JP2001281970A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a defective image caused by scattering toner, for example, that the scattering toner sticks to an exposure device. SOLUTION: Magnetic particles 2b magnetically restricted on the surface of a magnetic roller 2a is forced to come into slidable contact with the surface of the photoreceptor drum 1, and also the electrifying bias is applied so as to electrify the surface of the photoreceptor drum 1. As for the cleaner-less image forming device not equipped with a dedicated cleaning device, the toner remaining after transfer is caught by a magnetic brush electrifier 2 and toner- scattering is prevented by a scattering preventing member 13. If the accumulated quantity of the scattering toner is increased, catching performance of the scattering toner is reduced, then the scattering toner is shaken off by vibrating the toner by a cam 14 at proper time intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine and a printer which forms a toner image with toner.

[0002]

2. Description of the Related Art Conventionally, many image forming apparatuses using an electrophotographic system or an electrostatic recording system have been devised. FIG. 7 shows an example.

In the image forming apparatus shown in FIG. 1, when an image formation start signal is input, a photosensitive drum 1 is charged by a charger 2 to a predetermined potential. On the other hand, platen 1
An original reading lamp 9, a short-focus lens array, a CCD sensor, and the like are integrated into an image reading unit 9 for the original G placed on the original G, and the original G is scanned while being illuminated. The light reflected from the original surface of the scanning light is imaged by the short focus lens array and is incident on the CCD sensor. The CCD sensor includes a light receiving unit, a transfer unit, and an output unit. The light signal is converted into a charge signal in the CCD light receiving unit, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with the clock pulse. The output unit converts the charge signal into a voltage signal, amplifies the signal, reduces the impedance, and outputs the voltage signal. The obtained analog signal is subjected to well-known image processing, converted into a digital signal, and sent to a printer unit. In the printer unit, the laser exposure unit 3 that scans the light of the solid-state laser element that emits light ON and OFF in response to the image signal by a rotating polygon mirror that rotates at a high speed corresponds to the surface of the photosensitive drum 1 so as to correspond to the original image. Irradiation with light L forms an electrostatic latent image.

Next, the electrostatic latent image is developed by a developing device 4 containing a so-called two-component developer having toner particles and carrier particles.
To form a toner image on the photosensitive drum 1.

[0005] The toner image formed on the photosensitive drum 1 in this manner is electrostatically transferred onto the recording material P by the transfer device 5. Thereafter, the recording material P is electrostatically separated and conveyed to the fixing device 7, where it is thermally fixed to output an image.

After the transfer of the toner image, the residual toner (transfer residual toner) is removed from the photosensitive drum 1 by cleaning of the cleaning device 16, the charge is removed by the pre-exposure device 17, and the preparation for the next image forming process is performed.

In recent years, as shown in FIG. 1, a cleanerless device has been developed in which the cleaning device 16 is detached and the developing device 4 performs simultaneous development and cleaning. The simultaneous cleaning with development is a method in which the transfer residual toner remaining on the photosensitive drum 1 after the transfer is collected by the developing device 4 by the fogging bias at the time of the development in the next and subsequent steps. As a result, the transfer residual toner is collected and used after the next step, so that waste toner can be eliminated. In addition, there is a great advantage in terms of space, and it is possible to significantly reduce the size of the entire apparatus.

Further, since the photosensitive drum 1 has advantages such as low ozone and low electric power, a contact charging device, that is, a photosensitive member to which a voltage is applied is brought into contact with the photosensitive drum 1 as a charging member of the photosensitive drum 1. A device for performing the charging of item (1) has been put to practical use.

As a charging member of this type, a magnetic brush type is preferably used from the viewpoint of stability of charging contact. In the contact charging device of the magnetic brush type, conductive magnetic particles are directly magnetically restrained on a magnet or a sleeve containing a magnet, and are brought into contact with the photosensitive drum 1 in a stopped state or while rotating, and a voltage is applied thereto. The photosensitive drum 1 is charged by the application.
A brush formed of conductive fibers (hereinafter referred to as a "fur brush") or a conductive rubber roller formed of a conductive rubber in a roll shape is also preferably used as a contact charging member.

