JPS6337363A - image forming device - Google Patents

Abstract

PURPOSE:To stably obtain a good copy image by adjusting the driving of a developing bias voltage feeding means so that a potential difference between a developing bias voltage which is fed to the other developing device and a voltage in a non-scanning part becomes larger than a potential difference between a developing bias voltage which is fed to one developing device and a voltage in the non-scanning part. CONSTITUTION:An image carrying body, namely, a photosensitive drum 1 is supported axially by a shaft means so as to be freely rotatable in the direction as indicated with an arrow (a), and two pieces of developing devices consisting of a developing device 2 and a developing device 3 are provided in the vicinity of the outside edge part of the hotosensitive drum concerned 1. In this state, an inversion bias which has been set so that a substantial potential difference between a DC portion voltage of a developing bias voltage applied to a developing sleeve 16 from a developing bias power source 18, and a bright part potential on the photosensitive drum 1 becomes larger than a substantial potential difference between a DC portion voltage of a developing bias voltage applied to a developing sleeve 9 from a developing bias power source 12, and a bright part potential on the hotosensitive drum 1 is applied to the developing sleeve 16 from the developing bias power source 18, by which a magnetic particle 8 is made to adhere efficiently to a non-image forming area of the photosensitive drum 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to an image forming apparatus, and particularly relates to an image forming apparatus used as a color electrophotographic copying apparatus for two or more colors, for example.

1--11 Image forming apparatuses, especially electrophotographic copying apparatuses that use electrophotography to reproduce document image information, have conventionally implemented various techniques to ensure that good and stable copied images can be obtained from the apparatus. For example, two or more developing devices are provided near the outer edge of an image carrier such as a photoreceptor drum, and each of these two or more developing devices contains a different type of developer. (For example, in an electrophotographic copying machine that contains a black developer and a cyan developer.)

The developer housed in each of the developing units when the developing unit is in a developing process of visualizing the electrostatic latent image on the photoreceptor drum contains a different type of developer. One such measure is to prevent it from getting mixed into the developing device. It may be possible to completely prevent developer contamination during the development process by making the device configuration more complicated, but this may increase the cost of the entire device. This is impractical because maintenance becomes difficult, and when forming a multicolor image using multiple color developers, the developer installed upstream of the photoreceptor drum in the rotational direction has a brightness control. A developer located downstream of the developing device in the rotational direction of the photoreceptor drum contains a developer with a dark brightness, and a developer with a bright brightness stores a developer with a dark brightness. It is also possible to think of a method in which even if the compound is mixed into the agent, it does not pose a significant hindrance to good image formation. However, the countermeasures against the above-mentioned developer contamination are only good if the developers use the same development method, but for example: One uses a so-called two-component developer that uses a carrier such as magnetic particles to impart a charge to the toner, and the other uses a so-called one-component developer that does not use the above-mentioned carrier. If different developing methods are adopted for the two-component developers, this cannot be an effective countermeasure for the reasons described below. In other words, when the developing device containing the two-component developer is in the developing process. The two-component developer adhering to the surface of the photoreceptor drum, in particular, the one-component developer in which the carrier is disposed downstream in the rotational direction of the photoreceptor drum than the developing device through the surface of the photoreceptor drum. Unlike two-component developers, when a l-component developer gets mixed into a developing device containing a developer, it is essential to apply a thin layer onto the developing sleeve in the developer. If foreign substances such as carriers are mixed in during the thin layer coating described in +iii, uniform and stable coating of the one-component developer is essential; Become.

Therefore, a copy image is formed with the coating state of the l-component developer remaining non-uniform, so that the above-described image forming apparatus has the problem that only a poor copy image can be obtained. .

Therefore, the present invention was devised to solve the above-mentioned problems in conventional image forming apparatuses, and its purpose is to provide an image forming apparatus that can stably obtain good copy images. It is about providing.

