JP2002148911A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of image unevenness due to the fluctuation of a gap between a writing electrode and an image carrier fluctuated by end leakage toner. SOLUTION: The image forming device which transfers a toner image developed by an image carrier 2 or the toner image of the above toner image transferred temporarily by an intermediate transfer member 5 is transferred on a recording medium transported by a recording medium transport means is provided with a write means 3 which has a plurality of writing electrodes 3b contacted with or disposed closely to the image carrier 2 along the axial direction of the image carrier 2 and forms an electrostatic latent image on the image carrier 2, and a cleaning means which contacts with the recording medium transport means to remove residual toner or a cleaning means 11 which contacts with the intermediate transfer member to remove residual toner. The uneven adhesion of toner to the contact parts of the write means 3 and the image carrier 2 is prevented by making at least the width of the image carrier 2 larger than the width of the write means 3 and making the contact width of the cleaning means 11 larger than the width of the image carrier 2.

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 for directly transferring a toner image developed on an image carrier to a recording medium conveyed by a recording medium conveying means, or a method for transferring the toner image to an intermediate transfer member. The present invention relates to an image forming apparatus for transferring and secondarily transferring a toner image of the intermediate transfer member to a recording medium.

[0002]

2. Description of the Related Art A multi-needle electrode type image forming apparatus for forming an electrostatic latent image on an image carrier using a large number of needle electrodes is known. In this multi-needle electrode type image forming apparatus, a needle electrode and an image carrier are arranged in a non-contact manner with a small gap, and an electrostatic latent image is formed on the image carrier by discharge from the needle electrode. A needle electrode having a sharp tip is desirable as the discharge portion because the discharge start voltage is low and the image resolution is improved.

However, since the gaps are arranged in a non-contact manner with a small gap, it is difficult to keep the gap constant. Variations in the discharge start voltage due to gap variations directly result in variations in the potential of the electrostatic latent image. It leads to serious image defects such as discontinuity of image, blur, and dust. Therefore,
In order to stably maintain the gap constant, the needle electrode needs to have high precision and high rigidity, and a holding member for positioning and holding the needle electrode also needs to have high precision and high rigidity.

Further, unless the needle electrode is accurately positioned on the generatrix of the image carrier also in the circumferential direction of the image carrier, the gap changes and uniform charging cannot be performed. In addition, spacers and the like are added to manage the gap in order to reliably change the gap due to the rotational fluctuation of the image carrier.However, in high-speed printing where the image carrier rotates at high speed, the gap can be kept constant by vibration or the like. However, as a result, the printing speed was kept low.

In order to solve these problems, Japanese Patent Publication No. Sho 63
JP-45104A proposes that a needle electrode is brought into contact with an image bearing member coated with inorganic glass, and further, lubricating oil is applied to the image bearing member to prevent wear damage of the needle electrode to the image bearing member. It is carried out.

However, Japanese Patent Publication No. 45104/1988 has a problem that the needle electrode is worn and the firing voltage fluctuates, and the size of the electrostatic latent image and the charging potential fluctuate. are doing. Further, since the configuration in which oil is applied to the image carrier is an essential requirement for reducing wear, the toner image cannot be directly developed, and the image carrier can be used only as an intermediate image carrier. .

As described above, the multi-needle electrode system has a problem that the image quality is deteriorated because the potential of the electrostatic latent image easily varies and the resolution of the electrostatic latent image also changes with time. A high-precision holding member and a positioning member for positioning and a gap with the carrier are required, which causes a problem that the device becomes complicated and large. In addition, since the contact pressure is high due to the needle electrode, there is a problem that the electrode and the image carrier are damaged in a short time, it is difficult to speed up printing, and the device is enlarged as it is used as an intermediate image carrier. There is a problem that.

In order to solve this problem, the present applicant has
There has been proposed an image forming apparatus in which a base material of a writing device is brought into elastic contact with an image carrier and an electrostatic latent image is formed on the image carrier by a writing electrode provided on the base material. According to this image forming apparatus,
When forming an electrostatic latent image on the image carrier by sending a write signal to the electrode portion, stabilize the contact between the substrate and the image carrier,
Uniform writing becomes possible, and a good image without image unevenness or streaks can be obtained.

[0009]

However, even in the above-mentioned image forming apparatus, since the base material of the writing device is brought into elastic contact with the image carrier, even if the toner remaining after transfer is removed by the cleaning means, the end portion thereof is not removed. Due to the toner leakage, there is a problem that the toner leaking from the end adheres to the contact portion between the writing electrode and the image carrier via the lower surface of the base of the writing device. Then, the gap between the electrode and the image carrier fluctuates due to the toner attached to the contact portion between the writing electrode and the image carrier, resulting in a problem that image unevenness appears.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is intended to prevent the gap between a writing electrode and an image carrier from fluctuating due to toner leaking from an end portion, thereby causing image unevenness. It is to prevent it.

[0011] For this purpose, the present invention provides an image forming apparatus in which a toner image developed on an image carrier is primarily transferred to an intermediate transfer member and the toner image of the intermediate transfer member is transferred to a recording medium. Writing means for forming an electrostatic latent image on the image carrier having a plurality of write electrodes arranged in contact with or close to the image carrier along the axial direction; A cleaning unit for removing toner, wherein the width of the image carrier is at least larger than the width of the writing unit, and the contact width of the cleaning unit with the intermediate transfer member is larger than the width of the image carrier. It is characterized by having done.