In particular, a normal OPC photosensitive member (organic optical semiconductor) is used as the photosensitive drum 1 using such a contact charging member.
When a surface layer having conductive fine particles dispersed thereon or an amorphous silicon photoreceptor is used, a charging potential substantially equal to the DC component of the bias applied to the contact charging member can be obtained on the surface of the photosensitive drum 1. it can.

The charging method for directly injecting charges into the surface of the photosensitive drum 1 is called "injection charging". This injection charging does not use a discharge phenomenon such as a corona charger when charging the photosensitive drum 1, so that ozone-less charging with low power consumption can be performed.

Reference numerals not described in FIG. 7 will be described later with reference to FIG.

[0013]

However, in an image forming apparatus having no cleaning device as described above, when the photosensitive drum is charged by the contact charger, toner scattering occurs during charging, and the vicinity of the contact charger is caused. For example, there is a possibility that the laser exposure means and the like disposed in the above-mentioned area may be stained.

In order to prevent such contamination by the scattered toner, the scattered toner must be prevented from reaching other members.
For example, a means for preventing toner scattering by contacting a brush-like scattering toner shielding means (scattering prevention member) with the surface of the charged photosensitive drum 1 is known.

However, since the amount of the scattered toner continues to increase due to the repetition of the image formation, the scattered toner shielding means may become dirty, preventing the scattered toner from being completely prevented and causing an image defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances, and is intended to prevent image accumulation due to scattered toner and prevent image defects caused by scattered toner. It is intended to provide a device.

[0017]

According to a first aspect of the present invention, there is provided a contact charging device for charging a surface of an image carrier, and an electrostatic latent surface on the surface of the image carrier after charging. A latent image forming unit for forming an image, a developing unit for attaching toner to the electrostatic latent image to develop the toner image as a toner image, and a transfer unit for transferring the toner image on the image carrier to another member In the image forming apparatus, a scattered toner shield is disposed downstream of the contact charging unit along a moving direction of the surface of the image carrier to prevent scattered toner from the contact charging member from scattered downstream. And vibration applying means for vibrating the scattered toner shielding means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the vibration applying means determines at least one of a vibration frequency and an amplitude of the vibration applied to the scattered toner shielding means by image forming. It is changed according to the number of continuous sheets of recording material to be passed.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the vibration applying means determines at least one of a frequency and an amplitude of vibration applied to the scattered toner shielding means by an image forming apparatus. It is changed according to the image ratio of the image to be performed.

The present invention according to claim 4 is based on claims 1, 2,
Or the image forming apparatus according to item 3, wherein the vibration imparting unit includes:
The scattering toner shielding means has a frequency of 0.1 to 100H.
giving a vibration in the range of z.

The present invention according to claim 5 is based on claims 1, 2,
Or the image forming apparatus according to item 3, wherein the vibration imparting unit includes:
A vibration having an amplitude in the range of 0.1 to 10 mm is applied to the scattering toner shielding means.

The present invention according to claim 6 is based on claims 1, 2,
Or the image forming apparatus according to item 3, wherein the vibration imparting unit includes:
A frequency of 0.1 to 10 Hz is applied to the scattering toner shielding means.
The vibration is given in the range of

The present invention according to claim 7 is based on claims 1, 2,
Or the image forming apparatus according to item 3, wherein the vibration imparting unit includes:
A vibration having an amplitude in the range of 0.1 to 3 mm is applied to the scattering toner shielding means.

The present invention according to claim 8 is the invention according to claims 1, 2,
3, 4, 5, 6, or 7, wherein the contact charging means is a magnetic brush charger having a magnetic brush on its surface that contacts the image carrier.

The present invention according to claim 9 is based on claims 1 and 2,
The image forming apparatus according to any one of 3, 4, 5, 6, and 7, wherein the contact charging means has conductive fibers on its surface, which are in contact with the image carrier.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a so-called cleaner-less image forming apparatus having no dedicated cleaning device.

