JPH04208979A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a distinct image even in the case of consecutive printing by controlling electric field between a non-patterning member and a photosensitive body so that the charge amount of developer may be smaller than that of normal developer electrostatic charging polarity. CONSTITUTION:By allowing the brush 2a of a non-patterning means 2 to contact with a developer image which remains at the time of transferring and an electrostatic latent image, non-patterning is electrostatically and mechanically performed. Then, a photosensitive drum 1 reaches a developing and cleaning position again but residual developer is nearly uniformly and thinly scattered, so that irregularity in exposure does not occur. Since proper developing bias is impressed on a developing roller 10, the developer newly adheres to an exposing part from the roller 10 and simultaneously the residual developer adhering to a non-image area is attracted to the roller 10 to be recovered. It is good that the electrostatic charging amount Q of the developer in a developing device and the average electrostatic charging amount QA of the developer adhering to an image carrier after the developer passes a developer image non-patterning member satisfy the relation of 0.5XQ<=QA<-1.0XQ in the case that Q is negative polarity and 0.5XQ>=QA>-1.0XQ in the case that Q is positive polarity.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention forms a latent image on an image bearing member such as a photoreceptor, develops this latent image, and transfers the image onto a transfer medium such as paper. The present invention relates to an image forming apparatus for recording on a material.

(Prior Art) As this type of image forming apparatus, electrophotographic apparatuses, electrostatic printers, and the like are known. In these image forming apparatuses, after forming an electrostatic latent image on a photoreceptor, a developer is electrostatically attached to the electrostatic latent image to form a developer image, and then the developer image is transferred to a sheet of paper. It is recorded by transcribing it. In addition, since the electrostatic latent image and developer that has not been transferred remain on the photoreceptor after transfer, this residual developer is removed by a cleaning device, and then the electrostatic latent image is removed by a static eliminator. are doing.

Incidentally, in recent years, there has been a demand for downsizing of image forming apparatuses, and for example, Japanese Patent Application Laid-Open No. 11538/1983 describes a method for downsizing image forming apparatuses by using a single device as a developing device and a cleaning device. A cleanerless process is disclosed. In this method, in one developing device, the electrostatic latent image is developed when the photosensitive drum passes through the developing device for the first time, and then the residual image after the transfer is cleaned by passing through the developing device a second time. There is. However, in this conventional method, the residual image is removed when the photosensitive drum passes through the developing device for the second time, so the recording speed is halved and the circumference of the photosensitive drum is removed. There is a problem in that a recording area larger than the entire surface cannot be obtained, and the photosensitive drum must necessarily be made relatively large, making it impossible to make the device sufficiently small.

On the other hand, U.S. Patent No. 364926 discloses a developing device that simultaneously develops the electrostatic latent image and cleans the developer remaining after the previous transfer when the electrostatic latent image passes for the first time. A method is disclosed to overcome the drawbacks regarding speed by using the following method.

In this method, a transfer residual image non-patterning member is disposed between the transfer means and the image carrier charging means, which applies a bias to a conductive or electrically resistive member and non-patterns the transferred residual image. Accordingly, it is possible to prevent the occurrence of memory of untransferred developer remaining on the image carrier. (
Japanese Patent Publication No. 1986 (Problem to be solved by the invention) However, in this conventional image forming apparatus, when a high-density image is continuously printed, the non-patterning member that turns the transferred residual image into a non-pattern becomes dirty. As a result, the effect of preventing memory is weakened, resulting in problems such as memory images being generated, and developer accumulated on the non-patterned member scattering or falling, making it impossible to obtain clear images.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus that can obtain clear images even when printing is performed continuously.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes: an image bearing member; (20) an image exposure means for forming a latent image on the image bearing member; a developer cleaning means for supplying a developer to perform development and simultaneously removing the developer remaining on the image carrier; It is characterized by comprising a member that non-patterns the developer remaining on the photoreceptor, and the average charge amount Qa of the developer that has passed through the non-pattern member and is attached to the photoreceptor.
(μc/g) and the amount of charge Q (
μc/g) or satisfies the following equation (1) or (2).