+1 - This is achieved by the image forming apparatus according to the present invention. To summarize, the present invention includes an image carrier movable in one direction, and a two-component developer disposed near the image carrier to visualize a latent image formed on the image carrier. A developing device containing a developer, and a latent image formed on the image carrier, which is disposed near the image carrier on a downstream side of the developing device in the direction of movement of the image carrier, and visualizes a latent image formed on the image carrier. tti for
A developing bias is applied when converting the Hs image formed on the image carrier into a JIEI image in another developing device containing a separate developer and a developing device containing the two-component developer. a developing bias voltage feeding means for feeding a voltage;
another developing bias voltage supply means for supplying a developing bias voltage for visualizing the latent image formed on the image carrier to another developing device containing a component-based developer; and the two-component developer. A developing bias voltage supplied to a developing device containing a system developer and a non-image area on the image carrier when the developing device visualizes a latent image formed on the image carrier. When the other developing device containing the l-component developer converts the latent image formed on the image carrier into an 1iIll image, the power is supplied to the other developing device. and a potential difference adjusting means for adjusting the drive of each of the developing bias voltage supply means so that the potential difference between the developing bias voltage and the voltage at the non-image area of the image carrier becomes larger. Image forming device! ! .

Lm 1 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an imaging bag according to one embodiment of the present invention. The image forming apparatus according to one embodiment of the present invention will be explained by taking as an example an image forming apparatus using Carlson electrophotography, and since the overall structure thereof is already well known, the image forming apparatus according to the present invention is a photosensitive image carrier. The body drum and the developing device provided near the outer edge of the photosensitive drum are shown in detail, and illustrations of the primary charging means, exposure means, cleaning means, etc. in the Carlson process are omitted.

In FIG. 1, an image bearing member, that is, a photosensitive drum l is rotatably supported by a shaft means (not shown) i in the direction of an arrow a, and a developing device 2 is located near the outer edge of the photosensitive drum l. Two developing devices, ie, developing device 3 and developing device 3, are provided. For the photoreceptor on the photoreceptor drum l, a known photoreceptor such as OPC is used, and on the photoreceptor there is used a known photoreceptor (1'1 electric means, image exposure means, etc.). An electrostatic latent image is formed.The developer 2 is disposed upstream of the developer 3 in the rotational direction of the photoreceptor drum 1.The developer 2 is.

Place it above the developer unit 2 body! , 13; a replenishment member 6 facing the downward opening of the toner cartridge 4 and rotatably supported in the direction of the arrow (clockwise); An agitation member 7 disposed substantially directly below the supply member 6 at the bottom of the developing device 2 main body and rotatably supported in the direction of the arrow (counterclockwise), the developing device 2 main body and the photosensitive drum 1 are connected to each other. A developing sleeve 9 facing an opening opening on the facing gap side and rotatably supported; and a regulating blade 1 disposed in the opening together with the developing sleeve 9.
Consists of 1. The above-mentioned toner cartridge 4 contains, for example, blue non-magnetic toner 5, and by driving the replenishing member 6, the toner 5 is delivered to the developing device 2 as necessary.
It is designed to be supplied to the main body side. The stirring member 7 stirs the blue non-magnetic toner 5 provided from the toner cartridge 4 and the magnetic particles 8 housed in the main body of the developing device 2 by driving the replenishing member 6, thereby stirring the toner 5. The toner 5 is mixed with the magnetic particles 8 to seal the toner 5 with a predetermined charge by tripo-electrification. The developing sleeve 9 has magnetic poles N1.
31. A magnet roll 10 with N2.52 is fixed. The developing sleeve 9 rotates in the direction indicated by the arrow (counterclockwise), and cooperates with the magnetic force of the magnet roll 10 to collect magnetic particles to which toner 5 is attached, which is restrained by the magnetic pole S2 of the magnet roll 10. 8, that is, the two-component developer is carried out toward the outside of the developing device 2. The regulating blade 11 is configured to control the ? The conveyance rate of the component type developer is regulated to a predetermined amount. Development bias voltage supply means, development bias, t
The i source 12 applies a developing bias voltage on which an alternating current component is superimposed to the developing sleeve 9, thereby being restrained at a developing portion of the developing sleeve 9 facing the outer circumferential surface of the photoreceptor drum l. The two-component developer is supplied onto the photoreceptor drum l, and the photoreceptor drum 1-1=
It is configured to develop a latent image on the static image '1 formed on the surface.

