JPH05281860A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce waste toner, to eliminate a cleaner, and to miniaturize a device, in an image forming device for an electrophotographic copying machine, an optical printer, etc. CONSTITUTION:The image forming device has a constitution so that a toner sticking region 1A for sticking toner is provided on the end part of an image carrier 1, and simultaneously, a surface potential measuring means 101 detecting the surface potential of a toner layer on the toner sticking region 1A, a control means 102 instructing a change in a transfer current applied to a transfer means 51, corresponding to the change in the detected surface potential, and a current changing means 103 changing the transfer current applied to the transfer means 51 by the instruction, are provided, as well.

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 such as an electrophotographic copying machine and an optical printer. Copiers and optical printers using electrophotography are widely used because of their high speed, high resolution, and low noise. In electrophotography, generally, a uniformly charged surface of a photoconductor is exposed with a laser or the like according to image information to form an electrostatic latent image. After that, a charged toner is attached to the electrostatic latent image on the photoconductor by a developing process to form a visible image. After the visible image of the toner is electrostatically transferred (transferred) onto the recording paper, it is fixed by heat, pressure, light or the like to obtain a copy or print.

Conventionally, in the developing process, a two-component developing method has been adopted in which a carrier which is a magnetic powder and a resinous toner are mixed and the toner is charged by frictional charging. However, in the two-component development, (1) it is necessary to control the mixing ratio of the carrier and the toner, (2) the device becomes large because a carrier is required in the developing device, and (3) triboelectric charging is used to charge the toner. However, there is a problem that the toner charge amount changes due to environmental changes.

In order to solve the above-mentioned problems, only a toner is required in the developing device, and a one-component developing device which simplifies the structure of the device has been actively developed and put into practical use. In recent years, in particular, optical printers are often used in offices and for personal use, and as a result, devices having a small installation area have been desired. As a point of downsizing of the apparatus, it is necessary to make the whole process small, and for that purpose, one-component development which can make the developing apparatus small is suitable. However, even in this one-component developing method, due to the constraint that each process must be arranged around the photoconductor,
There is a limit. Therefore, a method of omitting a part of the process can be considered as an important factor for downsizing. In each process, it is possible to reduce a large space by reducing the size of the waste toner container existing in the cleaner section and by eliminating the cleaner section itself. For that purpose, it is necessary to improve the transfer efficiency and the toner utilization efficiency.

[0004]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 8 shows the configuration of the optical printer. The basic configuration of the device is that a uniform charging device such as a corona charger, a conductive brush charger, a conductive roller charger is provided around the photosensitive drum 1 such as an organic photosensitive member, a Se photosensitive member, and an a-Si photosensitive member. 2,
Image exposure device 3 such as laser optical system, LED optical system, EL optical system, liquid crystal optical system, developing device 4 such as two-component magnetic brush developing device, magnetic one-component developing device, non-magnetic one-component developing device, corona discharge device A transfer device 5 such as a conductive roller transfer device, a cleaner 6 such as a brush cleaner and a blade cleaner, and a charge eliminating lamp 7 are arranged, and a fixing device 9 is arranged on a conveying path for conveying the recording paper 8.

First, the surface of the photosensitive drum 1 is charged by the uniform charger 2. Next, the surface of the photosensitive drum 1 is image-exposed by the image exposure device 3 according to a predetermined pattern corresponding to the image. In the exposed portion on the photosensitive drum 1, the charge is reduced and an electrostatic latent image is formed.
When the photoconductor drum 1 passes the developing device 4 (here, a one-component developing device is shown), the pre-charged toner adheres to the electrostatic latent image on the photoconductor drum 1 to form a toner image. It On the other hand, the recording paper 8 on which the image is printed is supplied to the position where it comes into contact with the toner image formed on the photosensitive drum 1. The transfer unit 5 includes the recording paper 8 and the photosensitive drum 1
Is installed below the recording sheet 8 and charges the recording sheet 8 with a polarity opposite to the toner charge, and electrostatically transfers the toner image on the photosensitive drum 1 onto the recording sheet 8. The recording paper 8 carrying the toner image is fixed on the recording paper 8 by heat and pressure while passing through the fixing device 9, and the printing is completed. On the other hand, the toner remaining on the photosensitive drum 1 after the toner image is transferred onto the recording paper 8 is cleaned by the cleaner 6 and stored in the waste toner container 10 as the waste toner 10a. Further, the charge removal lamp 7 removes residual charges from the photoconductor drum 1, restores it to the initial state, and repeats the printing operation.

