JP3050935B2 - 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 apparatus, an electrostatic printer, etc., which forms an electrostatic latent image on an image carrier such as a photoreceptor and develops the electrostatic latent image. The present invention relates to an image forming apparatus provided with a transfer device for transferring an image to a transfer material such as paper.

[0002]

2. Description of the Related Art In electrophotographic apparatuses and electrostatic printers,
After forming an electrostatic latent image on a photoreceptor (image carrier), a developer is electrostatically attached to the electrostatic latent image to form a developer image, and then the developer image is transferred by a transfer unit. Is recorded by transferring it to paper. As the transfer device, electrostatic means such as a corona transfer method and a roller transfer method and mechanical means such as an adhesive transfer direction are known.

Further, since an electrostatic latent image and a developer that cannot be completely transferred remain on the photoreceptor after transfer, the residual developer is removed by a cleaning device, and then the electrostatic latent image is removed. Removed by static eliminator. Thereafter, the same basic operation is repeatedly performed.

[0004] In recent years, along with the demand for downsizing of the apparatus, the harmfulness of ozone generated by corona discharge has been raised as a problem. It has been demanded.

[0005]

However, there are several reasons why the roller transfer method has not been widely used while having the above advantages.

In roller transfer, it is required to press a transfer material such as paper against a developer image surface such as a photoreceptor with an appropriate pressure. If the pressure is insufficient, uneven transfer is caused. High mechanical precision (straightness: about ± 50 microns) because (toner) sticks and causes transfer omissions
And moderate softness corresponding to this (JIS hardness of about 10
40 °), but it was difficult to achieve both of them with the conductive rubber used conventionally.

Particularly, when a sheet having a thickness of 100 microns is used, an excessive pressure is generated to cause transfer failure.
Complex control such as separation is required.

In addition, it is necessary to maintain the electric resistance for applying an electrostatic force to the toner image to a value which can prevent the destruction of the recording material due to electric discharge in various environments. The range is constrained. Against this background, there is a need for an image forming apparatus that solves the above-mentioned problems and sufficiently satisfies the required characteristics.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of easily maintaining an appropriate pressing force on a material to be transferred without an extremely high mechanical precision required with a very simple structure. It is assumed that.

[0010]

In order to solve the above-mentioned problems, the present invention is directed to a latent image forming means for forming an electrostatic latent image on an image carrier, and the latent image forming means. Developing means for supplying a developer to the formed electrostatic latent image to form a developer image on the image carrier, supplying means for supplying a transfer material to the image carrier, and contacting the image carrier Rotatably provided on the conductive base tube and the peripheral surface of the conductive base tube.
Having a conductive fiber provided, transfer means for transferring the developer image formed by the developing means onto the transfer material,
And a voltage applying means for supplying a transfer voltage to said transfer means, said transfer means, 70 g / cm to said image bearing member
It is pressed by the following pressure and the distance between the tips of the fibers
Fiber density from 500 so that separation is 3mm or less
1000 fibers / cm ² , the thickness of the fiber is 1 to 15 denier
The length of the fiber is 3 to 15 mm, and
A voltage is supplied from the voltage applying means to the conductive element tube.
It is those that. And a latent image forming means for forming an electrostatic latent image on the image carrier, and a developer supplied to the electrostatic latent image formed by the latent image forming means to supply the developer onto the image carrier. Developing means for forming a developer image on the image carrier, supplying means for supplying a transfer material to the image carrier, and a conductive element tube rotatably provided in contact with the image carrier, and Lap of
Transfer means for transferring a developer image formed by the developing means onto the transfer material, the conductive means having conductive fibers provided on a surface thereof, and coaxially provided at both ends of a conductive element tube of the transfer means.
The outer diameter is smaller than the outer diameter of the conductive fiber.
Guide roller for pressure adjustment and transfer to the transfer unit
And a voltage application means for supplying a voltage, the transfer unit
Is pressed against the image carrier at a pressure of 70 g / cm or less.
And the distance between the fiber tips is 3 mm or less.
So that the fiber density is between 500 and 1000 fibers / cm
² , the thickness of the fiber is 1 to 15 denier, the length of the fiber
3 to 15 mm, and with respect to the conductive tube
A voltage is supplied from the voltage applying means .