Also, in an image forming apparatus for transferring a toner image developed on an image carrier to a recording medium conveyed by a recording medium conveying means, the toner image is brought into contact with or near the image carrier along the axial direction of the image carrier. A writing unit having a plurality of writing electrodes disposed thereon and forming an electrostatic latent image on the image carrier; and a cleaning unit abutting on the recording medium transporting unit and removing residual toner, wherein at least the The width of the image carrier is larger than the width of the writing unit, and the contact width of the cleaning unit with the recording medium conveying unit is larger than the width of the image carrier.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view showing an embodiment of the image forming apparatus according to the present invention. Carrier, 3 is a writing device, 3a is a substrate,
3b is a writing electrode, 3c is a driver, 3d is a conductive pattern, 4 is a developing device, 5 is an intermediate transfer belt, 6 is a transfer roller, 7 and 11 are cleaning blades, 12 and 13 are belt support rollers, and L2 is an image carrier. L3 indicates the writing device width, and L11 indicates the cleaning blade width.

The image forming apparatus according to the present invention prevents the toner T leaking from the edge of the cleaning blade 11 on the image carrier 2 shown in FIG. 1 from adhering to the edge of the image carrier 2.
Further, the writing width of the writing device 3 in contact with the image carrier 2 is set so that even if the toner T leaking from the end portion adheres to the end of the image carrier 2, the toner does not go around the lower surface of the writing device 3. The width L2 of the image carrier is made larger than the width L3 of the mounting device, and the width L2 of the cleaning blade 11, which is the contact width of the cleaning blade 11 with the intermediate transfer belt 5, is further increased.
1 is to be increased. By setting the relationship between the widths to L3 <L2 <L11, the toner T leaking from the end of the cleaning blade 11 that contacts the intermediate transfer belt 5 and removes the residual toner adheres to the image carrier 2. As a result, the end leakage toner T does not come around the lower surface of the base material of the writing device 3, and the end leakage toner T contacts the contact portion between the writing electrode 3 and the image carrier 2. No longer adheres.

Further, each component of the image forming apparatus according to the present invention will be described in detail. 1 and 2, an image forming apparatus 1 according to the present invention includes an image carrier 2 on which an electrostatic latent image is formed, and an electrostatic latent image formed on the image carrier 2 by contacting the image carrier 2. Writing device 3 for writing, developing device 4 for developing the electrostatic latent image on image carrier 2 with toner, and intermediate transfer for primary transfer of the toner image on image carrier 2 developed by developing device 4 A belt 5 and a transfer roller 6; and a cleaning blade 7 for removing toner remaining on the image carrier 2 after the transfer.
And a cleaning blade 11 for removing toner remaining on the intermediate transfer belt 5 after the transfer, and belt support rollers 12 and 13 for supporting the intermediate transfer belt 5. The writing device 3 has one end supported by a fixed portion in a cantilever manner, and the other end in contact with the image carrier 2.

As shown in FIG. 2B, the writing device 3
PC (Flexible Print Circuit) or PET (Polyet
hylen Terephtalate) A flexible base material 3a having a high insulating property such as a film and relatively soft and elastic, and a base material 3a
And a writing electrode 3b that is lightly pressed onto the image carrier 2 with a weak elastic restoring force due to the bending of the base material 3a and is arranged in contact with or in proximity to the image carrier 2. A driver 3c and a conductive pattern 3d are formed on the substrate 3a, and are connected to the write electrode 3b. Note that the writing electrode 3
The pressing force b is preferably 300 mm in width and 10 N or less in pressing force, that is, 0.33 N / mm or less in linear pressure, from the viewpoint of stabilizing contact and stabilizing charge injection or discharge (void). It is desirable to reduce the linear pressure as much as possible while maintaining a state in which is stable.

As described above, in the writing device 3 having the plurality of writing electrodes 3b which are in contact with or close to the image carrier 2 along the axial direction of the image carrier 2, the image carrier 2 and the intermediate transfer belt When the toner slightly leaking from the end of the cleaning blade 11 remaining on the cleaning device 5 unevenly adheres to the contact portion between the writing device 3 and the image carrier 2, the contact pressure between the writing device 3 and the image carrier 2 fluctuates. Or contamination of the write electrode 3b, thereby inhibiting the formation of a latent image and causing image unevenness.

Therefore, the image forming apparatus according to the present invention eliminates this obstruction factor by removing the image carrier width L of the image carrier 2.
2 is a writing device width L3 at which the writing device 3 contacts the image carrier 2.
The cleaning blade width L11 at which the cleaning blade 11 contacts the intermediate transfer belt 5 is made larger than the image carrier width L2. As a result, it is possible to first prevent the toner leaking from the end of the cleaning blade 11 from adhering to the image carrier 2. Therefore, since the end leakage toner does not adhere to the image carrier 2, the end leakage toner of the cleaning blade 11 wraps around the image carrier 2 to the contact portion between the writing device 3 and the image carrier 2 and adheres. Can be prevented, and the above-described obstructive factors of latent image formation are eliminated.

Next, the image carrier width L is calculated from the writing device width L3.
2. The effectiveness of making the cleaning blade width L11 larger than the image carrier width L2 will be described. FIG. 3 is a view showing an example of the case where the toner leaking from the end adheres to the writing device 3 via the intermediate transfer belt 5 and the image carrier 2 and accumulates, and FIG. 4 illustrates the generation of the toner leaking from the end seal. FIG.