As described above, the developing device 3 is used for the developing! 12 in the rotational direction of the photoreceptor drum l.

The developing device 3 includes a feeding member 14 disposed at the bottom of the developing device 3 body and rotatably supported in the direction of the arrow (counterclockwise), the developing device 3 body and the photosensitive drum l described in 1iii. A developing sleeve 16 is rotatably supported facing an opening opening on the opposing gap side, and a magnetic blade 17 is disposed in the opening together with the developing sleeve 16. Equipped with When driven, the feeding member 14 transfers the black one-component magnetic toner 13 housed in the main body of the developing device 3 to the developing sleeve 1.
It is to be transferred to the 6th side. The aforementioned developing sleeve 1
6 has magnetic poles N3, S3 . N4. A magnet roll 15 having S4 is fixed. The developing sleeve 16 rotates in the direction of arrow C (counterclockwise) and cooperates with the magnetic force of the magnet roll 15 to transfer the toner 13 restrained by the magnetic pole S4 of the magnet roll 15 to the outside of the developing device 3. It is now being transported to. The magnetic blade 17 is connected to the developing sleeve 16
A predetermined amount (i.e., a predetermined amount of the L-component magnetic toner 13 that has been transported toward the outside of the developing device 3 by the rotation of The formation of a thin layer of toner 13 on the development area facing the outer circumferential surface of the toner 13 is regulated to a usable amount. The developing bias voltage power supply means, that is, the developing bias power supply 18 applies a developing bias voltage on which an alternating current component is superimposed to the developing sleeve 16, thereby causing the developing sleeve 16 to face the outer circumferential surface of the photoreceptor drum 1. The toner 13, which is bound to the developing area and formed in a thin layer, is supplied onto the photosensitive drum l-.

It is configured to develop the electrostatic latent image formed on the photoreceptor drum l. 'WL position difference adjustment means, that is, based on sensor information outputted from various known detection means for potential difference control built in a control unit that controls the driving of the entire image forming apparatus, By controlling the driving of the primary charging means, exposure means, etc. disposed near the outer peripheral surface of the drum l, and controlling the driving of the aforementioned developing bias power supply 12.18, as will be described later, The potential difference between the potential of the non-image area, that is, the bright area, and the developing bias voltage applied to the developing sleeves 9 and 16 by the developing bias voltage @12°18 is controlled to be a constant value.

The magnetic particles 8 housed in the main body of the developing device 2 described above may be of any kind as long as they are commonly used as two-component developers; In the image forming apparatus according to one embodiment, the maximum magnetization is 6
0 e mu / g, average particle diameter of 30~tooIL, nearly spherical ferrite particles coated with silicone resin and having a relatively high resistance value are used. The toner 5 accommodated in the toner cartridge 4 of the developing device 2 includes a styrene/butadiene copolymer resin 1.
0.00 parts, colloidal silica 0.00 parts, toner powder with an average particle size of 10 IL consisting of 43 parts of copper phthalocyanine type powder and 0.00 parts of colloidal silica.
Blue toner with 6% added externally is used. On the other hand, the l-component magnetic toner 13 housed in the main body of the developing device 3 uses insulating particles having an average particle size of Pl-10JL and consisting of 100 parts of styrene-acrylic resin and 100 parts of magnetite.