Next, the roller transfer will be described with reference to FIG. The transfer roller 51 includes a conductive elastic layer 51b and metal shafts 51a exposed at both ends, and the metal shaft 51a is supported by bearings 53. A spring 54 for the bearing 53
Is attached, and a load is applied to press the transfer roller 51 against the photosensitive drum 1. The bearing 53 used here has conductivity, and a bias is applied to the transfer roller 51 from the power source 52 via the bearing 53 and the spring 54.

[0007]

In the conventional image forming apparatus, since the transfer current applied from the power source 52 is constant during roller transfer, the toner adhesion amount on the photosensitive member due to humidity fluctuation, The optimum transfer efficiency greatly changes depending on the toner charge amount. In particular, at high humidity, the amount of adsorption on the surface of the photoconductor becomes strong, and the amount of toner on the drum increases even if the toner has the same charge amount. As an example of this, experimental results are shown in FIG. FIG. 10 shows the relationship between the transfer current and the transfer efficiency when the toner adhesion amount changes due to humidity fluctuation. As shown in FIG. 10, when the toner adhesion amount is increased, the transfer current that maximizes the transfer efficiency is increased. The same changes when the toner charge amount increases. When the toner adhesion amount or the toner charge amount changes, it is necessary to increase or decrease the transfer current in order to increase the transfer efficiency, so that the optimum transfer current is obtained. In the conventional transfer, since the transfer current is set to an intermediate value in which the toner charge amount fluctuates, the transfer efficiency is lowered due to the fluctuation of the toner charge amount, and as a result, the toner remains on the photoconductor after the transfer, and the waste toner 10a Became a factor to increase.

As described above, in the roller transfer in which the transfer current is constant, the transfer efficiency decreases when the toner charge amount or the adhesion amount fluctuates, and as a result, the waste toner 10a increases. The transfer efficiency in the conventional process including the cleaner 6 and the waste toner container 10 which do not consider the miniaturization of the process is about 75 to 85%, and the amount of the waste toner 10a is about 20% of the supplied toner amount. Therefore, the amount of supplied toner is about 2
Waste toner container 10 and cleaner 6 corresponding to 0% were required. In order to reduce the size of the waste toner container 10 or to eliminate the waste toner 10a and eliminate the cleaner 6, it is necessary to increase the transfer efficiency to 97% or more regardless of the variation in the toner charge amount and the toner adhesion amount.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to reduce the amount of waste toner, eliminate the need for a cleaner, and reduce the size of the apparatus by increasing the transfer efficiency. It is an object of the present invention to provide an image forming apparatus that can be used.

[0010]

FIG. 1A is an explanatory view of the principle of the present invention. In FIG. 1A, reference numeral 51 is a transfer means for transferring the toner image formed on the surface of the image carrier 1 to the recording paper 8, and 1A is a toner adhering device for attaching the toner provided at the end of the image carrier 1. Area 101 is a surface potential measuring means for detecting the surface potential of the toner layer on the toner adhering area 1A, and 102 is a control for instructing a change in the transfer current applied to the transfer means 51 according to the change in the detected surface potential. Means, 103 is a current changing means for changing the transfer current according to an instruction.

FIG. 1B is an explanatory view of the principle of another invention. In FIG. 1B, 15 is a developer carrying member 11.
The developer 13 that is pressed and arranged on top of the developer 13
Is a layer thickness regulating member that regulates the toner to a constant thickness by charging, 51 is a transfer unit that forms a toner image on the surface of the image carrier 1 and then transfers the toner image to the recording paper 8, and 101 is the layer thickness regulating member 15. Surface potential measuring means for detecting the surface potential of the toner layer on the charged developer carrier 11, 102 is a control for presenting a change in the transfer current applied to the transfer means 51 according to the detected change in the surface potential. Means, 103 is a current changing means for changing the transfer current applied to the transfer means 51 according to an instruction.