Here, since the image reading unit 9 and the laser exposure means 3 as the latent image forming means are the same as those in the prior art, the same reference numerals are given and the duplicated explanation is omitted.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier.

The contact charging means is a magnetic brush charger 2 using a magnetic carrier. The magnetic brush charger 2 is shown in FIG.
As shown in FIG. 5, the magnet roller 2a is driven to rotate in the direction of the arrow, and the conductive magnetic particles 2b
Is directly magnetically constrained, and the surface of the photosensitive drum 1 is rubbed by the magnetic particles 2b. A charging bias in which a DC voltage is superimposed on an AC voltage is applied to the magnet roller 2a by a charging bias application power supply 2c. The magnet roller 2a may be stopped, and the magnetic brush charger may be configured to restrain the magnetic particles on the surface of a sleeve containing the magnet roller instead of the above-described configuration.
Further, as the contact charging means, instead of the above-described magnetic brush charger 2, a brush formed of conductive fibers (fur brush) or a conductive rubber roller formed of conductive rubber in a roll shape is also a contact charging member. Can be preferably used.

The magnetic carrier for charging has an average particle diameter of 10 to 100 μm and a saturation magnetization of 20 to 250 emu /
cm ³ , volume resistivity 1 × 10 ² to 1 × 10 ¹⁰ Ω · cm
Is preferable, and considering that there is an insulation defect such as a pinhole on the surface of the photosensitive drum 1, 1 × 1
0 it is preferable to use a ⁶ Omega · cm or more. In order to improve the charging performance, it is better to use a material having as small a resistance as possible.
Magnetic particles having a thickness of 5 μm, a saturation magnetization of 200 emu / cm ³ , and a volume resistivity of 5 × 10 ⁶ Ω · cm were used. The magnetic carrier for charging used in the present embodiment is obtained by oxidizing and reducing the ferrite surface to adjust the resistance.

Here, as the photosensitive drum 1 used in the present invention, a commonly used OPC photosensitive member (organic optical semiconductor) or the like can be used, but it is preferable that the OPC photosensitive member has a low volume efficiency. When a material having a surface layer having a material of 10 ² to 10 ¹⁴ Ω · cm or an amorphous silicon photoreceptor is used, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. Further, the chargeability can be improved.

Therefore, in this embodiment, the following first to fifth five layers are provided in order from the inside (from the bottom) on an aluminum drum substrate having a diameter of 30 mm, which is an OPC photosensitive member having a negative charge characteristic. The photosensitive drum 1 was used.

The first layer is a subbing layer, and is a conductive layer having a thickness of 20 μm provided for smoothing defects or the like of an aluminum substrate (hereinafter referred to as “aluminum substrate”).

The second layer is a positive charge injection preventing layer, which serves to prevent the positive charge injected from the aluminum substrate from canceling the negative charge charged on the surface of the photoreceptor, and comprises an amylan resin and methoxymethylated nylon. 1 × 10 ⁶ Ω
This is a medium-resistance layer having a thickness of 1 μm and a resistance adjusted to about cm.

The third layer is a charge generation layer, and is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin.
Exposure generates positive and negative charge pairs.

The fourth layer is a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.

The fifth layer is a charge injection layer, and is a coating layer of a material in which ultrafine SnO ₂ particles are dispersed in a binder of an insulating resin. More specifically, a material in which SnO ₂ particles having a particle diameter of about 0.03 μm, in which the resistance is reduced (conducted) by doping antimony which is a light-transmitting insulating filler into an insulating resin, is dispersed in the resin at 70% by weight. It is a coating layer. The coating solution thus prepared was applied to a thickness of about 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, beam coating method, etc. to form a charge injection layer. The surface resistance is 10 ¹³ Ω · cm. By controlling the surface resistance in this manner, the chargeability is directly improved and a high-quality image can be obtained. The photoreceptor is not limited to the OPC, but can be realized by an a-Si drum, and can achieve higher durability.

