JP3348128B2 - Image forming device - Google Patents

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 by a wet electrophotographic process applied to a copying machine, a digital copying machine, a laser printer, a facsimile and the like.

[0002]

2. Description of the Related Art In an image forming apparatus by a wet electrophotographic process for obtaining an image by transferring an image formed on a photosensitive drum to a transfer paper using a developing solution, a general method of separating the transfer paper from the photosensitive drum is used. The method is a method of mechanically forcibly separating using a separation blade or a belt. But,
This apparatus has a disadvantage that an image cannot be formed on the entire surface of the transfer paper. Therefore, as an apparatus for solving the problem, there is an apparatus using a transfer belt for electrostatically adsorbing and transferring a transfer sheet.

Further, in an image forming apparatus using a dry electrophotographic process, transfer paper is sequentially transferred to each transfer position formed by arranging photosensitive members corresponding to a plurality of different colors at regular intervals on the same plane. 2. Description of the Related Art In a color image forming apparatus which sequentially transfers toner images of respective colors by transporting, there is an apparatus using a transfer belt.

Accordingly, even in an image forming apparatus using a wet electrophotographic process, a color image forming method using a transfer belt is applied by applying the color image forming method in a color image forming apparatus using a dry electrophotographic process using a transfer belt. Forming the forming device is easy.

[0005]

However, in an image forming apparatus based on a wet electrophotographic process using a transfer belt, even if transfer paper does not exist in a transfer nip formed at a contact point between the photosensitive drum and the transfer belt. Regardless, when the developing solution is supplied, there is a problem that the developing solution (a carrier liquid such as an isopar) accumulates in a meniscus shape in the transfer nip portion, soiling the transfer paper and adversely affecting the image.

Further, considering a jam due to transfer paper of the image forming apparatus, a developing solution may be supplied to the transfer nip when a transfer paper does not exist in the transfer nip. There is a problem that the drum and the transfer belt need to be separated, and a device for that purpose is complicated.

Further, in a color image forming apparatus using a transfer belt, there is a problem that color mixing occurs via the transfer belt.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In an image forming apparatus by a wet electrophotographic process using a transfer belt, a developing solution is prevented from accumulating in a transfer nip. Get the image,
An object of a color image forming apparatus is to reduce color mixture generated via a transfer belt.

[0009]

According to the present invention, an image carrier for holding and transporting a developer for forming an image is provided opposite to a carrier for holding and transporting a transfer medium,
In the image forming apparatus to form a transfer nip for transferring an image on the image bearing member to a transfer medium on the carrier, prior to
Selectively supplying developer regulating means the developer to serial transfer nip, the transfer medium on the conveying member is the transfer two
Transfer medium detection for detecting the transfer medium before reaching the
And a bias power supply.
And an electrode member for applying the
And the transfer medium is transferred to the transfer medium detecting means.
The bias power supply by the electrode member
To stop the application of
It was formed by the as power supply control means .

[0010]

[0011]

[0012]

[0013]

According to a second aspect of the present invention, a plurality of image carriers for holding and transporting a developer for forming an image are provided opposite to a carrier for holding and transporting the transfer medium, and the plurality of image carriers are provided. In an image forming apparatus formed with a plurality of transfer nips for transferring the upper image to the same transfer medium on the carrier, a developer adjusting means for selectively supplying the developer to the transfer nip, a transfer medium detecting means for detecting the transfer medium prior to the transfer medium on the carrier reaches the transfer nip portion, the transfer medium on the conveying member is the rolling
A transfer medium for detecting the transfer medium before reaching the photo nip portion
Body detecting means provided for each image carrier , and the developer adjusting means
An electrode member for applying a bias power;
The power supply is controlled according to the sequence so that the transfer medium
When detected by the recording medium detection means,
When the application of the bias power is stopped and the detection is
It is formed by the bias power supply control means which is sometimes restarted .