[0012]

The surface potential of the toner layer in the toner adhering area formed on the end of the image carrier or the toner layer on the developer carrier charged by the layer thickness regulating member is detected, and transfer is performed according to the detected surface potential. Instruct the change of transfer current applied to the means,
The transfer current is changed according to the instruction.

As described above, since the transfer current applied to the transfer means is controlled to an optimum value, a high transfer efficiency can always be obtained in the transfer section. As a result, the amount of waste toner can be reduced, the cleaner can be eliminated, and the overall size of the apparatus can be reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 5 are views showing an embodiment of the present invention.
In FIG. 2, reference numeral 1 is a photosensitive drum (image bearing member) in which a function-separated organic photosensitive member is applied onto an aluminum drum. The photosensitive drum 1 is rotated at a peripheral speed of 70 in the direction of arrow A.
Rotate at mm / s. The surface potential of the surface of the photosensitive drum 1 is approximately − by a scorotron (not shown) in advance.
After being uniformly charged to 650 V, an electrostatic latent image is formed by a laser optical unit (not shown).

Reference numeral 11 denotes a developing roller as a developer bearing member, which conveys and supplies the developer (toner) 13 to the electrostatic latent image on the photosensitive drum 1 by rotating it around a rotating shaft 12 made of metal. To do. In this apparatus, the toner 13 is a non-magnetic insulating material and is a resin one-component toner. This toner 13
Has a volume resistivity of 4 × 10 ¹⁴ Ω · cm and an average particle diameter of 12 μ.
m is a polyester type toner containing 0.5% of silica external additive.

The developing roller 11 has an average pore diameter of about 10 μm.
m, number of cells about 200 cells / inch, volume resistivity 10 ⁴ ~
A porous urethane sponge (Rubicell made by Toyo Polymer) having a resistance of 10 ⁷ Ωcm and a hardness of about 23 degrees (Asker C hardness meter) was used. The peripheral speed is set to the peripheral speed of the photosensitive drum 1, which is 2.
Rotate 5 times 175 mm / s. A power source 14 is used to apply a developing bias to the developing roller 11. At this voltage, the surface potential of the photosensitive drum 1 is -650.
However, it is normally set to about -220V.

Numeral 15 is a charging blade as a layer thickness regulating member, which charges the toner 13 to a predetermined charge amount and regulates the layer thickness of the toner 13 on the developing roller 11 to a constant thickness. The charging blade 15 is fixed to the support block 17. The support block 17 is attached rotatably around a rotation fulcrum 18, and is subjected to a constant pressure by a spring 19. Therefore, the charging blade 15 is pressed in the direction normal to the center of the developing roller 11.

The charging blade 15 is made of stainless steel (SUS304-CSP-3 / 4H) and has a round-edged tip with a thickness of 0.1 mm.
0.05 mm), the bending length from the support block 17 is 3 mm, and the pressing pressure against the developing roller 11 is 35 mm.
It was set to be gf / cm. Between the charging blade 15 and the developing roller 11, in order to reduce the environmental dependence of the amount of charged electric charge of the toner 13 and to stabilize it for a long time,
The power supply 20 applies a voltage of -100V.

When the toner 13 passes between the developing roller 11 and the charging blade 15, the toner 13 is triboelectrically charged by the toner 13 and the layer charging blade 15 to give an electric charge to the toner 13. Further, a voltage is applied between the developing roller 11 and the charging blade 15 to inject charges from the charging blade 15 into the toner 13. Therefore, the toner 13 is provided with a charge by frictional charging and charge injection, and a stable charge amount with little change in the charge amount due to changes due to the environment and changes over time can be obtained.