[0011]

By pressing the material to be transferred against the image carrier by means of the brush-like conductive fibers having elasticity, it is possible to obtain a pressing force on the image carrier with a large mechanical allowance that enables appropriate transfer. I made it possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIGS. FIG. 2 shows a recording apparatus, and a photosensitive drum 1 as an image carrier is rotatably provided in a substantially central portion of a main body H in an arrow A direction. The photoconductor drum 1 is formed of an organic photoconductor (OPC) -based photoconductive material.

Around the photosensitive drum 1, the charging charger 2, an image exposure device (electrostatic latent image forming means) 3 comprising an LED (light emitting diode) array, and a developing device ( (Developing means) 4, a transfer device 5, and a cleaning device 6 are provided.

The charging charger 2 is located above the photosensitive drum 1, and the surface of the photosensitive drum 1 is -5.
The negative charge is made substantially uniformly at 00 to -800 volts.

The image exposure device 3 irradiates the surface of the photosensitive drum 1 with LED light to form an electrostatic latent image on a charged area according to image information to be recorded. Further, the developing device 4 supplies the developer T to the developing roller 8 in a hopper 7 in which a one-component developer (toner) T having a triboelectric property and having an average particle diameter of 5 to 15 micrometers is stored. And a developing roller 8 for developing the developer supplied from the intermediate roller 9 by rubbing it against the photosensitive drum 1.

The developing roller 8 has a capacity of 10 ² -10 ⁸ Ωcm
Surface layer 1 made of conductive elastic resin having electric resistance
An elastic layer 11 made of foamable urethane, silicone rubber, EPDM, or the like is disposed inside the elastic layer 11 to form an elastic roller 8 as a whole.

An elastic blade 12 made of phosphor bronze, urethane or silicone resin for forming a thin layer is pressed against the developing roller 8 while frictionally charging the developer T, and the developer passing therethrough is pressed. T is the photosensitive drum 1
One or two developer layers are formed with negative triboelectric charge of the same polarity as the above. The surface layer 10 of the developing roller 8 needs to be selected in consideration of frictional charging of the developer and appropriate elasticity and friction.

Further, a bias power source 13 as a voltage applying means is connected to the developing roller 8, and is electrically connected to the surface layer 10. As a result, a predetermined developing bias (-140 to -400 V) is applied during development.

The transfer device 5 includes a cylindrical brush 15,
Substantially below the photoconductor drum 1, the photoconductor drum 1 is provided facing the peripheral surface of the photoconductor drum 1 via a paper transport path 14. The cylindrical brush 15 is in light contact with the photosensitive drum 1 while rotating at a different peripheral speed of about 1% to about 1%.

The cylindrical brush 15 is configured as shown in FIG. That is, in the figure, reference numeral 15a denotes a cylindrical tube 15a which has been subjected to a conductive treatment with metal, paper, plastic, or the like, and a conductive fiber formed on the outer surface of the cylindrical tube, for example, by mixing conductive carbon with rayon. It is made by flocking 15b at a suitable density or knitting it into a fabric and winding it.

The cylindrical brush 15 includes 800 to 2000
A voltage of volts is applied, and the paper 1 conveyed here
6 and is charged to 400 to 800 volts, and the toner image on the photosensitive drum 1 is electrostatically attracted and transferred from the photosensitive drum 1 to the paper 16. What is important in the cylindrical brush 15 is the characteristics of the conductive fiber 15b. Various cylindrical brushes 1 made of various conductive fibers are described below.
Experimental results on transfer characteristics performed by trial production of No. 5 are shown, and preferable characteristics and shapes will be described. First, the electrical resistance of the fiber is 10 ⁴ as an effective effect per fiber. -10 ¹⁰
Five prototypes in the range of ohm (Ω) / mm (mm). Ten prototypes with fiber thicknesses ranging from 0.5 to 30 denier.