[0015]

According to the first aspect of the present invention, since the developer is selectively supplied to the transfer nip by the developer adjusting means, the developer is supplied even though there is no transfer paper in the transfer nip. The developer can be prevented from accumulating in the transfer nip portion, thereby making it possible to obtain a good image without separating the image carrier and the carrier when a jam occurs, In the color image forming apparatus, it is possible to reduce the color mixture generated via the conveyance body . In addition, the bias power supply control means
Controlling the applied bias power according to the sequence
The developer is applied to the transfer nip by the electrode member.
Transfer paper is present in the transfer nip to selectively supply
The developer will not be supplied
Therefore, it is possible to prevent the developer from accumulating in the transfer nip.
This allows the image carrier and carrier to be separated when a jam occurs.
Good image easily by electrical control without releasing
Images, and a color image forming apparatus.
Can reduce the color mixing that occurs through the carrier.
Becomes Further, the transfer medium detecting means detects that the transfer medium
Body before it reaches the transfer nip,
The step allows the developer to be selectively supplied to the transfer nip.
Therefore, even though there is no transfer paper in the transfer nip,
The developer is no longer supplied and the developer is transferred
Can be prevented from accumulating in the
Ensure that the image carrier and carrier are not separated when they occur.
Good images can be obtained, and color images
In the image forming apparatus, it is necessary to reduce the color mixture generated through the conveyance body.
It becomes possible .

[0016]

[0017]

[0018]

[0019]

According to the second aspect of the invention, the transfer medium detecting means provided for each image carrier detects the transfer medium on the carrier before reaching each transfer nip portion, and responds according to the information. Since the developer adjusting means selectively supplies the developer to each transfer nip portion, the developer is not supplied even though there is no transfer paper in the transfer nip portion. This makes it possible to reliably collect a good image without separating the image carrier and the carrier in the event of a paper jam. It is possible to reduce the color mixing that occurs through the system, and it is not necessary to provide a jam counter in the sequence. Can further reduce the color mixture occurs through become. Also, the bias power supply control means
Controls bias power applied to members according to sequence
By doing so, the transfer nip portion is
Transfer to the transfer nip to selectively supply developer to the
Developer supplied without paper
To prevent the developer from accumulating in the transfer nip.
This allows the image carrier to be transported when a paper jam occurs.
Easy to control by electrical control without separating the body
A good image can be obtained, and a color image
In the forming equipment, reduce the color mixture generated through the carrier
Becomes possible. Further, the transfer medium detecting means
The transfer medium is detected before reaching the transfer nip, and the developer
Selective supply of developer to transfer nip by adjusting means
If there is no transfer paper in the transfer nip,
And no developer is supplied.
It is possible to prevent accumulation in the transfer nip part,
When the jam occurs, the image carrier and carrier are not separated
A good image can be obtained without fail, and
Color mixing that occurs via the carrier in the color image forming apparatus
It is possible to do .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a partial vertical side view of the color image forming apparatus, and FIG. 2 is a vertical side view of the color image forming apparatus. FIG. 3 is a time chart of the color image forming apparatus. In FIG. 1, a transfer nip portion 3 is formed at a contact point between a photosensitive drum 1 as an image carrier and a transfer belt 2 as a carrier. A cleaning blade 4, a discharge lamp 5, a charging charger 6, and a developing casing 7 are sequentially held along the rotation direction of the photoconductor drum 1, and a space between the charging charger 6 and the developing casing 7 is provided. An exposure unit 8 is formed in the image forming apparatus, and a transfer nip 3 is formed between the developing casing 7 and the cleaning blade 4. Inside the developing casing 7, a developing device 9, a reverse roller 10, and a bias roller 11 are sequentially held as electrode members along the rotation direction of the photosensitive drum 1, and outside the transfer belt 2. The transfer paper detection sensor 12 is held as a transfer medium detection unit in opposition to the image forming apparatus. The transfer charger 13 is held opposite the transfer nip portion 3. Further, although not shown, a bias power control means for the bias roller 11 is provided. The bias roller 11 and the bias power control means form a developer adjusting means.