Reference numeral 21 denotes a reset roller as a reset member. The reset roller 21 collects the toner 22 remaining on the developing roller 11 after developing the electrostatic latent image on the photosensitive drum 1, and Toner 1 on the developing roller 11
3 has an auxiliary function of making the layer thickness of the toner 16 on the developing roller 11 uniform. For the reset roller 21, an ester urethane sponge (Everlight SK-E made by Bridgestone) having a cell number of about 40 cells / inch and a volume resistivity of 10 ⁴ Ω · cm was used, and the peripheral speed was set to 228 mm / s. ..

Between the reset roller 21 and the developing roller 11, the toner 1 negatively charged on the developing roller 11 is provided.
A voltage is applied by the power supply 24 so that the electric power can be supplied electrically. This operation is set to about -100V. The voltage generated by the power source 20 and the voltage generated by the power source 24 are
Since they are almost the same, you may share both. 25
And 26 are paddle rollers for moving the toner 13 to the vicinity of the developing roller 11, which are made of resin.

Next, the transfer section will be described with reference to FIG.
In FIG. 3, reference numeral 51 is a transfer roller as a transfer means, and the transfer roller 51 includes a metal shaft 51 a and a conductive elastic layer 5.
1b. A bias is applied to the transfer roller 51 from the power supply 52, and the toner image formed on the surface of the photoconductor drum 1 is transferred from the back surface of the recording paper 8 to the recording paper 8 by contacting the control unit 5.

As shown in FIG. 4, a toner adhering area 1A is provided at the end of the photosensitive drum 1 that does not affect printing, a latent image is formed by an image exposure device, and development is performed by the developing roller 11. Reference numeral 101 is a surface potential meter as a surface potential measuring means, and the surface potential meter 101 measures the surface potential of the toner layer in the toner adhesion area 1A.

Reference numeral 102 denotes a controller as a control means. The controller 102 takes in the surface potential of the toner layer measured by the surface electrometer 101, and based on the amount of change, increases or decreases the transfer current stored in advance. The current changing means) 103 is instructed. Transfer current changing device 10
3 changes the transfer current supplied from the power supply 52 in accordance with an instruction from the controller 102.

Next, the operation will be described. Toner adhesion area 1A developed by the developing roller 11 at the end of the photosensitive drum 1.
The surface potential of the toner layer is constantly measured by the surface electrometer 101 at the time of transfer, and the obtained surface potential is taken in by the controller 102, and the change value of the transfer current stored in advance from the change amount thereof is transferred to the transfer current changing layer. Send a signal to 103,
The transfer current changing device 103 changes the transfer current supplied from the power supply 52.

FIG. 5 shows an example of the amount of change in the surface potential and the increase / decrease in the transfer current stored in the controller 102. In this example, when the surface potential fluctuates (toner charge amount) of ± 10%, it is possible to always achieve the transfer efficiency of 90% or more by changing the transfer current by ± 2 μA.

As a result, the amount of waste toner decreases, and
Since the cleaner is unnecessary, the device can be downsized. Next, FIG. 6 is an operation explanatory view of the second embodiment of the present invention. The configuration of this embodiment is the same as that of FIGS. 2 to 4 except for the type of toner 13 used. 2 to 4, a styrene-acrylic polymerized toner prepared by a polymerization method (suspension polymerization method) is used as the toner 63.

FIG. 6 shows the relationship between transfer current and transfer efficiency when polymerized toner is used. The transfer efficiency could be increased to 97% by using the polymerized toner. It goes without saying that the same effects as those of the above-mentioned embodiment can be obtained in this embodiment as well. Next, FIG. 7 is a diagram showing a third embodiment of the present invention.

In FIG. 7, 15 is a charging blade as a layer thickness regulating member, which charges the toner 13 and regulates the layer thickness of the toner 13 on the developing roller 11 to a constant thickness. Reference numeral 101 is a surface electrometer 1 which is a back surface electrometer (surface electric potential measuring means) for detecting the surface electric potential on the toner layer formed on the developing roller 11 and charged by the changing blade 15.
The value obtained by 01 indicates that the power supply 14 is the developing roller 11
Is the effective developing bias Vbs obtained by superimposing the developing bias Vb applied to the developing roller 11 and the toner layer potential Vt formed by the toner layer on the developing roller 11.