Here, the volume resistance of the surface layer is a value measured by arranging metal electrodes at an interval of 200 μm, flowing a preparation liquid for the surface layer between the electrodes to form a film, and applying a voltage of 100 V between the electrodes. It is. The measurement is a value measured under the conditions of a temperature of 23 ° C. and a humidity of 50% RH.

Next, the developing step will be described.

In general, the developing method is such that a non-magnetic toner is coated on a sleeve with a blade or the like, and a magnetic toner is coated by a magnetic force, conveyed and developed in a non-contact state with a photosensitive drum (one component) Non-contact development), a method of developing the toner coated as described above in contact with the photosensitive drum (one-component contact development), and a method in which a magnetic carrier is mixed with toner particles as a developer. And a method in which the toner is conveyed by magnetic force and developed in contact with the photosensitive drum (two-component contact development), and a method in which the two-component developer is developed in a non-contact state (two-component noncontact development) Broadly classified into types. The two-component contact development method is often used from the viewpoints of high image quality and high stability.

FIG. 3 is a schematic view of a developing device 4 for two-component magnetic brush development used in the present embodiment. The developing device 4 has a developing sleeve 4a in a developing container 4f, and a magnet roller 4b is fixedly arranged in the developing sleeve 4a. Stirring screws 4c and 4 are provided on the rear side (the right side in the figure) of the developing sleeve 4a, and a thin layer of developer is formed on the surface of the developing sleeve 4a above the developing sleeve 4a. Regulating blade 4a is disposed. A developing bias applying power source 4g is provided between the photosensitive drum 1 and the developing sleeve 4a. At least at the time of development, the developing sleeve 4 a has a region closest to the photosensitive drum 1 by about 500.
μm, and is set so that development can be performed in a state where the developer contacts the photosensitive drum 1.

In the two-component developer used in the present embodiment, toner particles obtained by externally adding 1% by weight of titanium oxide having an average particle diameter of 20 nm to a negatively charged toner having an average particle diameter of 6 μm are used. The magnetic carrier used was a magnetic carrier having a saturation magnetization of 205 emu / cm ^{3 and} an average particle diameter of 35 μm. A mixture of this toner and a magnetic carrier for development in a weight ratio of 6:94 was used as a developer. At this time, the toner in the developer has a triboelectric charge amount of about 25.
× 10 ^-3 C / kg.

Here, the electrostatic latent image is transferred to the developing device 4 described above.
The developing step of visualizing the image by the two-component magnetic brush method using the method and the circulation system of the developer will be described below. First, the developer pumped at the N2 pole with the rotation of the developing sleeve 4a is transported from the S2 pole to the N1 pole,
It is regulated by a regulating blade 4e arranged perpendicular to the developing sleeve 4a, and a thin layer is formed on the developing sleeve 4a. Here, the developer formed as a thin layer is the developing main electrode S
When conveyed to one pole, ears are formed by magnetic force. The electrostatic latent image is developed by attaching toner to the electrostatic latent image using the developer formed in the spike shape.
Due to the repulsive magnetic field of the pole, the developer on the developing sleeve 4a is
It is returned into the developing container 4f.

A DC voltage and an AC voltage are applied to the developing sleeve 4a from a developing bias applying power source 4g (not shown). In this embodiment, the DC voltage is -480V, the AC voltage is a peak-to-peak voltage Vpp = 1500V, and the frequency Vf = 3000 Hz is applied. In general, in the two-component developing method, when an AC voltage is applied, the developing efficiency is increased, and the quality of the image is high. On the contrary, fogging is likely to occur. For this reason, usually, the developing device 4
By providing a potential difference between the DC voltage applied to the photosensitive drum 1 and the surface potential of the photosensitive drum 1, fog can be prevented. The potential difference for preventing fog is called a fog removal potential (Vback), and the potential difference prevents toner from adhering to a non-image area during development.

This toner image is then transferred to a recording material (other member) P by the transfer device 5 shown in FIG. The transfer device 5 suspends an endless belt 5a between a driving roller 5b and a driven roller 5c, and is rotated in a direction indicated by an arrow in FIG. Further, a transfer charging blade 5d is provided in the transfer device 5. The transfer charging blade 5c generates a pressing force from the inside of the belt 5a toward the photosensitive drum 1, and is supplied with power from a high-voltage power supply to supply the recording material P. The toner images on the photosensitive drum 1 are sequentially transferred to the upper surface of the recording material P by performing charging of the polarity opposite to that of the toner from the back side of the toner image.

