JP3006101B2 - Transfer device for 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 electrophotographic photosensitive member, an electrostatic recording dielectric, a magnetic recording magnetic material, and other suitable image forming process means such as electrophotography, electrostatic recording, and magnetic recording. The present invention relates to an apparatus for transferring a transferable image formed on a first image carrier such as a paper to a second image carrier such as paper or a plastic sheet.

More specifically, a second image carrier is superimposed on a first image carrier on which a transferable image has been formed, and a charge is applied to the back surface of the second image carrier by a transfer means to enable transfer. The present invention relates to a transfer device of an image forming apparatus that transfers an image to a second image carrier.

[0003]

2. Description of the Related Art FIG. 5 is a schematic view showing an example of a transfer device in a conventional image forming apparatus. An electrophotographic photosensitive drum 1 as a first image carrier has a predetermined peripheral speed (process speed) in the direction of an arrow. , And is uniformly charged by the primary charging roller 2, and receives an image exposure 3 to form an electrostatic latent image. Next, the developing device 4 applies the toner 5 as charged particles in accordance with the electrostatic latent image to form a transferable visible image 6.

On the other hand, a transfer material 7, which is a second image carrier, is transferred from a paper feed unit (not shown) to a transfer roller 8 as a transfer unit in synchronization with the movement of the developed image 6 on the photosensitive drum 1 by the rotation of the drum. The toner is fed into the nip portion of the photosensitive drum 1, and the reverse voltage of the toner 5 is applied to the back surface of the transfer material 7 by the action of a bias voltage applied to the transfer roller 8 via the metal core 9 by the power supply 10. The visible image 6 of the photosensitive drum 1 is transferred to the transfer material 7 by the electric charge.

After the transfer, the excess charge on the back surface of the transfer material 7 is removed by a static elimination needle 13, and the transferred material 7 is sent to a fixing device (not shown) with the transferred visual image thereon. It is permanently fixed. After passing through the transfer section, the surface of the photosensitive drum 1 is wiped off by a cleaning device 14 to remove the toner remaining after transfer, and is cleaned to be used again for image formation.

The applicant of the present invention has proposed an automatic transfer voltage control system (hereinafter referred to as AT) which can always obtain good transfer performance even when environmental conditions change with respect to the bias voltage of the transfer roller 8.
VC method) was previously proposed as Japanese Patent Application No. 63-27610. In the ATVC method, prior to the image forming process, the photosensitive drum 1 is pre-rotated, a bias voltage is applied to the transfer roller 8 during the pre-rotation, and an output current value at this time is measured by an ammeter 11, and the measured value is measured. To controller 1
Give feedback to 2. The controller 12 adjusts the bias voltage of the power supply 10 so that the output current value becomes a predetermined value, and transfers a constant voltage of the adjusted voltage as it is or a value obtained by correcting the same with a coefficient or the like. Sometimes, the transfer bias is applied to the transfer roller 8, so that even if the impedance of the transfer roller 8 greatly changes due to the environment, a transfer bias having an appropriate constant voltage characteristic can always be obtained.

[0007]

However, in the above-described conventional apparatus, the transfer roller 8 is controlled so that the current value when the photosensitive drum 1 is in direct contact with the transfer roller 8 becomes a predetermined value.
1) When the impedance of the transfer material 7 is high (for example, when using a thick letter or when trying to print on the back surface of the once-printed transfer material 7) 2) The transfer roller 8 However, there is a problem that transfer failure occurs when the impedance is low.

This disadvantage will be described with reference to a voltage-current characteristic diagram of a power supply for applying a bias voltage to the transfer roller 8 shown in FIG. In FIG. 6, a curve A is a curve showing the relationship between the bias voltage V and the output current I of the transfer roller 8 when the photosensitive drum 1 and the transfer roller 8 are brought into direct contact and rotated. the voltage V ₀ so as to obtain a current I ₀ is determined, in the transfer step in the image forming process, the voltage V ₀ is used as a constant voltage bias of the transfer roller 8.