When Q is negative polarity, 0.5×Q≦Qa≦−1.0×Q ・= (1) When Q is positive polarity, 0.5×Q≧Qa≧−1,0×Q−(2) Above It is preferable that the electric field formed between the image carrier and the developer image non-patterned member be in a direction in which charge is injected into the transferred residual developer image to have a polarity opposite to the normal developer polarity.

It is preferable that the electric field formed between the image carrier and the developer image non-patterned member be controlled so that it is stronger in at least a portion outside the print area than in the image area.

(Function) As shown in the relationship of formula (1) or formula (2) above, the amount of charge of the developer that has passed through the non-patterned member of the transferred residual image, or
The polarity of the developer charged on the developing cleaning means is opposite to that of the regular developer charging polarity.
Alternatively, by controlling the electric field between the non-patterned member and the photoreceptor so that the charged polarity of the developer is smaller than the normal developer charging polarity even if the polarity is the same, the residual image of the non-patterned developer by the non-patterned member is transferred to the developing and cleaning means. This allows sufficient cleaning. Therefore, an image can be obtained in which there is no memory image or image stain in the formed image, and there is no accumulation of developer on the non-patterned member and no developer drop or developer scattering occurs.

(Example) The present invention will be described below with reference to an example shown in the drawings.

FIG. 1 shows an image forming apparatus according to the present invention, in which a recording surface smaller than the area of the image to be recorded (that is, a small diameter) is provided as a photosensitive image carrier at approximately the center of the main body H. A body drum 1 is provided rotatably in the direction of arrow A. The photoreceptor drum 1 is made of an organic photoreceptor (OPC) type photoconductive material. Further, around the photosensitive drum 1, static eliminating means 7 are arranged sequentially along the rotation direction of the photosensitive drum 1.
, a transfer residual developer non-patterning means 2, a scorotron charger 3, a laser device 4, a developer cleaning device 5, and a transfer roller 6 are provided.

The residual developer non-patterning means 2 is 103 to 109.
It has a brush 2a made of fiber (trade name: Trading Card, Kynor, etc.) having an electrical resistance of Ω, and is arranged so as to be in sliding contact with the photoreceptor drum 1, and has an electrical resistance of +200 to 1
A voltage of 200 volts is applied. Further, the scorotron charger 3 charges the surface of the photoreceptor drum 1 by -4
It is designed to be negatively charged approximately uniformly between 50 and -800 volts.

The laser device 3 forms an electrostatic latent image on the charged area of the photosensitive drum 1 irradiated with a laser beam 8 on the surface of the photosensitive drum 1 according to image information to be recorded.

Further, in the developer cleaning device 5, a hopper 9 that stores a so-called one-component developer T that is triboelectrically conveys the developer T toward a position facing the photoreceptor drum 1. A developing roller 10 is provided for returning the developer T remaining in the hopper 1 into the hopper 9. A partially cutaway sectional view of this developing roller is shown in FIG. As shown in FIG. 2, the developing roller 10 includes a metal shaft 101, a conductive elastic layer 32 made of foamed urethane, silicone rubber, EPDM, etc. formed on the metal shaft 31, and a conductive elastic layer 32 formed on the metal shaft 31. 102~108Ωm on 32
A conductive surface layer 33 having an electrical resistance of
The roller is elastic as a whole.

An elastic blade 13 made of phosphor bronze, urethane, or silicone resin is pressed against the developing roller 10 for frictionally charging the developer T and forming a thin layer of developer with a predetermined thickness. , the developer T passing through here is charged with a negative triboelectric charge of the same polarity as the photoreceptor drum 1.
A thin developer layer of about 3 to 3 layers is formed.