Here, the recording material P is conveyed by the paper feed roller 6a of the feeding / conveying device 6, is temporarily stopped by the registration roller 6b, and thereafter is stopped by the registration roller 6b.
The photosensitive drum 1 and the belt 5a are conveyed at a proper timing in synchronization with the rotation of the photosensitive drum 1 to a transfer section formed by the belt. In the present embodiment, the belt 5a
A film made of a polyimide resin having a film thickness of 75 μm was used. The material of the belt 5a is not limited to a polyimide resin, but may be a polycarbonate resin, a polyethylene terephthalate resin, a polyvinylidene fluoride resin, a polyethylene naphthalate resin, a polyetheretherketone resin, a polyethersulfone resin, a polyurethane resin, or the like. Plastic, fluorine-based, or silicon-based rubber can be suitably used. The thickness is not limited to 75 μm, but is 25 to 2000 μm.
m, preferably 50 to 150 μm, is suitably used.

Further, a transfer charging blade 5d having a resistance of 1 × 10 ⁵ to 1 × 10 ⁷ Ω was used. The transfer was performed by applying a transfer bias of +10 to 15 μA to the transfer charging blade 5d under constant current control.

Thus, the toner image formed on the photosensitive drum 1 is electrostatically transferred onto the recording material P by the transfer charging blade 5d. Thereafter, the recording material P is conveyed to the fixing device 7, is thermally fixed by the fixing roller 7 a and the pressure roller 7 b, and is then discharged onto the paper discharge tray 8.

On the other hand, the transfer residual toner remains on the surface of the photosensitive drum 1 after the transfer of the toner image. If the transfer residual toner is allowed to pass through the charger as it is, a phenomenon in which the charged potential is reduced only in the residual image portion, or a phenomenon in which the previous image portion becomes thin or dark on the next image, that is, a so-called ghost occurs. Magnetic brush charger 2 in contact with photosensitive drum 1
In most cases, the shape of the previous image remains unchanged even if the transfer residual toner passes below the area. Therefore, it is necessary to remove the transfer residual toner that has reached the charged area into the magnetic brush charger 2 with the rotation of the photosensitive drum 1 and erase the history of the pre-image. At this time, applying the DC voltage to the magnetic brush charger 2 does not sufficiently take in the toner into the charger, but applying the alternating voltage to the magnetic brush charger 2 causes the photosensitive drum 1 and the magnetic brush charger to be charged. The vibration effect of the electric field between the magnetic brush charger 2 and the magnetic brush charger 2
The toner can be easily taken in. Here, the transfer residual toner on the photosensitive drum 1 often has both positive and negative polarities due to peeling discharge at the time of transfer. Considering this, it is desirable that the transfer residual toner is positively charged.

In this embodiment, as shown in FIG. 2, the conductive brush 11 is brought into contact with the photosensitive drum 1 between the transfer device 5 and the magnetic brush charger 2, and a bias having a polarity opposite to the charging bias is applied. I do. The transfer residual toner of the positive polarity passes through the magnetic brush charger 2, and the transfer residual toner of the negative polarity is temporarily captured by the conductive brush 11, and is sent out onto the photosensitive drum 1 again after the charge is removed. As a result, the transfer residual toner is more easily taken in the direction of the magnetic brush charger 2, and it is possible to prevent the occurrence of poor taking. In order to prevent toner scattering from the magnetic brush charger 2, a brush-like scattering prevention member (scattering toner shielding means) 13 is brought into contact with the photosensitive drum 1 as shown in FIG. The scattering prevention member 13
Since the photosensitive drum 1 is arranged so as to be in contact with the charged photosensitive drum 1, the photosensitive drum 1 is normally not grounded (float) so as not to impair the charged state of the photosensitive drum 1.