Reference numeral 102 denotes a controller as a control means. The controller 102 takes in the surface potential of the toner layer measured by the surface electrometer 101, and based on the amount of change, increases or decreases the transfer current stored in advance. The current changing means) 103 is instructed. Transfer current changing device 10
3 changes the transfer current supplied from the power supply 52 in accordance with an instruction from the controller 102.

The toner layer on the developing roller 11 charged by the charging blade 15 is detected by the surface electrometer 101, and the detected effective developing bias Vbs is fetched by the controller 102, and the transfer amount stored in advance is stored from the change amount. The change value of the current is sent to the transfer current changing device 103, and the transfer current supplied from the power source 52 is changed by the transfer current changing device 103.

As shown in FIG. 5, when a surface potential fluctuation (toner charge amount) of ± 10% occurs, the transfer current is ±
It was possible to always achieve a transfer efficiency of 90% or more by changing 2 μA. When a styrene-acrylic toner produced by a polymerization method (suspension polymerization method) was used as the toner 13, the transfer efficiency could be increased to 97% as shown in FIG.

Also in this embodiment, the same effect as that of the above embodiment can be obtained.

[0034]

As described above, according to the present invention,
Since the transfer current is controlled to an optimum value, a high transfer efficiency can always be obtained in the transfer section, and a printer with less waste toner or a cleaner-less printer can be realized. Therefore, the size of the entire device can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is a diagram showing a developing unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a transfer unit.

FIG. 4 is a diagram showing a photosensitive drum.

FIG. 5 is a graph showing the relationship between the rate of change in surface potential and the change in transfer current.

FIG. 6 is a graph showing the relationship between toner type and transfer efficiency according to the second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a diagram showing a conventional example.

FIG. 9 is an explanatory diagram of roller transfer.

FIG. 10 is an explanatory diagram of the optimum transfer efficiency due to the difference in the toner adhesion amount.

[Explanation of symbols]

 1: Photosensitive drum (image bearing member) 1A: Toner adhering area 8: Recording paper 11: Developing roller (developer bearing member) 12: Rotating shaft 13: Toner (developer) 14: Power supply 16: Charging blade (layer thickness) Regulation member) 17: Support block 18: Rotation fulcrum 19: Spring 20: Power supply 21: Reset roller 24: Power supply 25, 26: Paddle roller 51: Transfer roller (transfer means) 51a: Metal shaft 51b: Elastic layer 52: Power supply 101 : Surface potential meter (surface potential measuring means) 102: Controller (control means) 103: Transfer current changing device (current changing means)

Claims (3)

[Claims] 1. An image forming apparatus for forming an image by transferring a toner image formed on a surface of an image carrier (1) onto a recording paper (8) by a transfer means (51), wherein the image carrier (1) ) Is provided with a toner adhering area (1A) for adhering toner, and surface potential measuring means (101) for detecting the surface potential of the toner layer on the toner adhering area (1A), and the detected surface potential The transfer means (51) according to the change
Control means (10) for instructing a change in the transfer current applied to the
2) and a current changing unit (103) for changing the transfer current applied to the transfer unit (51) according to the instruction. 2. A developer (13) is charged and regulated to a constant thickness by a layer thickness regulating member (15) arranged by being pressed against the developer carrier (11) with a predetermined pressure, and the image carrier ( 1)
An image forming apparatus for forming a toner image on the surface of a sheet, and then transferring the toner image onto a recording paper (8) by a transfer means (51) to form an image, the development being charged by the layer thickness regulating member (15). Surface potential measuring means (101) for detecting the surface potential of the toner layer on the agent carrier (11), and the transfer means (5) according to the change in the detected surface potential.
Control means (1) for presenting a change in transfer current applied to (1)
02) and current changing means (103) for changing the transfer current applied to the transfer means (51) according to the instruction. 3. The image forming apparatus according to claim 1, wherein a toner prepared by a polymerization method is used as the developer (13).