The elastic blade 13 has a structure in which a silicon chip with a radius of 3 mm is mounted as the surface layer 11 on a phosphor bronze plate with a thickness of 0.15 mm, and this chip portion is pressed against the developing roller. Note that this surface layer 11 must be selected in consideration of frictional charging with the developer T and appropriate elasticity and frictional properties; for example, urethane resin mixed with 10 to 30 weight percent of conductive carbon is selected. It is formed by coating something. Further, a bias power source 14 is connected to the developing roller 10, and the elastic layer 12 and the surface layer 1 are connected to each other.
1, a predetermined development bias is applied during development and cleaning. A sponge-like developer conveying roller 15 is provided in the hopper 9, and plays the role of preventing agglomeration of the developer T in the hopper 9 and conveying and supplying the developer T.

The transfer roller 6 is moved substantially below the photoreceptor drum 1 through the paper conveyance path 16.
is provided facing the circumferential surface of the

The transfer roller 5 has the same structure as the developing roller 10, but the electrical resistance of the surface layer 11 is 10 5 to 10 10 Ω (maximum). The transfer roller 6 applies a voltage of 600 to 2,000 volts from the high voltage power supply 24 to the back side of the paper conveyed here, electrostatically attracts the developer, and transfers the developer image from the photoreceptor drum 1. Transfer to paper.

Such a contact type transfer means has the effect of reducing the amount of developer remaining after transfer and reducing the burden of cleaning so that it can exhibit stable transfer characteristics even under high humidity conditions.
It is also possible to remove paper dust from the transfer paper and prevent it from being mixed into the developer. The conductive brush 2a of the transfer residual developer non-patterning means 2 is brought into sliding contact with the rotation of the photosensitive drum 1,
A voltage of 200 to 1,500 volts is applied by connecting to a bias power source 23 to temporarily adsorb the developer remaining on the photosensitive drum 1 after transfer. Since most of the transferred residual developer has negative polarity, some of the transferred residual developer that is adsorbed by the residual transferred developer non-patterning means 2 or is a fogging developer is positively charged. The developer passes through without being adsorbed, but the amount is so small that it does not pose a problem. - Occasionally, the transferred residual developer temporarily adsorbed by the non-patterning means 2 is removed by the applied bias or the brush 2a.
A positive charge is injected within a period of time depending on the electrical resistance of the brush 2a, the particle size of the developer, the electrical resistance, etc., and the electric field formed between the brush 2a and the photosensitive drum 1 causes the photosensitive drum 1 to
be returned to. As described above, the time from when the residual developer is temporarily adsorbed by the residual developer non-patterning means 2 until it is returned to the photosensitive drum 1 after receiving charge injection depends on the particle size of the developer, Due to factors such as resistance, the distribution will have a certain range of width. When the developer non-patterning means 2 is used in this way, the untransferred developer is temporarily removed from the brush 2.
After being adsorbed by a, it is returned to the photoreceptor layer almost uniformly, so that the residual image due to the residual developer is non-patterned. In addition, the brush 2 is used to unpattern the residual developer after transfer.
The mechanical sweeping effect of a also contributes. However, when the density of the printed image is high, the amount of developer remaining after transfer inevitably increases, some of the developer is not re-adhered to the photoreceptor, and the developer gradually accumulates in the blank 2a.

The developer returned to the photoreceptor drum has a positive polarity that is opposite to the normal polarity, or when the photoreceptor drum 1 is charged by the Scorotron charger 3, it is exposed to negative corona and the developer also has a negative polarity. Then, it is cleaned in the developing and cleaning device 5.

Next, the resistance of the brush 2a will be described. If the resistance of the brush is too large, the responsiveness of the electric potential at the tip of the brush will be poor, and the time constant for the operation of adsorbing the developer, injecting the charge, and returning it to the photoreceptor will become large, which will cause non-responsiveness of the transferred residual image of the high-frequency line image. Problems may occur, such as insufficient patterning or insufficient return of developer to the photoreceptor, resulting in a large amount of developer accumulation. Furthermore, if the resistance of the brush 2a is too low, bias may leak to the photoreceptor, causing damage to the photoreceptor. Therefore, the resistance of the brush 2a is 10 to 1019
Ω is desirable. Furthermore, the photoreceptor drum 1 is also positively charged by the brush 2a, but the potential at this time varies depending on the amount of developer remaining after transfer, etc., so the charging device may be a scorotron charger as in this embodiment. desirable.