The flocking density is 10 fibers / cm ² ~ 20,000 / cm
^Two In this experiment, brush fibers having a length of 2 to 15 mm were produced as appropriate, and transfer characteristics were examined by changing the pressing conditions (mainly the amount of bite) applied to the photosensitive drum 1. As a result, as a suitable condition for the above parameters, if the fiber length was 3 mm or less, it was difficult to adjust to satisfy the transfer characteristics.

If the fiber length is in the range of 3 to 10 mm, a fiber having an appropriate flexibility with a fiber thickness of about 1 to 10 denier is mechanically good, and the electrical resistance per fiber is 10 ^5. ~
10 ⁹ Good transfer characteristics were exhibited in the range of ohm (Ω) / mm (mm). In addition, fiber length 10-15mm
In this case, a material of about 3 to 15 denier showed a good result. Although the study is omitted, it is clear from the above results that the function can be achieved by appropriately selecting the length of the fiber even with a longer length. However, if the size is larger than this, the size of the apparatus is increased, and practical value is lost.

The density of planted hair (fiber / unit length) must be experimentally selected to determine the strength of pressing the paper against the photosensitive drum 1 together with the thickness and length. However, among these, it was found that the flocking density further has another important factor. That is, when the density is reduced in order to adjust the pressing force, an image missing portion called a transfer omission gradually occurs in the transferred image.

This is because the paper is charged due to local discharge caused by the voltage applied to the paper from the fiber tip during transfer, but the paper is not charged when the distance between the fiber tips is too large. It is understood that an image of this portion is missing without being transferred because a portion is generated.

The conditions for the occurrence of the transfer omission vary depending on the type of paper used for the transfer and the environmental humidity. However, in a normally used paper, at a relative humidity of about 30 to 70%, the fiber 15b It has been confirmed that when the distance between the tips is about 3 mm or less, it hardly occurs.

From the above, the order of determining the above factors is as follows: first, the density of the flocking is determined (preferably, the number of fibers is increased so as to be 2 mm or less), and then the thickness and length suitable for this are determined. You have to decide. Extracting the optimal transfer conditions from the above study results,

The average density of the tips of the fibers of the cylindrical brush 15 is about 3 fibers / mm or more (most preferably 500 to
1000 pieces / cm ² ), And as the thickness of the fiber, a fiber having an appropriate flexibility of about 1 to 15 denier (this is selected in relation to the length) is used. Resistance 10 ⁵ -10
⁹ By adjusting the conductivity so as to be in ohms (Ω) / mm (mm), the cylindrical brush 15 exhibiting appropriate transfer characteristics can be produced.

This transfer device 5 (fiber is 4 denier, length
7mm, 5000 fibers / cm^Two ) To the conventional conductive
Softness most suitable for a transfer roller using a
(JI 30 degrees) roller and trial transfer roller ratio
Comparison. Comparison of transfer brush and transfer rubber roller
The allowable width of the bite amount for the photosensitive drum 1, ie,
That is, the required machine precision was compared. Figure 3 shows the results
You. FIG. 3 shows a rubber roller and a cylindrical brush 15 on a spring ground.
Pressing and biting amount (pressing distance) and indicated value of tsubo (contact
(Value divided by length). Respectively
Roller is also actually experimenting with image transfer, and as a result
Is about 70-80 grams (g) / cm or more load
Transfer is missing.

Therefore, when these are superimposed on FIG. 3, when the transfer by the conventional rubber roller is performed, the mechanical digging amount at which an appropriate transfer can be performed is at most 0.1 ± 0.0.
The diameter of the cylindrical transfer brush 15 is about 5 mm.
Is about 0.7 ± 0.5 mm, which shows a mechanical tolerance of 10 times or more that of the conventional one, which contributes to the simplicity of component accuracy and position setting, and a setting that was a major obstacle in practical use with rubber rollers. It turns out that the problem of accuracy can be solved.

In order to maintain this level of mechanical accuracy, the support angle θ of the support member 15a of the transfer brush 15b with respect to the tangent line between the photosensitive drum 1 and the transfer brush 15b as shown in FIG.
By fixing to about 60 degrees, preferably about 5 to 30 degrees, the amount of bite (the amount of distortion), that is, the pressing force can be adjusted.