Paper is used as the transfer material 7, and the paper a is sandwiched between the photosensitive drum 1 and the transfer roller 8.
Since the curve is a curve P _1, a constant voltage bias V ₀
When is added, the transfer current is I _1. The problem is whether or not a sufficient amount of the transfer current I ₁ is ensured. However, as shown in FIG. 6, since the transfer current I ₁ is larger than the critical transfer current value I _L , in this case, Transfer is performed.

However, when a transfer material having a large impedance, for example, a thick letter b is used, V-
Since the I characteristic becomes a curve P ₂ and approaches the V axis, the transfer current flows only at I ₂ at the bias voltage V ₀ , and I ₂ <I
It becomes _L and a transfer failure occurs.

In FIG. 6, a curve A 'shows VI and characteristics when the impedance of the transfer roller 8 is smaller than the curve A. At this time, the voltage corresponding to the predetermined current value I ₀ during the previous rotation is V ₀ ′, and the constant voltage bias value applied at the time of transfer is V ₀ ′. Then, even the transfer current in the paper a is now below the critical transfer current value I _L, thereby causing defective transfer. Actually, the curves P ₁ and P ₂ appear as curves slightly away from the V-axis as corresponding to the curve A ′, but are omitted for simplicity of description because there is little difference from the solid line.

[0012] In order to ensure the transfer performance, adequate supply of charge to the transfer material 7, i.e. it is that required to ensure the current value I _1, I ₂ above the critical transfer current value I _L, In the conventional ATVC system, since it is assumed that the current value I ₀ during the pre-rotation and the current value I ₁ (or I ₂ ) during the transfer are in a certain proportional relationship, the impedance of the transfer material 7 changes. Or the impedance of the transfer roller 8 changes,
As described above, the occurrence of transfer failure was inevitable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a transfer apparatus which does not cause a transfer failure.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a transfer apparatus for electrostatically transferring a visible image on an image carrier to a transfer material by a transfer means. And a transfer device of the image forming apparatus, which detects an output current of the power supply at this time, and performs a transfer operation after the leading end with a transfer voltage determined using the detected current. I do.

<Operation> That is, a constant voltage is applied to the transfer means by the power supply at the leading end of the transfer material, the output current of the power supply at this time is detected, and the transfer current determined by using the detected current is used. By performing the transfer operation after the copy section, an appropriate transfer operation can be performed even if the resistance value of the transfer unit or the transfer material changes.

[0016]

<Embodiment 1> FIG. 1 is a sectional view of a main part of a first embodiment of the apparatus, in which the same parts as those of the conventional apparatus of FIG. The transfer material 7 is conveyed in the direction of the arrow. While the transfer material 7 is moved by a distance l ₀ from the leading end in the traveling direction while being sandwiched between the photosensitive drum 1 and the transfer roller 8, the ammeter 11 supplies the transfer material 7 from the power source 10. Is measured.

The result of the measurement is sent to the controller 12 to obtain a current value I ₂ averaged over the distance l ₀ . The controller 12 the current value I ₂ is smaller than the critical current value I _L causing defective transfer raises the output voltage of the power source 10 so as to obtain a sufficient current value I _l in transcription.

FIG. 2 shows how the output voltage V and the output current I change according to the distance L from the leading end of the transfer material 7 under the control of the controller 12. Here, as the initial applied voltage V ₀ , a predetermined constant value may be used, or a voltage value obtained by the above-mentioned ATVC method may be used.

In the above case, a transfer failure occurs over a distance l ₀ from the leading end of the transfer material 7,
By taking the distance l ₀ sufficiently small, it may be performed to control the above using region that is not to be printed therein to a large extent of print. In addition, in the case of EDP output or the like, there is an example in which a header print having a very small print amount is discharged before the text. In such a case, the above-described control may be performed using a margin portion of the header print. In the continuous printing, it goes without saying that the appropriate voltage value obtained at the time of printing the first sheet may be applied to the second and subsequent sheets.