The writing device 3 has a writing auxiliary electrode for adjusting the image position with respect to the maximum image width.
In order to ensure that b contacts the image carrier 2 stably, the base material 3a has a margin L outside the end electrode 3b as shown in FIG. If the margin L is not ensured, the contact pressure of the electrode near the end electrode 3b with the image carrier 2 becomes smaller than that of the writing electrode at the center, and uniform writing cannot be performed. On the other hand, at the contact interface between the cleaning blade 11 and the end seal 11a, the toner cannot be completely cleaned as shown in FIG.
Stick on top.

In general, in relation to the writing device 3, the cleaning blade 11 only needs to have a dimension equal to or larger than the maximum sheet width, but the outside of the cleaning blade 11 is a toner area where cleaning is left unfinished (edge leakage). . Therefore, the cleaning blade 11 is wider than the width L3 of the writing device 3.
If the width L11 of the cleaning blade contacting the intermediate transfer belt 5 is small, the residual toner remaining after cleaning adheres little by little to the end of the writing means 3 as shown in FIG. The contact becomes unstable with time, and the gap between the electrode and the image carrier 2 fluctuates, which results in image unevenness.

Accordingly, in the present invention, as shown in FIG. 1, the width L2 of the image carrier is made larger than the width L3 of the writing device, and the width L2 of the cleaning blade is made larger than the width L2 of the image carrier.
11 is increased. As a result, the toner leaking from the edge of the cleaning blade 11 does not adhere to the image carrier 2. Therefore, the toner leaking from the edge of the cleaning blade 11 wraps around the edge of the writing device 3 via the image carrier 2. , It is possible to prevent factors that hinder the formation of a latent image, and it is possible to form an image stably over time.

Further, detailed embodiments of the image forming apparatus to which the present invention is applied will be described in detail. 5 and 6 are diagrams for explaining the principle of writing an electrostatic latent image by charging the writing electrode 3b of the writing device 3, and FIG. 5A shows the writing electrode 3b and the image carrier. 5 (B) is an electrical equivalent circuit diagram of the contact portion, and FIGS. 5 (C) through 5 (C).
FIG. 6F is a diagram showing the relationship between each parameter and the surface potential of the image carrier 2. FIG. 6A is a diagram illustrating charging of the image carrier by charge injection, and FIG. 6B is an image carrier by discharge. FIG. 6C is a diagram for explaining Paschen's law.

The image carrier 2 is made of a conductive material such as aluminum, and has a grounded base 2c as shown in FIG. 5A and an insulating property formed on the outer periphery of the base 2c. And a charging layer 2d. This charged layer 2d
On the other hand, the writing electrode 3b is supported by the base material 3a made of FPC or the like of the writing device 3, and is in contact with the predetermined light pressing force directly or via the base material 3a as described above, The body 2 is moving (rotating) at a predetermined speed v. A predetermined high voltage V ₀ or a predetermined low voltage V ₀ is applied to the write electrode 3b.
₁ is selectively switched and applied via the base material 3a.

That is, an electrical equivalent circuit shown in FIG. 5B is formed on the contact surface (nip portion) between the writing electrode 3b and the image carrier 2. In FIG. 5B, R
Indicates the resistance of the writing electrode 3b, and C indicates the capacitance of the image carrier 2. Resistance R of the writing electrode 3b is the A side - is adapted to be selectively switched for connection to a predetermined voltage V ₀ or the ground voltage V ₁ of the B-side ().

In the equivalent circuit, the write electrode 3b is connected to the A side, and the resistance R of the write electrode 3b and the resistance of the image carrier 2 when a predetermined voltage V ₀ (−) is applied to the write electrode 3b. relationship between the surface potential is 5 predetermined voltage V ₀ becomes the surface potential of the image carrier 2 in the region resistance R of the writing electrode 3b is small as shown by the solid line is a constant (C), the writing electrodes 3b If the resistance R is larger than a predetermined value, the absolute value of the surface potential of the image carrier 2 decreases. On the other hand, when the write electrode 3b is connected to the B side and the write electrode 3b is grounded, the relationship between the resistance R of the write electrode 3b and the surface potential of the image carrier 2 is shown in FIG.
Approximately ground voltages V ₁ becomes the surface potential of the resistor R is small in a region of the image carrier 2 the writing electrode 3b as indicated by the dotted line is constant, the resistance R of the writing electrode 3b is a larger area than a predetermined value Then, the absolute value of the surface potential of the image carrier 2 increases.

[0027] In the region which is a predetermined voltage V ₀ or constant at the ground voltage V ₁ of the resistor R is small surface potential of the image carrier 2 is constant writing electrode 3b, the image as shown in FIG. 6 (A) Between the writing electrode 3b in contact with the carrier 2 and the charged layer 2d of the image carrier 2, charge injection of (-) charge is performed directly from the lower voltage to the higher voltage, and the image carrier 2 is charged. Is charged. Further, the resistance R of the writing electrode 3b is large,
In the region where the surface potential starts to change, the charging of the image carrier 2 due to charge injection gradually decreases, and the resistance R of the writing electrode 3b increases, as shown in FIG. Discharge starts to occur between the image carrier 3a and the image carrier 2.