The photosensitive drum 1 is rotating at a constant speed in the direction of transfer of the transfer paper. And the charging charger 6
Thereby, the surface potential is uniformly charged to about +600 V. Thereafter, the surface is exposed by the laser beam 26 from the exposure device in the exposure unit 8 to lower the surface potential, and an electrostatic latent image is formed on the surface. For example, the surface potential at this time is approximately +50 V at the exposed portion.
And the unexposed portion remains unchanged at about + 600V. Then, the electrostatic latent image is developed by the developing device 9 to become a visible image by the developer. Since a developing bias of about +160 V is applied to the developing roller 22 of the developing device 9, the developing solution adheres to the high-potential portion of the photosensitive drum 1 which has not been exposed in the exposing section 8, and is exposed. This is because the developing solution does not adhere to the low potential portion and the developing solution adheres to the intermediate potential portion at a density corresponding to the surface potential.

The bias power supply control means is means for controlling a bias applied to the bias roller 11 in accordance with information from the transfer paper detection sensor 12, and when the transfer paper detection sensor 12 does not detect the transfer paper. The bias is applied to the bias roller 11 so that the bias is not applied to the bias roller 11 when the transfer paper detection sensor 12 detects the transfer paper.

The bias roller 11 rotates in a circumferential direction with respect to the rotation direction of the photosensitive drum 1, and transfers the visible image on the photosensitive drum 1 to the transfer nip 3 even though the visible image on the photosensitive drum 1 is being conveyed. When the transfer paper on the transfer belt 2 is not being conveyed to the nip 3, the bias is applied by the bias power supply control means to squeeze the developer on the photosensitive drum 1. Further, a rubber blade 27 is in contact with the bias roller 11. The rubber blade 27 is a mechanism for cleaning the surface of the bias roller 11, and instead of the rubber blade 27, a metal scraper or the like that is in contact with the surface to clean the surface is used.

In the transfer nip section 3, the visible image on the photosensitive drum 1 and the transfer paper on the transfer belt 2 are simultaneously supplied, and the visible image is transferred to the transfer paper.

Furthermore, in FIG. 2, four photosensitive drums 1 are provided for color image formation in the overall configuration. The periphery of each photosensitive drum 1 has the same structure as the structure described in FIG. The four photosensitive drums 1 are a photosensitive drum for black (hereinafter, referred to as photosensitive drum BK) 1a, a photosensitive drum for magenta (hereinafter, photosensitive drum M) 1b, and a photosensitive drum for yellow. Body drum (hereinafter, referred to as photosensitive drum Y) 1
c, a photosensitive drum 1d for cyan (hereinafter, referred to as photosensitive drum C) 1d is arranged on the same plane at regular intervals. The transfer belt 2 is supported by a driving roller 14 and a driven roller 15, and is stretched so as to be in contact with the four photosensitive drums 1a, 1b, 1c and 1d. Then, the four photosensitive drums 1a, 1b,
A bias roller 11 and a transfer paper detection sensor 12 are provided for each of 1c and 1d. That is, although not shown in FIG. 2, a black bias roller (hereinafter, referred to as a bias roller BK) and a black transfer paper detection sensor (hereinafter, transfer paper detection) are provided for the photosensitive drum BK1a. A sensor BK), a magenta bias roller (hereinafter, referred to as a bias roller M) and a magenta transfer paper detection sensor (hereinafter, referred to as a transfer paper detection sensor M) for the photosensitive drum M1b. ) Is a yellow bias roller (hereinafter, referred to as a bias roller Y) for the photosensitive drum Y1c.
And a transfer paper detection sensor for yellow (hereinafter, referred to as a transfer paper detection sensor Y), for the photosensitive drum C1d, a bias roller for cyan (hereinafter, referred to as a bias roller C), and a transfer roller for cyan. Transfer paper detection sensor
Transfer paper detection sensor C). A registration roller 16 is disposed below the transfer belt 2, and a fixing roller 17 and a press roller 18 are disposed above the registration roller 16.
And are arranged. The fixing roller 16 and the press roller 17 are in contact with each other. The optical exposure device 19 for forming an electrostatic latent image on the surface of each of the four photosensitive drums 1a, 1b, 1c, and 1d includes the photosensitive drum 1a,
1b, 1c, and 1d. further,
Although not shown, a print key is provided.