Experimental Example A photosensitive drum 1 having an organic semiconductor formed on an aluminum cylinder having an outer diameter of 30 mm was used.
The roller was rotated at a speed of mm / sec, and charged uniformly by the charging roller 2 to a dark area potential of −600 V. Then, a bright portion potential of -150 V is obtained by image exposure 3, and a latent image is formed by using the image exposure 3 as an appropriate pattern. Then, reverse development is performed by a developing device 4 to apply toner 5 to the bright portion, thereby developing a visible image. 6
I got The toner 5 had a volume average particle size of 6.5 μm and an average charge amount of 10 μc / gr. As a transfer roller 8, an EPDM is placed on a stainless steel core 9 having an outer diameter of 8 mm.
An elastic layer having a specific resistance of about 10 ⁸ Ω · cm and an Asker C hardness of 30 ° with a metal oxide dispersed therein was formed, and the outer diameter was 20 mm.
Was used. The transfer roller 8 is moved to a total pressure of 1000
Gr was pressed against the photosensitive drum 1 to form a nip of about 2 mm, and the image was transferred to the back surface of a high-impedance transfer material (paper b) once printed on one side.

First, as a reference example, V ₀ = 1.7 KV was obtained according to I ₀ = 10 μA according to the conventional ATVC method, and was transferred to paper b. With this, the transfer current was I ₂ =
2.5 μA, which was less than the critical transfer current value I _L = 3 μA, resulting in poor transfer, scattering around characters and disturbance of halftone images.

According to the present embodiment, l
After detecting I ₂ = 2.5 μA at ₀ = 30 mm, the output voltage of the power supply 10 was controlled from V ₀ = 1.7 KV to V ₁ = 2.5 KV so that the current I ₁ would be I ₁ = 4 μA. . When the transfer was performed in this manner, no transfer failure as in the reference example described above occurred. <Embodiment 2> FIG. 3 is a plan view of a main part of a device according to a second embodiment. The same parts as those in FIG. In FIG. 3, reference numerals 7 and 7a denote transfer materials. The transfer material 7 has a width covering the entire length of the transfer roller 8, whereas the transfer material 7a is narrower than the transfer material 7. In the transfer step, the transfer roller 8 and the photosensitive drum 1
There occurs moiety W _1, W ₂ in direct contact.

In the contact portions W ₁ and W ₂ , the current flows more easily than the portion via the transfer material 7 a, and the current flowing directly to the photosensitive drum 1 is subtracted from the value measured by the ammeter 11 to obtain the transfer material. It is necessary to calculate the value of the current flowing through 7a and control it by comparing it with a reference value.

Referring to FIG. 3, the current value I ₀ is obtained when the entire width W ₀ of the transfer roller 8 is in contact with the photosensitive drum 1 at the applied voltage V ₀ , so that the current flowing through the widths W ₁ and W ₂ is obtained. The value is I ₀ × ((W ₁ + W ₂ ) / W ₀ ).

[0025] Therefore, if the current value obtained when through the transfer material 7a and Ia, since _{Ia-I 0 × ((W} 1 + W 2) / W 0) is a current flowing through the transfer material 7a If this current value is smaller than I _L × ((W ₀ −W ₁ −W ₂ ) / W ₀ ), the voltage of the power supply 10 is increased and [Ia′−I ₀ ′ × (W ₁ + W ₂ )]. / W _{0)]> I L × ((W 0} -W 1 -W 2) / W 0) that _{is, Ia '> I L × (} (W 0 -W 1 -W 2) / W 0) + I 0' × ((W ₁ + W ₂ ) / W ₀ ). Here, I ₀ ′ represents the transfer roller 8 and the photosensitive drum 1 at the boosted output voltage value V ₁ .
Is the value of the current flowing when it is in direct contact with the entire width. <Reference Example> FIG. 4 shows a main part of a reference example apparatus. The same parts as those in FIG. 15 is a cassette, 16 is an intermediate tray, 17 is a paper feed roller, 18
Denotes a re-feed roller, 19 denotes a register roller, and 20 denotes a fixing device.