In this way, the temporary adsorption and sweeping out of the transfer residual developer is performed in a short cycle, so that only a small amount of developer remains on the brush 2a.

A conveying path 16 for paper P is placed below the photosensitive drum 1.
A paper feed unit 19 is provided for supplying paper to the paper. This paper feeding unit 19 stores a paper P to which an image is to be transferred. A paper feed roller 2o is provided above the paper feed unit 19 and supplies the paper P from the paper feed unit 19 to the transport path 16 by rotation.

The conveyance path 16 is provided with a fixing device 21 that fixes the transferred developer image onto the paper P, and fixes the developer image on the paper P using heat and pressure.

In the above-described apparatus, if continuous printing is performed without a process of discharging the developer accumulated on the brush 2a in the paper interval between prints, that is, without a dispensing mode, the developer that has been adsorbed at - The amount of developer gradually accumulates, and if it exceeds the allowable amount, problems such as scattering, a large amount of developer being swept away from the brush, and image defects may occur, and the residual image on the brush 2a may be removed. Problems such as reduced depatterning ability and memory image generation tend to occur. By arranging the transfer residual developer non-patterning means 2 above the photoreceptor drum 1 or toward the developing device from above, it is possible to prevent the developer T attached to the brush 2a from falling and scattering into the machine. can be reduced to some extent. However, when the amount of accumulated developer increases, there is a possibility that developer dropout or developer scattering may occur.

Next, the operation of the electronic copying apparatus according to this embodiment will be explained. The photoreceptor drum 1 is rotated in the direction of arrow A, and the circumferential surface of the photoreceptor drum 1 is charged approximately -4 by the scorotron charger 3.
Charges between 50 and 800 volts. Subsequently, this charged area is exposed by irradiating a laser beam 8 from the laser device 4,
An electrostatic latent image is formed on the surface of the photoreceptor drum 1. The electrostatic latent image is then conveyed to a developing cleaning position facing the developing cleaning device 5. The developer T is sent out from the developing roller 11 of the developing and cleaning device 5, and comes into contact with the electrostatic latent image elastically and with a contact width due to deformation, causing the developer T to adhere to the electrostatic latent image to form a developer image. In this case, the developer T adheres to the area irradiated with light, resulting in so-called reversal development. The developer T is approximately -5 to 30 μc/g (microcoulombs/g) due to friction between the blade 13 and the surface layer 11 of the developing roller 10.
The developing roller 10 is charged with about -150 to 4
A voltage of 50 volts is applied. The developer image after development is
Next, it is conveyed to a transfer area facing the transfer roller 6.

On the other hand, the paper P is fed to the transfer area from the paper feed unit 19 by the rotation of the paper feed roller 20 in synchronization with the rotation of the photosensitive drum 1 .

The back surface of the paper P is positively charged by the transfer roller 6. Therefore, the developer image on the surface of the photosensitive drum 1 is electrostatically attracted to the paper P and transferred.

Here, the transfer roller 6 is operated by a DC power source 23.
A voltage of 00 to 2,000 volts is applied to the rotating shaft, and a voltage of 105 to 109 Ω is applied to the roller surface through conductive parts made of silicone resin mixed with 5 to 40 weight percent of conductive carbon at both ends of the transfer roller 6. A voltage is applied to the conductive surface of the mark. In order to make it easier to clean the surface of the transfer roller 6 from foreign matter such as developer and paper powder, it is preferable to use a material that has a smooth surface and low friction.In this example, conductive polyfluoride resin is used. , conductive polyester, etc., and can be cleaned well with a cleaning blade. Further, as for the rubber hardness of the entire roller, a flexible one having a rubber hardness of 25 to 50 degrees according to comparative measurements according to the JIS method was found to have a wide tolerance for the pressing force of the transfer roller 6 against the photoreceptor drum 1 and to be good.