The transfer belt 2 is connected to the drive roller 14
The four photosensitive drums 1a, 1b, 1c, 1
Rotating at the same speed as d, the transfer paper 20 as a transfer medium is transported from the registration roller 18 side to the fixing roller 16 side through four transfer nip portions. Further, the transfer belt 2 is configured such that the transfer paper 20 is
Before being supplied by the cleaning blade 21. As a method for cleaning the transfer belt 2, the cleaning blade 2
There is also a method of wiping with synthetic leather or the like without using 1.

The photosensitive drums 1a, 1b, 1c, 1d
The surface is exposed by the laser beam 26 from the exposure device 19 to lower the surface potential, and an electrostatic latent image is formed on the surface.

A polygon motor 23 is held in the exposure device 19, and a polygon mirror 24 is attached to the polygon motor 23. A surface tilt correction lens 25 is held in the same plane as the polygon mirror 24. The polygon mirror 24 is rotated by the polygon motor 23, and reflects a laser beam 26 emitted from a semiconductor laser (not shown). The reflected laser beam 26 is reflected by a plurality of mirrors provided in the exposure device 19 to expose the photosensitive drum 1 to light. At this time, the laser light 26 is modulated based on the image signal, and the photosensitive drum BK1a is irradiated with the black laser light 26a, the photosensitive drum M1b is irradiated with the magenta laser light 26b, and the photosensitive drum Y1c is irradiated with the yellow laser light. 26c, the photosensitive drum C1
d is exposed by a cyan laser beam 26d.

In the transfer nip 3, the visible images on the four photosensitive drums 1a, 1b, 1c and 1d and the transfer paper 20 on the transfer belt 2 are simultaneously supplied, and the transfer paper 20 The visible image is transferred to the image. Then, the transfer paper 20
Passes through the transfer nips 3 formed for each of the four photosensitive drums 1a, 1b, 1c and 1d arranged on the same plane at regular intervals, the transfer nips 3
Photosensitive drums 1a, 1b, 1c, 1d conveyed each time
Each visible image is transferred, and a color image is obtained.

In such a configuration, based on FIG. 3, four bias rollers BK, M, Y, and C, four transfer paper detection sensors BK, M, Y, and C, a registration roller 18, Four photosensitive drums 1a, 1b, 1c, 1d,
The operation of the print key will be described. First, when the print key is pressed, four photosensitive drums 1
a, 1b, 1c, 1d, a registration roller 18, and
The four bias rollers BK, M, Y, and C are turned on, and the operation starts. Then, four photosensitive drums 1
a, 1b, 1c, and 1d continue to operate until the printing operation is completed.

However, the registration roller 18 transfers the transfer paper 2
When 0 is conveyed to the registration roller 18, the operation is temporarily stopped and the four photosensitive drums 1a, 1b, 1c, 1
The transfer paper 20 is supplied onto the transfer belt 2 such that the transfer paper 20 on the transfer belt 2 is transported at the timing when the visible image on the transfer belt 2 is transported to each transfer nip portion 3. When the transfer paper 20 is conveyed at a constant speed by the transfer belt 2 and is detected by the transfer paper detection sensor BK, the bias roller BK is turned off and the operation is stopped. This state is continued until the transfer paper detection sensor BK does not detect the transfer paper.
K resumes operation.

Thereafter, the photosensitive drums 1a, 1b, 1c,
Since the transfer papers 1d are arranged at regular intervals and the transfer belt 2 is driven at a constant speed, after the transfer paper detection sensor BK detects the transfer paper 20, the transfer paper detection sensor M The paper detection sensor Y and the transfer paper detection sensor C detect the transfer paper 20. When the transfer paper detection sensor M detects the transfer paper 20, as in the case of the transfer paper detection sensor BK and the bias roller BK described above, the bias roller M stops operating, and the transfer paper detection sensor Y
When 0 is detected, the bias roller Y stops operating, and when the transfer paper detection sensor C detects the transfer paper 20, the bias roller C stops operating.

This state continues for the same time as that of the above-described transfer paper detection sensor BK and bias roller BK, and also at regular intervals, the transfer paper detection sensor M, the transfer paper detection sensor Y, and the transfer paper The detection sensor C stops detecting the transfer paper 20. Then, the above-described transfer paper detection sensor BK
When the transfer paper detection sensor M stops detecting the transfer paper 20 as in the case of
Resumes operation, and when the transfer paper detection sensor Y stops detecting the transfer paper 20, the bias roller Y restarts operation. When the transfer paper detection sensor C stops detecting the transfer paper 20, the bias roller C operates. Resume.