Reference numerals 21, 22, and 23 denote three transfer paths for the transfer material 7, and the transfer material 7 is transferred as follows. First, when printing is performed on one surface of the transfer material 7, the transfer materials 7 taken out one by one from the cassette 15 by the paper feed roller 17 are conveyed along a conveyance path 21 indicated by a broken line. That is, the toner is guided to the nip between the transfer roller 8 and the photosensitive drum 1 in synchronization with the photosensitive drum 1 by the register roller 19, and is stored in the intermediate tray 16 via the fixing device 20.
Prepare for the image formation of the surface. When printing on only one side is performed, the transfer material 7 is discharged to the transport path 23 after passing through the fixing device 20.

During image formation on the second side, the transfer material 7 taken out of the intermediate tray 16 by the re-feed roller 18 is
After reaching the register roller 19 through the transport path 22, the sheet is discharged to the outside through the transport path 21 after passing through the transport path 21 to the fixing device 20 and out of the fixing device 20.

In the present embodiment, in the pre-rotation step before the image forming step, the transfer material 7 is once taken out of the cassette 15 by the transport path 21 and guided to the nip between the transfer roller 8 and the photosensitive drum 1. At this time, an appropriate transfer bias is determined by the controller 12 based on the measured value obtained by the ammeter 11. At this time, since the visible image 6 does not exist on the photosensitive drum 1, the transfer material 7 remains blank and passes through the fixing device 20.
It is stored in the intermediate tray.

The above is the pre-rotation step. In the image forming step for the first side, the transfer material 7 is taken out of the intermediate tray 16 by the re-feed roller 18, passed through the transport path 22 and the register roller 19, and transferred to the transfer roller 8. And the nip of the photosensitive drum 1. At this time, the bias value of the power supply 10 is maintained at the value determined during the above-described pre-rotation, and the visible image 6 is transferred to the first surface of the transfer material 7. After passing through the fixing device 20, in the case of single-sided printing, the sheet is carried out to the outside via the transport path 23, and in the case of double-sided printing, the sheet is again stored in the intermediate tray 16 via the transport path 21 and prepared for image formation on the second side.
The transfer bias value during image formation on the second side is maintained at the same value as the first side.

In the case of the present embodiment, the output voltage of the power supply 10 is always maintained at a constant value at the time of transfer in the image forming process, so that stable transfer performance can be obtained.

In the embodiments, the transfer roller has been described as the transfer means. However, the gist of the present invention is not limited to the transfer roller, but may be any of a corona transfer method, a belt transfer method, a transfer drum method, and the like. Needless to say, it can also be applied to.

[0032]

As described above, according to the present invention, in a transfer apparatus for electrostatically transferring a visual image on an image carrier to a transfer material by a transfer means, a power supply is applied to the transfer means at the leading end of the transfer material. A voltage is applied, the output current of the power supply at this time is detected, and the transfer operation after the leading end is performed at a transfer voltage determined by using the detected current. , The proper transfer operation can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of an apparatus according to a first embodiment.

FIG. 2 is a diagram showing a transition of a transfer bias voltage and a current value from a leading end to a trailing end of a transfer material.

FIG. 3 is a plan view of a main part of the device according to the second embodiment.

FIG. 4 is a schematic view of a main part of the device of the reference example.

FIG. 5 is a schematic diagram illustrating an example of a conventional image forming apparatus.

FIG. 6 is a voltage-current characteristic curve diagram of a bias power supply for a transfer roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (1st image carrier) 5 Toner (charged particle) 6 Visible image 7 Transfer material (2nd image carrier) 8 Transfer roller (transfer means) 10 Power supply 11 Current detector 12 Controller

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroto Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Akihiko Takeuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideyuki Yano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideo Nanataki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-228179 (JP, A) JP-A-3-223779 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (1)

(57) [Claims] And a transfer means for transferring a visible image on the image carrier by a transfer means.
In a transfer device that electrostatically transfers to a transfer material, a constant voltage is applied to the transfer means by a power supply at the leading end of the transfer material
The output current of the power supply at this time is detected, and this detected current is
The transfer operation after the leading end is performed with the transfer voltage determined using
A transfer device of an image forming apparatus characterized by Nau.