In a transfer method using a transfer roller, there is no dependence of transfer efficiency on the environment (especially humidity). On the other hand, in corona transfer,
Transfer efficiency decreases significantly in a humid environment.

This means that in an image forming apparatus without a cleaning device as in the present invention, the amount of residual developer after transfer increases rapidly under high humidity conditions. It is the biggest cause of defects.

From the above, the roller transfer method is very effective in cleanerless processes. By the way, a small amount of the developer image and electrostatic latent image that were not completely transferred remain on the surface of the photoreceptor drum 1 after the transfer. These developer images and electrostatic latent images are conveyed to the transfer residual developer non-patterning means 2 and are non-patterned. In the transfer residual developer non-patterning means 2, the brush 2a is brought into contact with the developer image and the electrostatic latent image to apply electrostatic and mechanical force to remove the remaining residual particles in fine, illegible condition as described above. Disturb the image. However, the effect of this non-patterned member differs depending on the potential of the photoreceptor. Therefore, if the electrostatic latent image on the photoreceptor remains, some places will be insufficiently patterned depending on where there is charge or where there is no charge. Therefore, the latent image is erased by the static eliminating means (red LED) located upstream of the non-patterned member. The developer T scattered on the surface of the photoreceptor drum 1 by the non-patterned member is distributed in the form of a sufficiently small mist, and no longer contains information in the form of characters or images.

Photosensitive drum 1 charged by Scorotron charger 3
After being charged, it is exposed to light by the laser device 4 to form an electrostatic latent image, and reaches the developing cleaning position facing the developing cleaning device 5 again (for the second time). In this case, in the electrostatic latent image formed the second time, the residual developer is almost uniformly and sufficiently distributed in the exposed areas (image areas to which the developer should adhere) and non-exposed areas (non-image areas). Since it is thinly scattered, there will be no uneven exposure. Therefore, even in the second development, the residual potential after exposure becomes uniform, so that a uniform developer image can be obtained. Here, as mentioned above, the developing roller 11 has a hardness of 30 to 70 according to the JIS rubber hardness measurement method.
Since it has an elasticity of 112 to 108 mm and a conductivity of 112 to 108 mm, a linear load of 20 to 150 mm is applied to the developing roller 10.
By applying a load of g/am and pressing and sliding contact with a speed difference of 1.5 to 4 times, a bump) is generated in the contact width of 1 to 4II11, and in this nip, the residual developer and the developing roller 10 Because the developer T on the top is agitated and rubbed,
A strong frictional force is generated and the cleaning ability is enhanced.

Moreover, since the developer is formed from only developer T,
There are no streaks or flaky deterioration in image quality. Furthermore, in the non-exposed area, since the suction force due to the developing bias exceeds that of the photosensitive drum 1, the attached developer T is successively attracted to the developing cleaning device 5 and collected. That is, the developing roller 10 is provided with a developing bias of an appropriate value between the residual potential of the exposed area and the potential of the non-exposed area (1150 in the embodiment).
By applying voltage (v~-450V), the developing roller 1
New developer adheres to the exposed area from zero, and at the same time, residual developer adhered to the non-image area (non-image area) is attracted from there to the developing roller 10 and collected. In this case, since the residual developer is small and has already been dispersed in the form of a small mist in the transfer residual developer non-patterning means 2, the developer cleaning device 5 can efficiently collect the residual developer. No defects will occur. In this way, the photoreceptor drum 1 is rotated and used redundantly,
- Obtain two recorded images.

As the transfer method, it is preferable to use a transfer roller as in the embodiment, but even if a corona transfer method is used, there is no problem in practical use.

After development and cleaning, the developer image is transferred to the transfer roller 6.
The image is transferred to the paper P at the position facing the . Thereafter, similar steps are repeated.

In order to temporarily adsorb the transfer residual developer and inject charge,
In the embodiment, a DC bias with a polarity opposite to that of the developer is applied to the brush 2.
is applied to a. Much of the developer temporarily adsorbed (trapped) by the brush 2a re-adheres to the photoreceptor drum 1, but some of the developer is not completely re-adhered, and as mentioned above, all the adsorbed developer is not discharged and only a small amount remains on the brush. Some things stop.