Thereafter, the registration roller 18, the four bias rollers BK, M, Y, and C, and the four transfer paper detection sensors BK, M, Y, and C continue to operate until the printing operation is completed. To stop. As a result, the developing solution is supplied from the developing device 9 to the photosensitive drums 1a, 1b, 1c, and 1d to wet the photosensitive drums 1a, 1b, 1c, and 1d, but the transfer paper 20 is conveyed to the transfer nip portion 3. When there is no developer, the bias rollers BK, M, Y, and C electrically squeeze the developer on the photosensitive drums 1a, 1b, 1c, and 1d, so that the developer does not accumulate in the transfer nip portion 3.

As described above, each of the photosensitive drums 1a, 1b,
Transfer paper detection sensors BK, M, Y, and C are provided for each of the photosensitive drums 1a, 1b, 1c, and 1d to determine whether or not the transfer paper 20 is being conveyed to the corresponding transfer nip unit 3 for each of the photosensitive drums 1a, 1b, 1c, and 1d. Is detected, and the bias roller BK,
Depending on M, Y, C, the photosensitive drums 1a, 1b, 1c,
Since the visible image on 1d can be electrically squeezed to prevent the developer from collecting in the transfer nip portion 3, the photosensitive drums 1a, 1b, 1c, and 1d are separated from the transfer belt 2 when a jam occurs. A good image can be easily obtained by electrical control without the need to provide a jam counter in the sequence. In addition, since the jam monitoring becomes more severe, It is possible to further reduce the resulting color mixture.

Although not shown, a registration detection sensor is provided below the registration roller 16 in place of the transfer paper detection sensor 12 in this embodiment, and a discharge detection sensor is provided for the fixing roller 29. The CPU receives signals from the detection sensor and the registration detection sensor and detects the occurrence of a jam. By applying a conventional sequence control for detecting the occurrence of a jam using the paper ejection detection sensor, the registration detection sensor, and the CPU, it is possible to obtain a good image and further reduce the color mixture generated via the transfer belt 2. It is possible to reduce. The method counts the time from when the registration detection sensor detects the transfer paper 20 by the CPU to when the discharge detection sensor detects the transfer paper 20, and a predetermined time after the registration detection sensor detects the transfer paper 20. Even after the lapse of the above, the paper ejection detection sensor is
In the sequence control in which the CPU determines that a jam has occurred when no jam has been detected, the photosensitive drum 1 is controlled by the bias power control means and the bias roller when the jam occurs.
This is a method of electrically squeezing the developer on a, 1b, 1c and 1d.

Another embodiment will be described with reference to FIG.
Real施例same parts described with reference to FIGS. 1 to 3 using the same reference numerals, and a description thereof will be omitted. FIG. 4 is a partial longitudinal side view of the image forming apparatus. In place of the bias roller 11 shown in the above-described embodiment, a rubber blade 28 is held on the shaft 29 as a developing solution adjusting means so as to be able to contact and separate from the photosensitive drum 1 by a driving means such as a solenoid. Also,
Although not shown, a developer removing means is provided. The developer removing control means and the rubber blade 28 form a developer adjusting means.

The developer removal control means controls the contact and separation of the rubber blade 28 with the photosensitive drum 1 in accordance with information from the transfer paper detection sensor 12. Is not detected, the rubber blade 28 is brought into contact with the photosensitive drum 1,
When the transfer paper detection sensor 12 is detecting the transfer paper 20, the rubber blade 28 is controlled to be separated from the photosensitive drum 1.

The rubber blade 28 is mounted on the photosensitive drum 1
When the transfer paper 20 on the transfer belt 2 is not conveyed even though the visible image on the photosensitive drum 1 is conveyed to the transfer nip 3, the developing The developer on the photosensitive drum 1 is squeezed by being brought into contact with the photosensitive drum 1 by the liquid removal control means.