The outer diameter intersection of the cylindrical brush 15 is ± 0.1 mm
Since the degree can be easily made, the appropriate value can be easily maintained by providing a guide roller coaxially smaller than the outer diameter of the brush at both end portions of the cylindrical brush 15 if it has the above-mentioned allowable range. .

That is, in the transfer by the transfer brush using the elastic fiber as in the present embodiment, there is a great advantage that the transfer paper pressing force can be easily maintained at 70 g / cm or less which is optimal for the transfer.

The guide roller should be selected so that this load is preferably a median value (approximately 0.7 mm in this example) of a biting suitability value which differs depending on the material, thickness, density, length, etc. of the selected fiber. It is.

Such a contact-type transfer unit exhibits stable transfer characteristics even under humid conditions, and thus has the effect of reducing the amount of developer remaining after transfer to reduce the need for cleaning, and has the effect of reducing the amount of paper in the transfer paper. Since it also has a powder removing effect, it reduces the load on the cleaning device and contributes to improving reliability.
On the other hand, below the photosensitive drum 1, a paper feed unit 18 that supplies the paper 16 to the transport path 14 is provided. The paper supply unit 18 stores paper 16 as a material to which an image is to be transferred. Above the paper feed unit 18, the paper 1 is rotated from the paper feed unit 18 by rotation.
A paper feed roller 19 that supplies the sheet 6 to the conveyance path 14 is provided.

Further, at the end of the transport path 14, the paper 16
Is provided with a fixing device 20 for fixing the transferred toner image. A gate 31 is provided on the discharge side of the fixing device 20, and the rotation of the gate 31 allows the sheet P to be selectively discharged to the first or second discharge portion 32, 33 after development. Is transported to the next transfer area facing the transfer device 5 as described above. On the other hand, the paper 16 is sent from the paper supply unit 18 to the transfer area in synchronization with the rotation of the photosensitive drum 1 by the rotation of the paper supply roller 19. The back side of the paper 16 is charged to a positive polarity by the cylindrical brush 15. Therefore, the toner image on the surface of the photosensitive drum 1 is electrostatically attracted to the paper 16 and transferred.

Here, a voltage of 800 to 2,000 volts is applied to the rotating shaft of the cylindrical brush 15 by the DC power supply 21, and the cylindrical brush 1 is passed through the conductive tube 15 a.
A voltage is applied to the conductive fibers 15b on the surface of the fifth fiber 5. Since the cylindrical brush 15 is contaminated with toner or the like during use, cleaning is necessary for long-term use.

In the present embodiment, for this purpose, a metal roller 22 that is in sliding contact with the conductive fiber 15b is provided, and a voltage applied to the cylindrical brush 15 by a bias power supply 23 is applied thereto.
By applying a voltage higher by 00 to 200 volts, the toner of the conductive fibers 16b is removed. Further, the toner and the like adsorbed and collected by the metal roller 22 are favorably cleaned by the blade 24 and accumulated in the collection container. By this cleaning, the cylindrical brush 15 was able to maintain a good transfer function over 100,000 or more prints.

Also, the results of tests conducted by changing the relative humidity of the environment in the range of 30 to 80% show that, under an environment of about 70% or more, the transfer efficiency (transfer efficiency) is clearly higher than the corona transfer method. The ratio of the transferred toner to the amount of toner on the photosensitive member before transfer was high, and it was also confirmed that the toner was excellent.

As described above, the elastic conductive cylindrical brush 1
In the transfer by the transfer device 5 using the transfer device 5, the transfer device is not expensive, hardly generates ozone, and the transfer device can be easily cleaned. Since the transfer is continued and the paper 16 is in direct contact with the paper 16 at the time of the transfer, the paper dust adhering to the paper 16 can be efficiently absorbed and removed.
The attachments remaining on the cleaning device 5 are greatly reduced.
It has been confirmed that the burden on the user can be reduced.