Therefore, when high-density images are continuously printed, the developer gradually accumulates on the brush 2a, which tends to cause memory erasure failure or developer dropping from the brush.

Therefore, in order to prevent the developer from accumulating on the brush 2a, in this embodiment, an operation (discharge mode) is performed to discharge the developer accumulated on the brush 2a at the paper interval between prints. Specifically, this is achieved by turning off the transfer means and the static elimination means at the paper interval. In the image area during printing operation, the photoreceptor potential when the brush reaches it is reduced by static electricity removal before the brush.
The potential is adjusted to approximately -50 to -100V.

A DC bias of +500V is applied to the brush, and most of the residual developer temporarily adheres to the brush due to the electric field of the brush photoreceptor, and then receives charge injection from the brush, reverses its polarity, and immediately ( Many developers are several liters
After 115eC to several 115eC), it re-deposit on the photoreceptor. However, if high-density images are continuously printed, sufficient charge injection and re-deposition will not occur, and developer will gradually accumulate on the brush, resulting in developer dropout, dirt inside the machine, and a decline in the brush's non-patterning ability. A problem occurs. Note that a DC bias of +700 cm is applied to the brush for the non-image area during the printing operation.

Therefore, in the area between the sheets, if the transfer is turned off and the pre-brush static elimination is turned off, the photoreceptor potential when it enters the brush is approximately -450 to -800, which is close to the photoreceptor charging potential.
The potential is as follows. At this time, the electric field on the brushless photoreceptor is stronger than in the image area, and since there is no developer remaining after transfer in this area, the developer that was stuck on the brush without being able to re-adhere to the photoreceptor in the image area is removed. Charge is injected by the brush, the polarity is reversed, and the material is reattached to the photoreceptor. In this way, sufficient charge is injected into the developer and redeposited onto the photoreceptor for each print, so that the developer does not accumulate on the brush.

Photoreceptor charging potential -600v, development bias -320v,
Transfer roller bias +1200V, transfer bias off at paper interval, static neutralization off before brush, brush bias +500
Under the condition v, on a chart with a black area of 15%, 2
When a 0,000-sheet print test was conducted, there was almost no accumulation of developer on the brush, and no problems such as developer falling or scattering occurred. At this time, the amount of charge of the developer inside the developing machine is -21,0 μC/Z, the amount of charge of the developer that has re-adhered to the image area is approximately +8,0 μC/g, and the amount of charge of the developer that has re-adhered to the image area is approximately +8,0 μC/g. The amount of charge is approximately +11.5μ
c/g.

Here, the amount of charge of the developer inside the developing device is the amount of charge of the thin layer of developer formed on the developing roller measured using the suction method, and the amount of charge of the toner attached to the photoconductor is also measured using the suction method. It was measured at A method for measuring the amount of charge using the suction method will be described later.

In this example, charge injection from the brush was used to redeposit the developer onto the photoconductor, but it is also possible to reattach the developer from the brush to the photoconductor by reversing the brush bias at paper intervals and setting it at about -250V. It can be attached. but,
In this case, the discharged developer was not sufficiently cleaned by the developing device, and image stains (fogging) occurred in the next print. At this time, the amount of charge of the developer attached to the photoreceptor was -27.2 μc/g. Next, when the brush bias at the paper interval was set to about -100 V, the discharged developer was not sufficiently cleaned, and the image was slightly smudged. At this time, the amount of charge of the developer after passing through the brush was -23.2 μC/g. The above results are summarized in Table 1 together with the case where charge injection from a brush was used.

The amount of charge of the developer redeposited on the photoreceptor differs depending on the method of redepositing the accumulated developer, and furthermore, the amount of charge of the developer shifts to negative polarity when exposed to a charged corona. In order for this developer to be cleaned in the developing device, the polarity of this developer must be the normal polarity (negative polarity), or
If the amount of charge is too large, cleaning will be insufficient.