The discharge between the substrate 3a and the substrate 2c of the image carrier 2 occurs when the voltage between the substrate 3a and the image carrier 2 becomes higher than the discharge starting voltage. Lumber 3
a and the gap between the image carrier 2 and the discharge starting voltage V
The relationship with _th is as shown in FIG. 6C according to Paschen's law. That is, when the gap is about 30 μm, the discharge starting voltage V _th is the smallest, and the gap is about 30 μm.
Regardless of whether it is smaller or larger than μm, the discharge starting voltage _Vth increases, and it becomes difficult for discharge to occur. This discharge also charges the surface of the image carrier 2. However, when the resistance R of the writing electrode 3 is in this region, the charge of the image carrier 2 due to charge injection is large, and the charge of the image carrier 2 due to discharge is small. Is dominant. In charging by the charge injection, the surface potential of the image carrier 2 becomes to the predetermined voltage V ₀ or the ground voltage V ₁ applied to the writing electrode 3b. In the case of charging by charge injection, it is desirable that the predetermined voltage V ₀ supplied to the writing electrode 3 b is set to be equal to or lower than a discharge starting voltage V _{th at which} a discharge occurs between the writing electrode 3 b and the image carrier 2.

In a region where the resistance R of the writing electrode 3b is larger, the charge of the image carrier 2 due to charge injection is small, and the charge of the image carrier 2 due to discharge becomes larger than the charge due to charge injection. In the charging of No. 2, charging by discharge gradually becomes dominant. That is, the resistance R of the write electrode 3b
Is larger, the surface of the image carrier 2 is charged mainly by electric discharge, and the image carrier 2 is hardly charged by charge injection. In or removal of charge by the discharge, the surface potential of the image carrier 2 becomes a voltage obtained by subtracting the discharge starting voltage V _th from the predetermined voltage V ₀ or ground voltages V ₁ is applied to the writing electrode 3b. The same applies to the case where the predetermined voltage V ₀ is a voltage of (+).

Therefore, the resistance R of the electrode 3b is changed
A predetermined voltage | V where the surface potential of the holder 2 is constant₀| (± voltage
Therefore, it is expressed as an absolute value) or a constant ground voltage V
₁And the write electrode 3b
Is a predetermined voltage V ₀And ground voltage V₁Between
Switching control enables image sharing by charge injection.
The holding body 2 can be charged.

The write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
Relationship between capacitance C of image carrier 2 and surface potential of image carrier 2
Represents a region where the capacitance C is small, as indicated by the solid line in FIG.
In the range, the surface potential of the image carrier 2 is constant at a predetermined voltage V₀Tona
In a region where the capacitance C is larger than a predetermined value,
The absolute value of the surface potential decreases. On the other hand, the write electrode 3b is set to B
Image bearing when this writing electrode 3b is grounded by connecting
The relationship between the capacitance C of the body 2 and the surface potential of the image carrier 2 is shown in FIG.
As shown by the dotted line in (D), the capacity C of the image carrier 2 is small.
In the region, the surface potential of the image carrier 2 is substantially constant and substantially equal to the ground voltage V.
₁Where the capacity C of the image carrier 2 is larger than a predetermined value.
Then, the absolute value of the surface potential of the image carrier 2 increases.

Then, in a region where the capacitance C of the image carrier 2 is small and the surface potential of the image carrier 2 is a constant predetermined voltage V ₀ or a constant ground voltage V ₁ , the writing electrode contacting the image carrier 2 Charge injection of (-) charges is performed directly between 3b and the charging layer 2d of the image carrier 2. That is, the image carrier 2 is charged by charge injection. In a region where the capacitance C of the image carrier 2 is large and the surface potential of the image carrier 2 starts to change, the charge of the image carrier 2 due to charge injection gradually decreases, and the capacitance C of the image carrier 2 decreases. As shown in FIG. 6B, the base material 3a and the image carrier 2
And a discharge is caused to occur between them. This discharge also charges the surface of the image carrier 2. However, when the capacity C of the image carrier is in this area, the charge of the image carrier 2 due to the charge injection is large and the charge of the image carrier 2 due to the discharge is small, and the charge of the image carrier 2 is dominated by the charge due to the charge injection. It has become a target. In charging by the charge injection, the surface potential of the image carrier 2 becomes to the predetermined voltage V ₀ or the ground voltage V ₁ applied to the writing electrode 3b.

In a region where the capacity C of the image carrier 2 is larger, the charge injection is hardly performed between the writing electrode 3b and the charged layer 2d of the image carrier 2. That is, the image carrier 2 is not charged by the charge injection. The same applies to the case where the predetermined voltage V ₀ is a voltage of (+).

Therefore, the capacitance C of the image carrier 2 is set to a small area where the surface potential of the image carrier 2 becomes a constant predetermined voltage | V ₀ | or a constant ground voltage V _1, and the writing electrode 3 b Is controlled between the predetermined voltage V ₀ and the ground voltage V ₁ to charge the image carrier 2 by charge injection.

Further, the write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
Velocity (peripheral speed) V of image carrier 2 and surface potential of image carrier 2
As shown by the solid line in FIG.
In a region where the velocity v of the image carrier 2 is relatively small,
The potential increases as the speed v increases, and the image bearing
When the speed v of the body 2 becomes larger than a predetermined value,
The absolute value of the surface potential is a constant voltage. Table of image carrier 2
The surface potential increases as the speed v of the image carrier 2 increases.
Shows an image caused by friction between the writing electrode 3b and the image carrier 2.
Facilitating charge injection by friction of the carrier 2
It is thought to be due to. Charge due to this friction
In order to facilitate the insertion, the speed v of the image carrier 2 is increased to some extent.
And does not change, and becomes almost constant. On the other hand, the write electrode 3b is
Speed when the write electrode 3b is connected to the B side and the write electrode 3b is grounded
The relationship between v and the surface potential is shown by the dotted line in FIG.
Constant ground voltage V regardless of speed v₁Becomes In addition,
Predetermined voltage V₀The same applies to the case where is a voltage of (+).