In the image forming apparatus as described above, the photosensitive drum l
Potential MD of the image area, that is, the dark area of the electrostatic latent image formed above
I VD1=-600V, the static 'IttPP! Statue No. 1
The potential VL1 of the 51 part is set to VLl=-150V, the opposing gap between the outer circumferential surface of the photoreceptor drum l and the outer circumferential surface of the developing sleeve 9 is set to about 400 #L, and a potential control microcomputer (not shown) is set. ) The developing bias applied to the developing sleeve 9 from the developing bias power supply 12 is set to a frequency of 1.6 KH2 based on a drive command signal from the developing bias power source 12.
When a voltage with a voltage waveform having a peak-to-peak value of 1.4 KV and a center value of 1,300 V was applied, a good developed image without uneven development or fog could be obtained. However, when inspecting the surface of the photoreceptor drum 1 at this time, it is found that a small amount of magnetic particles 8 are attached to the non-image forming area on the surface of the photoreceptor drum 1, and the photoreceptor drum 1 that has passed through the area where the developing device 3 is installed. It became clear that the magnetic particles 8 were not attached to the surface of the developing sleeve 16, and most of them had been transferred onto the developing sleeve 16. By the way, if the magnetic particles 8 attached to the developing sleeve 16 are left as they are, the magnetic particles 8 will move in the order of the developing device 3 main body side → the magnetic blade 17 → the above-mentioned opposing gap due to the rotation of the developing sleeve 16. If there is a particularly large amount of attached magnetic particles 8, they will be trapped near the magnetic blade 17, clogging the narrow gap between the developing sleeve 16 and the magnetic blade 17, and forming a thin layer on the developing area. This causes streaks and unevenness to occur in the toner 13 being spread on the cloth.As a countermeasure to eliminate such problems, the above-mentioned method of changing the internal structure of the device itself, for example, the photoreceptor drum l. The magnetic particles 8 attached to the outer circumferential surface of the magnet roll 15 are extended to a range where the magnetic force of the magnet roll 15 does not reach (a distance of about 10 mm when using a general magnet roll used in a copying machine). The first thing to think about is a method of separating the developing unit 3 from the photoreceptor drum l, but in order to realize such a method, it is necessary to at least increase the size of the image forming apparatus to create a space for separating the developing unit 3 from the photoreceptor drum l. This requires a drive mechanism to separate the device 3 from the photoreceptor drum l.

Therefore, in view of this situation, the inventor of the present invention devised a method in which the magnetic particles 8 mixed into the developing device 3 during the developing process of the developing device 2 have a polarity opposite to that of the toner 13. The position of the magnetic particles in the container 2 on the triboelectrification series is selected so that when the magnetic particles 8 mix into the toner 13 in the developing device 3 and are rubbed, they will be charged to the opposite polarity to the toner 13. This makes it easier for the mixed magnetic particles 8 to adhere to the non-image forming area of the photosensitive drum 1 when the developing device 3 is in the developing process. Furthermore, the present inventor has discovered that the substantial potential difference between the DC component voltage of the developing bias voltage applied to the developing sleeve 16 from the developing bias power source 1B and the bright area potential of the photosensitive drum 11 is determined by the developing bias voltage fi12. The reversal bias is set to be larger than the actual potential between the DC component voltage of the developing bias voltage applied to the sleeve 9 and the potential of the Il1 portion on the photoreceptor drum L-.
It has been found that by applying a voltage to the developing sleeve 16 from the developing bias power source 18, the magnetic particles B can be efficiently attached to the non-image forming area of the photosensitive drum I.

- For example, in the developing process of the developing device 2, the bright area potential of the photoreceptor drum l is -150V, and the developing bias voltage is [1].
The DC voltage of the developing bias applied from 2 to the developing sleeve 9 is -300 V, and the potential difference between the two is 150 V.
By setting the potential of the first part of 1 to -50V, setting the voltage of the DC component of the developing bias applied from the developing bias voltage $18 to the developing sleeve 16 to -500 V, and setting the potential difference between the two to 450 V, the voltage inside the developing unit 3 is set to The mixed magnetic particles 8 of negative polarity do not accumulate in the developing device 3, which houses the positively charged toner 13, but go out of the developing device 3 and are once again deposited on the photosensitive drum l. The attached magnetic particles 8 adhere to the non-image forming area and are not transferred to the photosensitive drum 1 by a negative corona transfer charger (not shown).
-1-, and was removed from the photosensitive drum l by a cleaning means (not shown). Unreleased 1jl mentioned above
In one embodiment according to the development bias power supply 12.18
The application timing of the inversion bias applied to the developing sleeve 9.16 may be set to coincide with the process of developing the electrostatic latent image corresponding to the original image, but since the image density of the copied image becomes lighter, the timing of applying the reverse bias to the developing sleeve 9. Performing the process in which the latent image is not developed, for example, during the semi-11111M transfer period of the main body of the image forming apparatus, during the idle operation period to prevent memory in the photosensitive drum l, or in a process such as a non-image forming area between original images. is desirable.