Therefore, we conducted an experiment as shown below. The experimental apparatus is shown in Figure 3. A scorotron charger 100 provided on the photoreceptor 103 charges the photoreceptor to approximately -650V. 101 provided downstream thereof is a one-component developing device (similar to the developing and cleaning device 5 shown in FIG. 1), and 102 is a two-component developing device for attaching developer.

By putting various developers into the developing device 102 and applying various developing biases, it is possible to attach developers with various amounts of charge to the photoreceptor drum 103. A static eliminating lamp 104 is disposed between the developing cleaning device 101 and the developing device 102 for adhering developer, and the potential of the photoreceptor is neutralized to about -50V. The amount of charge of the developer inside the developing cleaning device 101 (actually on the roller) is -21,0 μc/g, and the developing bias is -320 μc/g.
It is V. Under the above conditions, the developing device 102 for developer attachment
A point B is provided between the scorotron charger 100 and the developing cleaning device 101, and a point C is provided between the developing cleaning device 101 and the static elimination lamp 104, and as a developer,
Approximately 10 types are used, from positive to negative polarity, and the amount of charge at point A QA (μc/g),
Charge amount QB at point B after passing through the charger (μc /
g), point C after passing through the developing cleaning device 101
The amount mc of developer attached to the photoreceptor was measured at (■/cd). At this time, the applied bias of the adhesion developing device 102 is such that the amount of adhesion developer at point A is approximately 0.2 (mg/
CD). The amount of developer attached to the photoreceptor and the amount of charge were measured by the suction method described below. The amount of developer adhered and the amount of charge were measured by this suction method using the apparatus shown in FIG. 4 in the following procedure.

■Remove the photoconductor 40 from the apparatus and measure the mass using an electronic balance: ml (+r) Measure the charge escaping from the tube.

:Qp(μC) ■Measure the mass of the photoreceptor after suction.

: m2 (g) At this time, the adhesion amount m (■/C-) and the adhesion developer charge tQ (μc/g) are calculated as follows.

m= (ml-m2)/5 Q-Qp/ (ml-m2) The amount of charge of the developer in the one-component developing device can also be measured by sucking the thin layer of developer formed on the roller using the above method. I can do it.

As a result of the experiment, the charge amount QA at point A and the adhesion amount m at point C with respect to the charge amount QB at point B. A graph showing the relationship between the two is shown in FIG. The area 200 in FIG. 5 is within the practical range, and image defects such as print stains do not occur. As shown in Figure 5, mc or 0
．． If it is less than 0.04 mg/c-, print stains will not occur, so it is sufficient if QB is approximately in the range of -9 to -30 (μc/g). It can be seen that in order to obtain such a QB, the QA should be approximately in the range of +20 to -10 μc/g. Therefore, the charge amount Q of the developer on the developing cleaning device 101 is -21,0ttc/
g, the formula 0.5×Q≦QA≦−1.0×Q holds true.

The value of QB is determined by the amount of charge that the developer is exposed to in the charged corona changes when the charging potential of the photoreceptor changes, but as a result of experiments under various conditions, the amount of charge Q of the developer in the developing device for cleaning the developer changes. On the other hand, it was found that sufficient cleaning was performed when the value of QB was in the range of 0J×Q to 1.5×Q. In order to satisfy the above conditions, the photoreceptor potential must be -450v~
When used at around 750v, the QA value is -1.0
It can be seen that the range of xQ to 0.5xQ is sufficient. In an actual device, the amount of charge on the developer after passing through the brush is smaller than the amount of charge on the developing device, and it is desirable that the polarity be reversed.

Taking these things into consideration, the developer used in the present invention is determined based on the amount of charge Q of the developer in the developing device and the amount of developer attached to the image carrier after the developer image has passed through the non-patterned member. The average charge amount Qa of the agent is expressed by the following formula 4% (2) When Q is negative polarity, 0.5×Q≦QA≦−1.0×Q (1) When Q is positive polarity, 0. 5×Q≧QA≧−1.0×Q…Limited to the range of (2).