Further, the write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
The pressing force of the writing electrode 3b against the image carrier 2 (hereinafter simply referred to as writing
(Referred to as the pressure of the electrode 3b) and the surface potential of the image carrier 2.
The relationship is as shown by the solid line in FIG.
In a region where the force is extremely small, the surface potential of the image carrier 2 is
As the pressure of the writing electrode 3b increases, it becomes relatively sharp.
Rises, and the pressure of the writing electrode 3b becomes larger than a predetermined value.
And the absolute value of the surface potential of the image carrier 2 becomes a constant voltage.
You. The surface potential of the image carrier 2 increases the pressure of the writing electrode 3b.
Rise rapidly according to the writing electrode 3 b and the image carrier 2.
Contact becomes more reliable as the pressure of the write electrode 3b increases.
It is thought to be the result. This writing
The reliability of the contact between the electrode 3b and the image carrier 2 depends on the writing electrode 3
When the pressure of b becomes large to some extent, it does not change and is almost constant
Becomes On the other hand, by connecting the write electrode 3b to the B side,
Pressure and image bearing of writing electrode 3b when electrode 3b is grounded
The relationship with the surface potential of the body 2 is shown by the dotted line in FIG.
The constant ground voltage V is independent of the pressure of the write electrode 3b.₁
Becomes The predetermined voltage V₀Even if the voltage is (+)
The same is true.

In this manner, the resistance R of the writing electrode 3b and the capacitance C of the image carrier 2 are set so that the surface potential of the image carrier 2 becomes a constant predetermined voltage.
And the pressure of the writing electrode 3b are controlled so that the surface potential of the image carrier 2 becomes a constant predetermined voltage.
Switching control of the voltage applied to b between the predetermined voltage V ₀ and the ground voltage V ₁ makes it possible to reliably and easily charge the image carrier 2 by charge injection.

FIG. 7 is a view showing an example of an arrangement pattern when a plurality of write electrodes 3b are arranged in the axial direction of the image carrier 2. In FIG. The simplest arrangement pattern of the plurality of write electrodes 3b is, as shown in FIG.
b are arranged in a line in the axial direction of the image carrier 2. In this case, among the plurality of writing electrodes 3b, driving control by switching the writing electrodes 3b writing electrode 3b is their respective predetermined number (eight in the illustrated example) to a predetermined voltage V ₀ or ground voltages V ₁ Are connected to one driver 3c to be combined into one set.
Are arranged in a line in the axial direction.

However, when the write electrodes 3b are simply arranged in a line in the axial direction of the image carrier 2, crosstalk between adjacent write electrodes 3b may occur. Therefore, in the example shown in FIG. 7B, the writing electrodes 3b are arranged in two rows and in a zigzag manner in the direction orthogonal to the axial direction of the image carrier 2, and the row spacing of the writing electrodes 3b is increased. The crosstalk between the electrodes is reduced.

FIG. 8 is a diagram showing a switching circuit for switching and connecting predetermined voltage V ₀ and ground voltage V ₁ to write electrode 3b. As shown in FIG. 8, for example, the write electrodes 3b arranged in four rows are respectively connected to corresponding high voltage switches (HVSW) 15, and these high voltage switches 15 , to the corresponding electrode 3b and the predetermined voltage V ₀ and the ground voltages V ₁ is adapted to switch connection. An image writing control signal from a shift register (S.R.) 16 is input to each of the high voltage switches 15.
To 6, the image signal stored in the buffer 17 and the clock signal from the clock 18 are input. Then, the image write control signal from the shift register 16 is input to each high voltage switch 15 by the AND circuit 19 based on the write timing signal from the encoder 20. The above-mentioned driver 3c for controlling the switching of the supply voltage to each writing electrode 3b by each high voltage switch 15 and AND circuit 19 is configured.

FIG. 9 shows each high voltage switch 15 of each electrode 3b.
FIG. 9A is a diagram for explaining a state when each is selectively switched to a predetermined voltage V ₀ or a ground voltage V ₁ , and FIG. 9A shows a voltage state of each electrode;
9B is a diagram showing a developer image when normal development is performed in the voltage state of FIG. 9A, and FIG. 9C is a diagram showing a developer image when reverse development is performed in the voltage state of FIG. 9A. FIG.

For example, as shown in FIG.
-1st, nth, n + 1th, n + 2th electrodes 3
In FIG. 9B, it is assumed that the respective high-voltage switches 15 are switched and controlled to be in the voltage state shown in FIG. 9A. Therefore, when the electrostatic latent image is written on the latent image carrier 2 by each electrode in such a voltage state and the electrostatic latent image is developed by regular development, the developer 8 Predetermined voltage V
_The developer image adheres to the ₀ portion, and a developer image as shown by hatching in FIG. 9B is obtained. Further, performs writing of an electrostatic latent image in the same manner, when developing the electrostatic latent image by reversal development, the developer 8 is deposited on the ground voltages V ₁ part of the latent image carrier 2, FIG. 9 ( A developer image as shown by hatching in C) is obtained.