Here, when the image forming operation is continued or a high-density image is formed, a large amount of scattered toner accumulates in the scatter prevention member 13 and the scatter cannot be prevented, resulting in an image defect. Would.

Therefore, in the present embodiment, the scattering prevention member 1
Micro-vibration was applied to 3 to prevent the scattering toner from accumulating on the scattering prevention member 13. Hereinafter, embodiments will be described in detail.

FIG. 4 is a side view of a scattering prevention member showing such an embodiment. When a cam drive motor (not shown) is operated by a predetermined signal during an image forming operation, a cam 14 as a vibration imparting means rotates and presses the scattering prevention member 13 intermittently. , FIG.
Move to the lower left inside. Each time it is pressed, the anti-scattering member 13 is pressed against the pressing force of the spring 15 as shown in FIG.
It receives drag on the upper right side inside. By repeating this operation, the scattering prevention member 13 vibrates substantially in the left-right direction in FIG. The frequency and amplitude of the vibration both increase to some extent, and the larger the value, the better the effect of preventing the scattering prevention member 13 from becoming dirty. However, when the value is too large, the vibration is not only transmitted to the scattering prevention member 13 but also to other members. It is not very desirable because it gives. Specifically, a frequency of 0.1 to 1
When the frequency is in the range of 00 Hz and the amplitude of 0.1 to 10 mm, a sufficient effect is obtained,
The amplitude may be in the range of 0.1 to 3 mm. In the present embodiment, the frequency is 1 Hz and the amplitude is 1 mm.

As described above, by applying a minute vibration to the scattering prevention member 13, a large amount of scattering toner is prevented from being accumulated in the scattering prevention member 13, and a stable and good image is always obtained. I got it.

<Embodiment 2> In the present embodiment, the frequency and amplitude of the vibration applied to the scattering prevention member 13 are changed according to the number of continuous image formations.
Is prevented from accumulating a large amount of scattered toner.

During continuous image formation, compared to the case where images are formed intermittently for each sheet, the time spent for ejection is shorter,
Accordingly, the amount of transfer residual toner accumulated in the magnetic brush charger 2 also increases. Therefore, the amount of toner scattered from the magnetic brush charger 2 increases during continuous image formation as compared with the case where one sheet is intermittent, and the vibration condition of the scattering prevention member 13 also needs to be changed accordingly.

Therefore, in this embodiment, as shown in FIG. 5, the frequency of the vibration applied to the scattering prevention member 13 is changed according to the number of continuous sheets. The larger the number of continuous paper passes, the greater the amount of scattered toner scattered from the magnetic brush charger 2. Therefore, in order to eliminate more toner adhering to the scatter prevention member 13, vibration increases as the number of continuous paper passes increases. The number is also increasing.

By making the frequency of the vibration applied to the scattering prevention member 13 variable according to FIG. 5, stable and good image formation could be performed even during continuous image formation.

In this embodiment, the frequency of the vibration applied to the scattering prevention member 13 is made variable in accordance with the number of continuous sheets passed. However, the amplitude of the vibration is made variable, or both the frequency and the amplitude are changed. Needless to say, similar effects can be obtained by making both of them variable.

<Embodiment 3> In the present embodiment, a large amount of scattered toner is accumulated in the scattering prevention member 13 by changing the frequency and amplitude of the vibration applied to the scattering prevention member 13 in accordance with the image ratio. It is to prevent that.

The transfer residual toner collected by the magnetic brush charger 2 naturally increases as the image ratio of the formed image increases. Accordingly, the amount of toner scattered from the magnetic brush charger 2 increases accordingly, and it is necessary to change the vibration condition of the scattering prevention member 13 accordingly.

Therefore, in the present embodiment, as shown in FIG. 6, the scattering prevention member 13 is provided in accordance with the image ratio of the image to be formed.
Was changed. The higher the image ratio of the image to be formed, the larger the amount of scattered toner scattered from the magnetic brush charger 2. Therefore, in order to remove more toner adhered to the scatter prevention member 13, the higher the image ratio, the higher the frequency. ing.

