder resin.
5 is coated with an insulating coating layer 32 having a polarity opposite to that of 5, which is easy to be positively charged and has high wear resistance. The particle size of the carrier 30 is preferably 50 to 100 μm, which is about 3 to 10 times larger than the toner particle size.

Next, the operation of the present embodiment will be described in detail. First, the one-component non-magnetic toner 35 that is negatively charged is first stored in the container, and then the back electrode plate 11 is set to 1
After applying a developing bias of 000 V, the toner supply rollers 17 and 18 are rotated in the direction of the arrow to accumulate the toner 35 together with the carrier 30 in the wedge-shaped space of the doctor blade 16, and the developing roller is rotated. The carrier 30 and the toner 35 are rubbed against each other within a minute gap between the doctor blade 25 and frictionally charged, and the toner 35 is adsorbed around the carrier 30, and the layer thickness is regulated. Is a fixed magnet assembly 4
It is guided to the developing position facing the control grid 12 while being carried by the developing roller by utilizing the magnetic force of 1.

At the developing position, the magnetic force of the magnet assembly 41 causes the carrier 30 to quasi-peak while being brought close to the control grid 12 side. Back electrode plate 1
A developing electric field is formed between the two, and the control grid 12 is energized and controlled in the X-Y axis directions based on the control pulse signal, so that the matrix-shaped toner passage holes 12a are formed.
It is possible to selectively block or conduct the developing electric field that acts on the recording paper in correspondence with the image information, thereby developing the recording paper inserted on the surface of the back electrode 11 via the resist roller 3 against gravity. The toner 35 flying from the roller 40 can be attached to the recording paper side.

After the development is completed, the carrier 30 held on the developing roller 13 is wiped off to the toner container 46 side by the rubbing of the cleaning brush roller 44.
The above operation is repeated thereafter.

[0035]

As described above, according to the first aspect of the present invention, since the non-magnetic toner is used without using the magnetic toner, and the toner is carried by frictional charging, the control for applying to the control grid together with the developing bias is performed. It is possible to set the voltage low, which allows insulation film processing and drive I
C and other costs can be reduced, and safety can be improved. Further, since the present invention forms an image by frictional charging without using a magnet assembly, uneven image density does not occur. Further, since non-magnetic toner is used instead of magnetic toner, it is possible to arrange a plurality of the image forming units along the conveyance direction of the recording paper to correspond to colorization, which is easy to apply to colorization. is there. Further, not only the developing roller but also the developing belt can be used, so that the developing width can be easily expanded. The second invention according to claim 3 uses a conductive carrier coated with an insulating layer,
The developing electric field can be set small while widening the space between the toner carrier and the back electrode, and as a result, the developing electric field strength can be reduced accordingly, leading to safety and cost reduction. And so on.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus using a one-component developer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of an image forming apparatus according to another embodiment of the present invention using a one-component developer.

FIG. 3 is an overall configuration diagram of an image forming apparatus using a two-component developer according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a carrier used in the device of FIG.

FIG. 5 is an overall configuration diagram of an image forming apparatus according to a conventional technique.

[Explanation of symbols]

 13, 23, 41 Toner carrier 12 Control grid 11 Back electrode 15 Friction charging means 30 Carrier

Claims (4)

[Claims] 1. A toner carrier and a back electrode, on the surface of which a recording material is movable, are arranged facing each other through a control grid in which a group of electromagnetically openable and closable toner passage holes are arranged in a substantially matrix. In the image forming apparatus, the toner carrier whose surface is covered with an insulating layer is arranged downstream of the back electrode in the direction of gravity, and after the non-magnetic toner is carried on the toner carrier by frictional charging, With the developing electric field applied between the toner carrier and the back electrode, the non-magnetic toner can fly against the gravity on the recording material moving along the back electrode surface through the control grid. Image forming apparatus characterized by 2. A cleaning means is disposed in contact with the toner carrier formed of the endless body on the downstream side of the position facing the back electrode in the rotational direction, and after the cleaning means is used to fly to the recording material side. Image forming apparatus in which the residual toner of the above is removed, and new non-magnetic toner can be always adhered to the toner carrier side by the triboelectric charging. 3. A toner carrier and a back electrode, on the surface of which a recording material can move, are arranged facing each other via a control grid in which a group of electromagnetically openable and closable toner passage holes are arranged in a substantially matrix. In the image forming apparatus, a two-component developer including a carrier in which conductive particles are coated with an insulating layer is used, and the carrier is carried on the toner carrier together with the toner, and a developing bias is applied from the back electrode side. Image forming apparatus characterized by being configured as possible 4. An image forming apparatus according to claim 3, wherein the toner is a non-magnetic toner and the carrier is a magnetic carrier.