JPS60166968A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a recording image having no color irregularity by making developers of three developing devices different in operation for charging by friction according to the easiness of the developers to charge. CONSTITUTION:The three developing devices 7, 7a, and 7b for three colors rotate agitators 12 and supply rollers 14 and 15 in their respective tanks to convey the developers from the tank bottom parts to upper developing rollers 17, thereby visualizing a latent image on a photosensitive body. A chain 21 is run by the operation of a motor 20 and electromagnetic clutches 31, 31a, and 31b are operated selectively to drive the developing rollers. At this time, the number of teeth of sprockets 22, 22a, and 22b or the external diameter of the respective developing rollers are varied mutually to make the feed speeds of the developers different according to the easiness of the toner to charge. Therefore, the charging amount of the toner is made uniform on the whole according to the extent of charging by friction using a doctor blade and a separator, thereby obtaining an image having no color irregularity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a developer that is carried while being carried on a developer carrier and is triboelectrically charged to make an electrostatic latent image formed on a latent image carrier visible. The present invention relates to a developing device in a multicolor recording device, which includes at least two developing devices for image formation.

Developing devices of the above type used in various multicolor recording devices such as multicolor electronic copying machines and multicolor printers are well known. In this type of device, a two-component developer consisting of toner and a carrier, or a one-component developer containing no carrier is used as the developer, and magnetic toner, non-magnetic toner, etc. are appropriately employed as the toner. An example of a developing device using a two-component developer is disclosed in detail in JP-A-55-55370.

This type of developing device sequentially forms visible images consisting of 1-toners of different colors on the latent image carrier using the developer contained in each developing device, thereby obtaining a multicolor recorded image. In this case, the visible image is obtained by electrostatically adhering toner triboelectrically charged to a predetermined polarity to an electrostatic latent image formed on a latent image carrier. However, this type of conventional developing device has the following drawbacks.

That is, there is a possibility that a difference in density occurs between the visible images of each color formed by each developing device, and that the quality of the completed recorded image, particularly the color tone reproducibility, deteriorates.

The reason for this is the 'JIS' electric charge (Q/
M; the amount of charge per unit weight) varies, so even if the surface potential of the electrostatic latent image on the latent image carrier is at the same level, the visible light formed by toner with an insufficient amount of charge may vary. This is because the density of the image is low, and the density of a visible image formed by toner with a sufficient amount of charge becomes high.

-1-An object of the present invention is to provide a developing device of the type mentioned at the outset, which makes it possible to eliminate or reduce the conventional drawbacks mentioned above.

(2) Below, the structure of the present invention will be explained based on illustrated embodiments.

Although the present invention can be applied to a developing device using any of the types of developer described above, the following examples will show a developing device using a two-component developer.

FIG. 1 is a schematic partial view showing an example of a multicolor electronic copying machine having a developing device according to the present invention.

A latent image carrier configured as a drum-shaped photoreceptor 1 is rotatably supported on the frame of a copying machine, and around it are a charger 2, a developing device! 3. Transfer drum 4, cleaning device w5,
A static eliminator 6 is provided respectively. The illustrated developing device 3 includes three developing devices, namely a yellow developing device 7 and a magenta developing device i7a.

and a cyan developing device 7b. Transfer drum 4
A transfer paper 8 is wrapped and clamped around the surface of the drum 4, and the drum 4 is driven to rotate clockwise. The circumferential speed of the transfer paper on the transfer drum and the circumferential speed of the photoreceptor 1 are set to be the same.

When a copying operation is started, the photoreceptor 1 is rotated counterclockwise, and the surface of the photoreceptor 1 is uniformly charged to a predetermined polarity by a charger 2. On the other hand, light reflected by an original (not shown) passes through a blue filter of an imaging optical system (not shown) and is irradiated onto the charged photoconductor portion. As a result, an electrostatic latent image is formed on the photoreceptor 2, which corresponds to an image mainly composed of yellow components of the original image, and when this latent image passes through the yellow developing device 7, the yellow toner forms a visible image ( yellow image). At this time, the other developing device 7a
, 7b, no developing operation is performed.

The above yellow image shows the transfer drum 4 rotating clockwise.
The yellow image on the photoreceptor 1 is transferred onto the transfer paper 8 by the action of a transfer device 9 fixedly provided on the back side of the transfer paper.

The toner remaining on the photoconductor 1 after transfer is removed by a cleaning device 5, and then the surface of this photoconductor is removed by a static eliminator 6.
, and is charged again by the charger 2 to proceed to the next image forming step.

In the next image forming process, after the light reflected by the same original as the one described above passes through a green filter (not shown),
The photoreceptor 1 is irradiated with light. As a result, an electrostatic latent image corresponding to an image mainly composed of magenta components of the original image is formed on the photoreceptor 1, and the latent image is converted into a visible image (magenta image) by the magenta developing device 7a.

On the other hand, the transfer paper 9 to which the yellow image has been transferred in the first image forming step is carried by the transfer drum 4, has its charge removed by the static eliminator 10, rotates once, contacts the photoconductor 1 again, and transfers the yellow image to the transfer paper 9. The magenta image on the photoreceptor is transferred from above by the action of the transfer device 9.

Similarly, in the next imaging step, it passed through a red filter (not shown). The reflected light from the original is irradiated onto the photoreceptor,
An electrostatic latent image corresponding to an image mainly composed of cyan components of the original image is formed on the photoreceptor 1, and this is converted into a visible image (cyan image) by the cyan developer 7b. This cyan image is also transferred onto the transfer paper 8 over the magenta image,
After the transfer paper 8 is neutralized by a static eliminator 10, it is transferred to the transfer drum 4.
The transferred image is then peeled off and subjected to a fixing process by a fixing device (not shown).