According to the image forming apparatus 1 using the writing device 3 configured as described above, the writing electrode 3b is brought into contact with the latent image carrier 2 with a small pressing force due to the small elastic restoring force of the base material 3a. Therefore, the writing electrode 3b can be stably brought into contact with the latent image carrier 2. Therefore, the latent image carrier 2 can be more stably and highly accurately charged by the writing electrode 3b. Thereby, the writing of the electrostatic latent image can be performed more stably, so that a good image can be obtained reliably and with high accuracy.

Also, since the writing electrode 3b is only brought into contact with the latent image carrier 2 with a small pressing force, the writing electrode 3b
Can prevent the latent image carrier 2 from being damaged, and the durability of the latent image carrier 2 can be improved. Furthermore, since only the writing electrode 3b is used as the writing device 3 and a large laser light generating device or an LED lamp light generating device as in the related art is not provided, the size of the device can be further reduced. As a result, the number of parts can be further reduced, and a simpler and less expensive image forming apparatus can be obtained. Further, generation of ozone can be further suppressed by the writing electrode 3b.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made. For example, although a cleaning blade is used as the cleaning means, a cleaning brush, a cleaning roller, or other means may be used. According to the present invention, it is possible to prevent the toner leaking from the end of the cleaning means for removing the residual toner from adhering from the image carrier to the contact portion between the writing electrode and the image carrier via the lower surface of the base of the writing device. It is not limited to the cleaning unit for removing the residual toner on the intermediate transfer belt as in the above-described embodiment.
The same applies to the cleaning means for removing the residual toner on the recording medium transport belt and other cleaning means.

The same applies to black-and-white, mono-color, and full-color image forming apparatuses. In a full-color image forming apparatus, a rotary type in which developing devices of each color are arranged around an image carrier, and each color is formed on a belt. The same applies to any tandem type in which the developing device is disposed. Of these, a specific example of a tandem-type full-color image forming apparatus using the writing device of the present invention for writing an electrostatic latent image by bringing the electrode portion 3b into contact with the image carrier 2 will be described below. FIG. 10 schematically shows an example of a tandem-type full-color image forming apparatus in which a cleaning unit for removing the residual toner on the conveyance belt is arranged. FIG. 11 shows a cleaning unit for removing the residual toner on the intermediate transfer belt. It is a diagram schematically showing an example of a tandem type full-color image forming apparatus,
5 'is a recording medium transport belt, 21 is a paper tray, 22 is a registration roller, 23 is a transfer device, and 24 is a fixing device.

First, an image forming apparatus for forming a full-color image by directly superimposing toner images of respective colors on a recording sheet sequentially and transferring them will be described. Image forming apparatus 1 of example shown in FIG.
Means that the image forming apparatus 1 for each color uses the recording medium transport belt 5 '.
Are arranged in tandem in the order of yellow Y, magenta M, cyan C, and black BK from the upstream side in the moving direction of the recording sheet 5a conveyed by. The arrangement order of the image forming apparatuses 1 for each color can be set in any order. Each image forming apparatus 1 includes an image carrier 2, a writing device 3, a developing device 4, and a transfer device 6.

In the image forming apparatus 1 configured as described above, first, in the yellow Y image forming apparatus 1,
The electrostatic latent image of yellow Y is written on the surface of the image carrier 2 by the electrode 3 b of the writing device 3, and the electrostatic latent image of yellow Y is developed by the developing device 4 to be applied to the surface of the image carrier 2. A yellow Y toner image is formed. The transfer device 6 transfers the yellow Y toner image on the image carrier 2 to the paper tray 2.
The toner image is transferred onto the recording sheet 5a conveyed from No. 1 and a yellow Y toner image is formed on the recording sheet 5a.

Next, in the magenta M image forming apparatus 1, an electrostatic latent image of magenta M is written on the surface of the image carrier 2 by the electrode 3b of the writing device 3, and the electrostatic latent image of magenta M is written. The toner is developed by the developing device 4 and a magenta M toner image is formed on the surface of the image carrier 2. The transfer device 6 transfers the magenta M toner image on the image carrier 2 onto the recording sheet 5a on which the conveyed yellow Y toner image is formed, and transfers the magenta M toner image onto the recording sheet 5a. It is formed.

Similarly, in the cyan C image forming apparatus 1, the electrostatic latent image of cyan C is written on the image carrier 2 by the electrode 3 b of the writing device 3 and the electrostatic latent image of the developing device 4 is formed. After the development and the superimposition transfer of the cyan C toner image onto the recording sheet 5a of the transfer device 6, the black BK is applied to the image carrier 2 by the electrode 3b of the writing device 3 in the black BK image forming apparatus 1. Writing and developing device 4 for electrostatic latent image
Of the electrostatic latent image of the recording device 5a of the transfer device 6
The black BK toner image is transferred to the recording sheet 5a to form a full-color toner image in which the toner images of each color are color-matched.

The cleaning blade 11 is provided for the purpose of erasing alignment marks and the like of each color formed on the recording medium transport belt 5 '. If it wraps around from 5 'to the contact portion between the writing device 3 and the image carrier 2 and adheres unevenly, the contact pressure between the writing device 3 and the image carrier 2 fluctuates and the writing electrode 3b is contaminated. By
The formation of a latent image is hindered, and image unevenness occurs.