By making the frequency of the vibration applied to the scattering prevention member 13 variable according to FIG. 6, an image having a high image ratio could be formed satisfactorily.

In this embodiment, the frequency of the vibration applied to the scattering prevention member 13 is made variable in accordance with the image ratio.
It is a matter of course that the same effect can be obtained by making the amplitude of the vibration variable, or making both the frequency and the amplitude variable.

In the above embodiment, an example in which the toner image formed on the image carrier photosensitive drum 1 as an image carrier is directly transferred onto the recording material P has been described. The present invention is not limited to this. For example, a toner image formed on a photosensitive drum is temporarily transferred to an intermediate transfer member (an intermediate transfer belt or an intermediate transfer drum) as another member, and thereafter, the toner image is transferred from the intermediate transfer member. The present invention can also be applied to the case of transferring to a recording material.

[0067]

As described above, according to the present invention,
By preventing the scattered toner from being accumulated in the scattered toner shielding means, it is possible to effectively prevent an image defect caused by the scattered toner, for example, an image defect caused by the scattered toner adhering to the exposure device.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a longitudinal sectional view of a magnetic brush charger and scattered toner shielding means (scattering prevention member) according to the first embodiment.

FIG. 3 is a longitudinal sectional view of the developing device according to the first embodiment.

FIG. 4 is a longitudinal sectional view of a magnetic brush charger, scattered toner shielding means (scattering prevention member), and vibration applying means according to the first embodiment.

FIG. 5 is a diagram illustrating a relationship between the number of continuous paper passing and the frequency.

FIG. 6 is a diagram illustrating a relationship between an image ratio and a frequency.

FIG. 7 is a longitudinal sectional view showing a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Contact charging means (magnetic brush charger) 3 Latent image forming means (exposure means) 4 Developing means (developing apparatus) 5 Transfer means (transfer device) 13 Scattered toner shielding means (scattering prevention member) 14) Vibration applying means (cam) 15 Vibration applying means (spring) P Other members (recording material)

Claims (9)

[Claims] A contact charging unit configured to charge a surface of the image carrier; a latent image forming unit configured to form an electrostatic latent image on the charged surface of the image carrier; and a toner attached to the electrostatic latent image. An image forming apparatus comprising: developing means for developing as a toner image; and transfer means for transferring the toner image on the image carrier to another member, wherein the contact charging means along a moving direction of the surface of the image carrier. Scattered toner shielding means disposed on the downstream side to prevent scattered toner from the contact charging member from scattering to the downstream side, and a vibration imparting means for vibrating the scattered toner shielding means,
An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the vibration applying unit changes at least one of a vibration frequency and an amplitude of the vibration applied to the scattered toner shielding unit according to the number of continuous sheets of recording material on which an image is formed. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein the vibration applying unit changes at least one of a vibration frequency and an amplitude of the vibration applied to the scattered toner shielding unit in accordance with an image ratio of an image to be formed. The image forming apparatus according to claim 1. 4. The image according to claim 1, wherein the vibration applying unit applies a vibration having a frequency in a range of 0.1 to 100 Hz to the scattered toner shielding unit. Forming equipment. 5. The image forming apparatus according to claim 1, wherein the vibration applying unit applies vibration having an amplitude in a range of 0.1 to 10 mm to the scattered toner shielding unit. apparatus. 6. The image according to claim 1, wherein the vibration applying unit applies a vibration having a frequency of 0.1 to 10 Hz to the scattered toner shielding unit. Forming equipment. 7. The image forming apparatus according to claim 1, wherein the vibration applying unit applies vibration having an amplitude in a range of 0.1 to 3 mm to the scattered toner shielding unit. apparatus. 8. The apparatus according to claim 1, wherein said contact charging means is a magnetic brush charger having a magnetic brush on its surface which comes into contact with said image carrier. 7
An image forming apparatus according to claim 1. 9. The image forming apparatus according to claim 1, wherein said contact charging means has a conductive fiber on its surface, said conductive fiber being in contact with said image carrier.
An image forming apparatus according to claim 1.