Further, since the transfer device 5 has a large mechanical tolerance when mechanically pressing the paper 16, transfer omission (no partial transfer) is effectively prevented. However, when the thickness of the paper is large, the pressing force exceeds the allowable range, so that there is a restriction that a complicated countermeasure mechanism is required. However, in the transfer according to the present invention, the allowable range of the biting amount is large. Therefore, it is worth noting that the influence is small and a clear image is transferred regardless of the paper thickness.

In addition, as a material of the conductive fiber,
A resin using an acrylic resin or the like can be similarly used as long as it has appropriate flexibility, mechanical strength, dispersibility with carbon, and the like.

In the above-described embodiment, a rotary brush is used as an example. However, the present invention is not limited to this. For an apparatus using continuous paper or the like that reliably transports paper, a fixed brush is used. The same function can be exerted by contacting.

[0044]

As described above, according to the present invention,
Since the transfer is performed using the conductive plate member having elasticity, the image can be transferred without increasing the cost and generating almost no ozone.

Further, the mechanical tolerance when mechanically pressing the material to be transferred is large, and transfer omission is effectively prevented. In particular, in the case of the conventional roller transfer method, the thickness of the material to be transferred is reduced. When the thickness is large, the pressing force exceeds the allowable range, and there are restrictions such as a need for a complicated countermeasure mechanism. However, in the transfer according to the present invention, the allowable range of the bite amount is large,
The effect is that the influence is small and a clear image can be transferred regardless of the thickness of the material to be transferred.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a cylindrical brush of a transfer device according to one embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an image forming apparatus including the transfer device of FIG. 1;

FIG. 3 is a graph showing the relationship between the amount of biting of the cylindrical brush of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum (image carrier), 3 ... Image exposure apparatus (electrostatic latent image forming means), 4 ... Developing device (developing means), 15 ... Cylinder brush, 15b ... Conductive fiber.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-199365 (JP, A) JP-A-56-135864 (JP, A) JP-A-60-216361 (JP, A) JP-A-4- 215680 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/02

Claims (2)

(57) [Claims] A latent image forming means for forming an electrostatic latent image on the image carrier; and a developer for supplying a developer to the electrostatic latent image formed by the latent image forming means to form a developer on the image carrier. Developing means for forming an image; supply means for supplying a transfer material to the image carrier; and a conductive element provided rotatably in contact with the image carrier.
A transfer means for transferring a developer image formed by the developing means onto the transfer material, the transfer means having conductive fibers provided on a peripheral surface of the conductive element tube, and a transfer voltage applied to the transfer means; and a voltage applying means for supplying, said transfer means, 70 g / cm or less with respect to the image bearing member
And the distance between the fiber tips is
The fiber density should be 500 to 10 so that it is 3 mm or less.
00 fibers / cm ² , the thickness of the fiber is 1 to 15 deniers,
The length of the fiber is 3 to 15 mm and the conductive
A voltage is supplied from the voltage applying means to the sex tube.
Image forming apparatus, characterized in that the at it. 2. A latent image forming means for forming an electrostatic latent image on an image carrier, and a developer supplied to the electrostatic latent image formed by the latent image forming means to supply a developer on the image carrier. Developing means for forming an image; supply means for supplying a transfer material to the image carrier; and a conductive element provided rotatably in contact with the image carrier.
A transfer means for transferring a developer image formed by the developing means onto the transfer material, the transfer means having a tube and conductive fibers provided on a peripheral surface of the conductive element tube ; Coaxially provided at both ends of the raw tube
The outer diameter is smaller than the outer diameter of the conductive fiber.
Comprising a guide roller for pressure adjustment that, a voltage application means for supplying a transfer voltage to said transfer means, said transfer means, 70 g / cm or less with respect to the image bearing member
And the distance between the fiber tips is
The fiber density should be 500 to 10 so that it is 3 mm or less.
00 fibers / cm ² , the thickness of the fiber is 1 to 15 deniers,
The length of the fiber is 3 to 15 mm and the conductive
A voltage is supplied from the voltage applying means to the sex tube.
Image forming apparatus, characterized in that the at it.