In such a configuration, at the same time as the printing operation is started, the rubber blade 28 is
Contact. The transfer paper detection sensor 12 detects whether or not the transfer paper 20 is being conveyed to the transfer nip portion 3. When the transfer paper 20 is being conveyed to the transfer nip portion 3, the rubber blade 28 is moved to the photosensitive drum. 1 and the transfer paper 20 is not conveyed to the transfer nip portion 3, the rubber blade 28 is again moved to the photosensitive drum 1.
Contact. As a result, the photosensitive drum 1 is supplied with the developing solution from the developing device 9 and wets. However, when the transfer paper 20 is not conveyed to the transfer nip portion 3, the rubber blade 2
8 squeezes the developer on the photosensitive drum 1
The developer does not accumulate in the transfer nip 3.

Thus, the rubber blade 28
Since the visible image on the photosensitive drum 1 can be squeezed to prevent the developer from accumulating in the transfer nip portion 3, a good image can be easily obtained by mechanical control, and the transfer belt 2 It is possible to reduce the color mixture that occurs through.

Another embodiment will be described with reference to FIG.
Same parts as in the foregoing example uses the same reference numerals, and a description thereof will be omitted. FIG. 5 is a partial longitudinal side view of the image forming apparatus. A transfer medium detecting unit is provided on the transfer belt 2 based on a distance L1 at which the visible image moves from the rubber blade 28, which is a component of the developing solution adjusting unit, to the transfer nip unit 3 on the photosensitive drum 1. Transfer paper detection sensor 1
2 so that the distance L2 that the transfer paper 20 moves from the transfer nip portion 3 to the transfer nip 3 is longer.
And the transfer paper detection sensor 12 are provided respectively.

In such a configuration, when the transfer paper detection sensor 12 detects the transfer paper 20 being conveyed on the transfer belt 2, when the transfer paper 20 is not supplied to the transfer nip portion 3 according to the information. The rubber blade 28 in contact with the photosensitive drum 1 is
Separated from

As described above, the transfer paper detection sensor 12 detects that the transfer paper 20 is being conveyed to the transfer nip portion 3, and the rubber blade 28 is separated from the photosensitive drum 1. At this time, the transfer paper 20 moves from the transfer paper detection sensor 12 to the transfer nip 3 on the transfer belt 2 from the distance L1 at which the visible image moves from the rubber blade 28 to the transfer nip 3.
Is longer, the visible image on the photosensitive drum 1 is conveyed to the transfer nip 3 only when the transfer paper 20 is conveyed to the transfer nip 3, and otherwise, The visible image on the photosensitive drum 1 can be squeezed to prevent the visible image on the photosensitive drum 1 from being conveyed to the transfer nip portion 3. As a result, a good image can be reliably obtained, the color mixture generated via the transfer belt 2 can be reduced, and the control can be simplified because a jam counter need not be provided in the sequence.

Although the present embodiment has been described using an example in which the rubber blade 28 is used, the present invention can be similarly applied to the case of a developing solution adjusting means having the bias roller 11 as a component as shown in FIG.

[0047]

According to the first aspect of the present invention, since the developer is selectively supplied to the transfer nip by the developer adjusting means, the developer is supplied even though there is no transfer paper in the transfer nip. And it is possible to prevent the developer from accumulating in the transfer nip portion, whereby it is possible to obtain a good image without separating the image carrier and the carrier when a jam occurs. At the same time, in the color image forming apparatus, it is possible to reduce the color mixture generated via the conveyance body . In addition, the bias power control means is connected to the electrode member.
Control the applied bias power according to the sequence.
The electrode member selects the developer in the transfer nip.
If there is no transfer paper in the transfer nip,
No longer supplies developer
The developer can be prevented from accumulating in the transfer nip,
This allows the image carrier and carrier to be separated when a jam occurs
Good image easily by electrical control without having to
And a color image forming apparatus
Can reduce the color mixing that occurs through the carrier.
Become. Further, the transfer medium detecting means may be configured so that the transfer medium
Before reaching the transfer nip,
Selectively supplies developer to the transfer nip.
Therefore, even though there is no transfer paper in the transfer nip,
The developer is no longer supplied and the developer is transferred
Can be prevented from accumulating in the
Ensures that the image carrier and carrier are not separated
It is possible to obtain good images,
In image forming apparatus, reduce the color mixture generated through the conveyance body
It becomes possible .