In the image forming apparatus to which the present invention is applied, the width of the cleaning blade 11 abutting on the recording medium transport belt 5 'is set to be equal to the width of the image of each color, as in the embodiment shown in FIG. Image carrier 2 of forming apparatus 1
And the width of the image carrier 2 is increased
Is larger than the width in contact with the image carrier 2. As a result, the toner leaking from the edge of the cleaning blade 11 does not adhere to the image carrier 2, and therefore, the toner leaking from the edge at the contact portion between the writing device 3 and the image carrier 2 via the image carrier 2. As a result, it is possible to prevent sneaking around and adhere, and the above-described obstructive factors of latent image formation are eliminated.

As described above, even in a full-color image forming apparatus in which the image forming apparatuses 1 of each color are arranged in tandem,
By using the writing device 3 of the present invention, the configuration can be made smaller and simpler, and the contact width of the cleaning blade 11 with the recording medium transport belt 5 ′ is larger than the width of the image carrier 2. By making the width of the image carrier 2 larger than the contact width of the image carrier 2 of the writing device 3, the end leakage toner adheres to the contact portion between the writing electrode and the image carrier. It is possible to prevent the gap between the writing electrode and the image carrier from fluctuating, thereby preventing image unevenness.

In the image forming apparatus 1 of the example shown in FIG. 10 in which the image forming apparatuses 1 of the respective colors are arranged in tandem, the toner images of the respective colors formed on the image carrier 2 of the respective image forming apparatuses 1 are used. Each image is transferred to a recording sheet 5a conveyed by a recording medium conveying belt 5 '. However, in the image forming apparatus 1 of the example shown in FIG. After the toner images of each color are once transferred to the intermediate transfer belt 5, they are transferred to the recording sheet 5a. That is, in the image forming apparatus 1 of the example shown in FIG. 11, the intermediate transfer belt 5 is provided in the image forming apparatus 1 of the example shown in FIG. The intermediate transfer belt 5 is an endless belt-shaped intermediate transfer member, and includes two rollers 12 and 1.
3 and is rotated counterclockwise in the figure by driving one of the rollers 12.

Each image forming apparatus 1 is disposed along the linear portion of the intermediate transfer belt 5, and one secondary transfer device 23 is provided at the position of the roller 13. Another configuration of the image forming apparatus 1 of this example is shown in FIG.
0 is the same as the image forming apparatus 1 of the example shown in FIG.

In the thus formed image forming apparatus 1 of this example, similarly to the image forming apparatus 1 of the example shown in FIG. 10, a toner image of each color is formed on the image carrier 2 of each color. The toner images of each color are transferred onto the intermediate transfer belt 5,
In the same manner as in the case of transferring to the recording sheet 5a in the example shown in FIG. The toner image of each color intermediately transferred to the intermediate transfer belt 5 is transferred to the recording sheet 5a by the secondary transfer device 23, and a full-color toner image is formed on the recording sheet 5a. Another image forming operation of the image forming apparatus 1 of this example is shown in FIG.
0 is the same as the image forming apparatus 1 of the example shown in FIG.

The cleaning blade 11 removes the toner remaining on the secondary transfer device 23 after the transfer, and the toner leaking from the end of the cleaning blade 11 is transferred from the intermediate transfer belt 5 to the writing device 3 and the image forming device. If it wraps around the contact portion of the carrier 2 and adheres non-uniformly, the contact pressure between the writing device 3 and the image carrier 2 fluctuates and the writing electrode 3b is contaminated, thereby obstructing the formation of a latent image and causing an image. Unevenness occurs.

In the image forming apparatus to which the present invention is applied, in order to eliminate this obstructive factor, similarly to the embodiment shown in FIG. 1, the writing device width L3 at which the writing device 3 comes into contact with the image carrier 2 is used.
In contrast, the width L2 of the image carrier 2 is increased, and the cleaning blade 11 contacts the intermediate transfer belt 5 with a cleaning blade width L1 larger than the width L2 of the image carrier 2.
Increase 1 As a result, toner leaking from the end of the cleaning blade 11 adheres to the end of the image carrier 2,
The end leakage toner can be prevented from sneaking into and abutting on the contact portion between the writing device 3 and the image carrier 2, and the above-described obstruction to the latent image formation can be eliminated.

As described above, even in a full-color image forming apparatus having the intermediate transfer belt 5 and the image forming apparatuses 1 of each color arranged in tandem, by using the writing device 3 of the present invention, it is possible to reduce the size and size. The intermediate transfer belt 5 of the cleaning blade 11 can have a simpler configuration.
The width of the image carrier 2 is made larger than the width of the image carrier 2, and the width of the image carrier 2 is made larger than the width of the contact of the writing device 3 with the image carrier 2. The writing electrode and the image carrier 2 are attached to the contact portion between the write electrode and the image carrier.
Can be prevented from fluctuating and causing image unevenness.

Needless to say, the black-and-white image forming apparatus, the mono-color image forming apparatus, and the rotary type full-color image forming apparatus can be made smaller and simpler by using the writing device of the present invention. In the same manner as described above, the contact width of the cleaning blade is made larger than the contact width of the image carrier of the writing device, so that the toner leaking from the edge adheres to the contact portion between the writing electrode and the image carrier. Needless to say, it is possible to prevent the gap between the input electrode and the image carrier from fluctuating, thereby causing image unevenness.