As is clear from the content explained above, in one embodiment according to the present invention, the electrostatic W formed on the photoreceptor drum l
Although the process of developing IgIl alternately with the two developing devices 2 and 3 has been described, the present invention is not limited to the above content. It can also be applied to a case where a process is used in which a film is formed in advance and multiple development is performed using the two developing devices 2 and 3 described above. In addition, in accordance with the above-mentioned present invention - in the example 2
Although we have explained the case where the polarities of the developers contained in the two developing units 2 and 3 are the same, there is no problem even if they have different polarities, and the number of developing units is not limited to two, and more can be added. Of course, there is no problem.

As explained above, according to the present invention, when the developing device containing the 2r & split system developer visualizes the latent image formed on the image carrier, the latent image formed on the image carrier is The potential difference between the developing bias voltage supplied to the device and the voltage at the non-image area on the image carrier indicates that another developing device containing the l-component developer is formed on the image carrier. Each developing bias voltage is supplied so that the potential difference between the developing bias voltage supplied to the other developing device and the potential at the non-image area on the image carrier when converting the latent image into a IIIJ image is larger. Since the drive of the means is adjusted, it is possible to provide an image forming apparatus that can stably obtain good copy images.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing the main parts of an image forming apparatus according to an embodiment of the present invention. 1: Photosensitive drum 2: Developing device 3: Developing device 5: Non-magnetic toner 8: Magnetic particles 9: Developing sleeve 10: Magnet roll 12: Developing bias power supply 13: IN & separate magnetic toner 15: Magnet roll 16: Developing sleeve 18: Developing bias power supply copper 1 diagram

Claims (1)

[Scope of Claims] 1) An image carrier movable in one direction, and a two-component system disposed near the image carrier to visualize a latent image formed on the image carrier. A developing device containing a developer, and a latent image formed on the image supporting member, which is disposed near the image supporting member on the downstream side of the developing device in the moving direction of the image supporting member, is used to develop a latent image formed on the image supporting member. The latent image formed on the image carrier is visualized in another developing device containing a one-component developer and a developing device containing the two-component developer. A developing bias voltage power supply means for supplying a developing bias voltage at the time of developing, and another developing device containing the one-component developer at the time of visualizing the latent image formed on the image carrier. Another developing bias voltage power supply means for supplying a bias voltage, and a developing device containing the two-component developer when the developing device visualizes a latent image formed on the image carrier. The difference in potential between the supplied developing bias voltage and the voltage at the non-image area on the image carrier is
A developing bias voltage supplied to another developing device containing a component-based developer and a voltage applied to the image carrier when the other developing device visualizes a latent image formed on the image carrier. An image forming apparatus comprising: a potential difference adjusting means for adjusting the drive of each of the developing bias voltage power supply means so that the potential difference with respect to a voltage in a non-image area becomes larger. 2) The image forming apparatus according to claim 1, wherein the two-component developer and the one-component developer contained in each of the developing devices have different color tones. 3) The image forming apparatus according to claim 1, wherein the two-component developer and the one-component developer contained in each of the developing devices have the same color tone. 4) The developing bias applied from each of the developing bias voltage supply means to each developing device is an inverted bias, and the timing of application of the inverted bias is determined during development to develop the latent image formed on the image carrier. The image forming apparatus according to any one of claims 1 to 3, characterized in that the image forming apparatus is a step or a step in which the development is not performed.