In the embodiment, this is achieved by using charge injection from a brush with a DC bias, but it has been found that good results can be obtained even if an appropriate AC bias is superimposed on C.

In addition, when re-adhering the developer to the photoreceptor by reversing the brush bias at paper intervals, the developer cleaning device removes static electricity from the developer (or slightly charges it) using a weakly positive corona, and the developer cleaning device cleans it thoroughly. You can also.

In addition, in the embodiment, the explanation was made using the transfer roller 6.
The function is the same even if a corona transfer type transfer means is used.
Other known transfer means can be used.

In addition, in the embodiment, as an example of a developing cleaning device,
Although the method is not limited to a one-component development method, it is also possible to use other known two-component development methods, magnetic component brush method, fur brush method, cascade method, etc. Not even.

In addition, as an example of a means for non-patterning the transferred residual developer, a method using a conductive or resistive brush has been described, but conductive or resistive rollers, sponges, rubber, cloth-like members, etc. may also be used. A similar effect can be obtained.

That is, the present invention provides an electrostatic latent image forming means for forming an electrostatic latent image on an image bearing member, and a developer charged to the same polarity as the electrostatic latent image to be supplied to the image bearing member while performing reversal development. a developer cleaning means for removing developer remaining on the image carrier, a transfer means for transferring the developer image formed on the image carrier to a transfer target member, and a transfer residue remaining on the image carrier after transfer. In an image forming apparatus having a developer image non-patterning member that is in sliding contact with the developer and applies a voltage to non-pattern the transferred developer image, the average charge of the developer after passing through the developer image non-patterning member By satisfying the relationship expressed by the above formula (1) or (2) between the amount QA and the amount Q of developer charge inside the developing device, there is no accumulation of developer on the non-patterned developer member, and image stains and dirt are prevented. It is possible to perform good printing without memory.

[Effects of the Invention] As explained above, according to the present invention, in an image forming apparatus having a means for non-patterning the transfer residual developer remaining on the image bearing member, the transfer residual developer non-pattern forming means By suitably controlling the polarity and charge amount of the developer reattached to the photoreceptor, it is possible to prevent image staining, image memory, and developer dropping and scattering from the non-patterned member. In this manner, according to the present invention, it is possible to provide a smaller image forming apparatus that can obtain clear images even when printing is performed continuously.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the image forming apparatus of the present invention, FIG. 2 is a partially cutaway sectional view showing an example of the developing roller used in the present invention, and FIG. 3 shows the amount of developer adhered on the photoreceptor. FIG. 4 is a schematic diagram showing an experimental device for measuring the amount of developer charge; FIG.
FIG. 5 is a graph showing the relationship between the amount of developer attached and the amount of charge of the developer at each point on the photoreceptor. DESCRIPTION OF SYMBOLS 1... Photosensitive drum (image carrier), 2... Transfer residual image non-patterning means, 4... Development cleaning device (development cleaning means), 7... Static elimination lamp, 6... Transfer Roller (transfer means), T...developer, 10...developing roller (elastic developing member), P...paper (transferring material). Figure 2 Figure 3

Claims (1)

[Scope of Claims] Forming means for forming an electrostatic latent image on an image carrier, and supplying a developer charged to the same polarity as the latent image to the latent image formed by the latent image forming means. a developer cleaning means for simultaneously performing reversal development and removing developer remaining on the image carrier; In an image forming apparatus having a developer image non-patterning member that comes into sliding contact with a transferred residual developer image to non-pattern the transferred residual developer image, after the developer image has passed through the developer image non-patterned member. The average charge amount Q_A of the developer attached to the image carrier (μc/g
) and the amount of charge Q (μc/g) of the developer on the developing cleaning means
However, when Q is negative polarity, 0.5×Q≦Q_A≦−1.0×Q...(1) When Q is positive polarity, 0.5×Q≧Q_A≧−1.0×Q・・- An image forming apparatus characterized by satisfying the relationship (2).