In the illustrated example, the writing device 3 and the developing device 4 are arranged in the order of Y, M, C, and BK from the upstream side in the rotation direction of the image carrier 2 along the linear portion of the endless belt. However, it goes without saying that these developing devices 4 can be arranged in any order other than that shown. Each electrode 3b of each color writing device 3 is lightly in contact with the image carrier 2 with a small pressing force as described above. In the image forming apparatus 1 of this example, after the surface of the image carrier 2 is uniformly charged by the image carrier uniform charging control device, writing is performed by the writing device 3. No charge control device,
The writing device 3 may be configured to perform writing.

[0062]

As is apparent from the above description, according to the present invention, the toner image developed on the image carrier is primarily transferred to the intermediate transfer member, and the toner image on the intermediate transfer member is transferred to the recording medium. Writing means for forming an electrostatic latent image on an image carrier having a plurality of write electrodes arranged in contact with or close to the image carrier along the axial direction of the image carrier; Cleaning means for abutting the transfer member to remove residual toner, wherein the width of the image carrier is at least larger than the width of the writing means, and the width of contact of the cleaning means with the intermediate transfer member is greater than the width of the image carrier. In an image forming apparatus for transferring a toner image developed on an image carrier to a recording medium conveyed by a recording medium conveying unit, the image forming apparatus is in contact with or close to the image carrier along the axial direction of the image carrier. Multiple write electrodes A writing unit that forms an electrostatic latent image on the image carrier; and a cleaning unit that abuts on the recording medium transport unit and removes residual toner, wherein the width of the image carrier is larger than at least the width of the writing unit. In addition, the contact width of the cleaning unit with the recording medium conveying unit is larger than the width of the image carrier, so that even if toner is removed by the cleaning unit, the end leakage toner remaining on the recording medium conveying unit or on the intermediate transfer member. Can be prevented from adhering to the image carrier, and the toner leaking from the end of the cleaning means via the image carrier to the contact portion between the writing means and the image carrier to adhere unevenly, thereby forming a latent image. Can be prevented. Therefore, the contact between the writing means and the image carrier is stabilized, uniform selective writing becomes possible, and a good image without image unevenness or streaks can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view showing an embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a diagram illustrating an example of a case where toner leaking from an end adheres and accumulates on a writing device via an intermediate transfer belt and an image carrier.

FIG. 4 is a diagram for explaining generation of toner leaking from an end seal.

FIG. 5 is a diagram for explaining the principle of writing an electrostatic latent image by charging a writing electrode of a writing device.

FIG. 6 is a diagram for explaining the principle of writing an electrostatic latent image by charging a writing electrode of a writing device.

FIG. 7 is a diagram showing an example of an arrangement pattern when a plurality of write electrodes are arranged in an axial direction of an image carrier.

FIG. 8 shows that a predetermined voltage V ₀ and a ground voltage V _{1 are} applied to the write electrode
FIG. 3 is a diagram showing a switching circuit for switching connection of the switching circuit.

9 is a diagram for explaining a state when selectively switching controls each high voltage switch for each electrode in each predetermined voltage V ₀ or the ground voltage V _1.

FIG. 10 is a diagram schematically illustrating an example of a tandem-type full-color image forming apparatus provided with a cleaning unit that removes residual toner on a conveyance belt.

FIG. 11 is a diagram schematically illustrating an example of a tandem-type full-color image forming apparatus provided with a cleaning unit that removes residual toner on an intermediate transfer belt.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image carrier, 3 ... Writing apparatus, 3a
... Substrate, 3b ... writing electrode, 3c ... driver, 3d ... conductive pattern, 4 ... developing device, 5 ... intermediate transfer belt, 6 ... transfer roller, 7, 11 ... cleaning blade, 12, 1
3: belt support roller, L2: image carrier width, L3: writing device width, L11: cleaning blade width

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Kazuo Yoda, 3-3-5, Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor, Yujiro Nomura 3-5-2, Yamato, Suwa-shi, Nagano, Seiko-Epson (72) Inventor Shinichi Kamoshida 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation F-term (reference) 2C162 AE21 AE44 AE47 AE92 EA20 2H029 AA06 AB03 AB10 AB12 AD07 AE01 2H032 AA15 BA01 BA09 BA23 BA30 2H034 AA06 BA02 BD01

Claims (2)

[Claims] 1. An image forming apparatus which primarily transfers a toner image developed on an image carrier to an intermediate transfer member and transfers the toner image of the intermediate transfer member to a recording medium, along an axial direction of the image carrier. Writing means for forming an electrostatic latent image on the image carrier having a plurality of writing electrodes in contact with or close to the image carrier, and removing residual toner by contacting the intermediate transfer member Cleaning means, wherein the width of the image carrier is at least larger than the width of the writing means, and the contact width of the cleaning means with the intermediate transfer member is larger than the width of the image carrier. Image forming apparatus. 2. An image forming apparatus for transferring a toner image developed on an image carrier to a recording medium conveyed by a recording medium conveying means, wherein said toner image contacts or approaches the image carrier along an axial direction of said image carrier. A writing unit having a plurality of writing electrodes disposed thereon and forming an electrostatic latent image on the image carrier; and a cleaning unit abutting on the recording medium transporting unit and removing residual toner, wherein at least the An image forming apparatus, wherein the width of the image carrier is larger than the width of a writing unit, and the contact width of the cleaning unit with the recording medium conveying unit is larger than the width of the image carrier.