[0048]

[0049]

[0050]

[0051]

According to a second aspect of the present invention, the transfer medium detecting means provided for each image carrier detects the transfer medium on the transport body before reaching each transfer nip portion, and adjusts the developer according to the information. Since the means selectively supplies the developer to each transfer nip, the developer is not supplied even though there is no transfer paper in the transfer nip, and the developer accumulates in the transfer nip. Can be prevented,
Without separating the image carrier and the carrier when a jam occurs, it is possible to reliably obtain a good image, and in a color image forming apparatus, it is possible to reduce color mixture generated via the carrier, Furthermore, since it is not necessary to provide a jam counter in the sequence, the control becomes simpler, and the monitoring of the jam becomes more severe,
It is possible to further reduce the color mixture generated via the carrier . Also, the bias power control means applies the voltage to the electrode members.
To control the bias power supply according to the sequence
Therefore, the electrode member selectively supplies the developer to the transfer nip.
The transfer paper is not present in the transfer nip
Nevertheless, the developer is no longer supplied,
It is possible to prevent the image liquid from accumulating in the transfer nip,
Separation between the image carrier and the carrier when a paper jam occurs.
And easily obtain good images by electrical control
Is possible, and the color image forming
It is possible to reduce the color mixture generated via the sender.
Further, the transfer medium detecting means transfers the transfer medium on the carrier.
Detected before reaching the nip,
Transfer to selectively supply the developer to the transfer nip.
Even though there is no transfer paper in the nip,
The developer is no longer supplied and the developer is transferred to the transfer nip.
Can be prevented from accumulating, so that when a jam occurs
Ensures good image quality without separating the image carrier and carrier
Images can be obtained and color images can be formed.
The device can reduce color mixing that occurs through the carrier.
It works .

[Brief description of the drawings]

FIG. 1 is a partially longitudinal side view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of the image forming apparatus showing the overall configuration.

FIG. 3 is a time chart of the image forming apparatus showing an operation example thereof.

FIG. 4 is a partial longitudinal side view of an image forming apparatus showing another embodiment.

FIG. 5 is a partial longitudinal side view of an image forming apparatus showing another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Conveyor 3 Transfer nip part 11 Electrode member 12 Transfer medium detecting means 20 Transfer medium 28 Developer removing means

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-206379 (JP, A) JP-A-56-95275 (JP, A) JP-A-58-82277 (JP, A) JP-A-56-82277 81870 (JP, A) JP-A-58-187963 (JP, A) JP-A-59-155870 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/10

Claims (2)

(57) [Claims] An image carrier for holding and transporting a developer for forming an image is opposed to a carrier for holding and transporting a transfer medium, and an image on the image carrier is transferred on the transporter. in the image forming apparatus to form a transfer nip for transferring the medium, and selectively supplying the developer regulating means the developer to the transfer nip portion, the transfer medium on the carrier is
Detecting the transfer medium before reaching the transfer nip
A transfer medium detecting means is provided, the developer regulating means, Ba
An electrode member for applying a bias power;
The transfer medium is controlled according to a sequence and the transfer medium is
When detected by the detecting means, the electrode member
Stop applying the bias power and restart detection
An image forming apparatus formed by a bias power supply control unit that opens . 2. A plurality of image carriers for holding and transporting a developer for forming an image are provided opposite to a carrier for holding and transporting the transfer medium, and the images on the plurality of image carriers are transported. In an image forming apparatus having a plurality of transfer nips for transferring to the same transfer medium on a body, a developer adjusting means for selectively supplying the developer to the transfer nip; a transfer medium detecting means for detecting the transfer medium before the medium reaches the transfer nip portion, the transportable
Before the transfer medium on the carrier reaches the transfer nip
A transfer medium detecting unit for detecting the transfer medium is provided for each image carrier, and a bias power supply is applied to the developer adjusting unit.
And the bias power supply according to the sequence.
And the transfer medium is detected by the transfer medium detecting means.
When notified, application of the bias power by the electrode member
To stop and restart as soon as detection is stopped.
An image forming apparatus formed by a source control unit .