Next, details of the developing device 3 shown in FIG. 1 will be explained.

Each developing device 7, 7a, 7b has a developer 1.1, 11a, l.
Developing tanks 12゜12a, 12 each containing lb.
b, each tank 12, 1.2a.

Spiral agitators 13, 13a, 13b, which are rotated counterclockwise, are arranged at the lower part of 12b, and first supply rollers 14, 14a are provided on the right side thereof.

1'4b is provided. Furthermore, second supply rollers 15, 15a, and 15b are disposed above each of the first supply rollers, respectively. Also, second supply rollers 15, 15a,
Above the photoreceptor 15b, developer carriers configured as developing rollers 17.17a and 17b are provided, and each developing roller 17.17a and 1.7b is positioned facing the photoreceptor 1. . In this example, each of the above-mentioned supply roller and developing roller is made of a non-magnetic material, and each is driven to rotate in a counterclockwise direction. Also, inside these rollers,
Magnets 14', 14a', 14b', 15', 1
5a', 15b', 17', 17a',
17b' are fixed immovably.

Developer 11 contained in each developing tank 12, 12a, 12b. lla and llb are powdered two-component Vt imagers, each containing toner (coloring material and resin) colored in each color.
and a magnetic carrier.

These developers are conveyed upward from the bottom of the tank by the magnetic force of the magnet installed in each supply roller and the rotation of these rollers, and are transported upward from the bottom of the tank to each developing roller 17.17a,
17 b. Developing roller 17° 17a, 17b
The developer transferred to the developing rollers is also conveyed counterclockwise by the rotation of these rollers and the magnetic force of the magnets 17', 17a', and 17b' installed therein. Blade 1B, Lea, 18b
The amount of developer is regulated by The developer then reaches the area between the developer roller and the photoreceptor, where the toner in the developer electrostatically transfers to the electrostatic latent image on the photoreceptor 1, rendering the latent image visible. It will be done. It is clear from the above description that such a developing operation is not performed simultaneously in parallel in the three developing devices 7.7a, 7b, but is performed one by one one after another.

After the development, the developer is removed by the scrapers 19, 19a, 19.
b, scrapes off the developing rollers 17, 17a, +7b, and falls to the bottom of the developing tanks 12, 12a, 12b. Each tank 12, 12a, 12b is replenished with consumed toner by a toner replenishing device (not shown).

As mentioned above, the developer in the tank is sequentially conveyed on a plurality of rollers, and at that time, the doctor blades 18°+8a, 18
b and scrapers 19, 19a.

A mechanical external force is applied to the developer at the bottom of the tank by agitators 13 and 13a.

It is also stirred by 13b. For this reason, the toner and carrier come into frictional contact as if rubbing against each other, and are frictionally charged to opposite polarities. The toner is typically charged to the opposite polarity of the electrostatic latent image on the photoreceptor, allowing the 1-toner to electrostatically transfer to the electrostatic latent image and adhere to the photoreceptor by electrostatic forces.

The structure and operation described above are the same as those of conventional developing devices. In this case, in the conventional developing device, as described above, there is a possibility that a difference in density may occur in the visible images formed by the developer of each developing device.

This is due to variations in the amount of charge of the toner in each developing device.The reason for this variation can be explained below based on the configuration shown in Figure 1 using a two-component developer. It is as follows.

In other words, even if the surface potential on the photoreceptor is the same, the density of the visible image changes depending on the amount of charge (Q/M) of the toner that visualizes it. The amount of charge is related to the stirring action given to the developer,
If the stirring action is strengthened, the toner can be sufficiently charged; on the other hand, if the stirring action is insufficient, the amount of charge on the toner will be reduced.

On the other hand, the charge rise characteristics of toner are not necessarily constant, and usually differ depending on the type of toner (the charge rise characteristics of toner are the characteristics of toner when a certain frictional force is applied to the toner. (This is the time it takes for the amount of charge to reach a certain value; in other words, it is the ease with which the toner is charged.) In particular, in developing devices used in multicolor recording devices, the colors of toner contained in each developing device are different from each other, and therefore the coloring materials contained in each toner are different, so it is difficult to make the charging rise characteristics uniform. This is difficult, and therefore it is not uncommon for this characteristic to vary widely. Toner has different components depending on the manufacturer, so it is difficult to say with certainty which color toner is more likely to be charged or less likely to be charged.
Cyan toner may be the least likely to be charged, magenta toner may be most likely to be charged, and there may be others.

As mentioned above, although the charge rise characteristics may differ depending on the toner, in the past, stirring action was applied to the developer without paying particular consideration to this point.
Normally, the strength of the stirring action applied to the developer was approximately equal. For this reason, the amount of time it takes for the newly replenished toner to reach a sufficient charge level in the tank of each developing device varies depending on the developing device. There was a risk that differences would occur in the densities of the respective visible images formed due to these differences. Although it is possible to make the properties of the carrier used in each developing device different to prevent variations in the amount of charge of the toner, this is the case.

There is also a risk of putting the wrong carrier into the tank when replacing the developer, making the work complicated.

Therefore, in the developing device according to the present invention shown in FIG. 1, each developer 11. The structure is such that the strength of the stirring action applied to Ila and Il'b can be varied so that the amount of charge of each toner can be made uniform to the same and sufficient amount.

In the embodiment shown in FIG. 1, each developing roller 17° 17a
, 17b is varied depending on the ease with which each toner is charged, and the feeding speed of the developer that is difficult to charge is set higher than that of the developer that is easily charged. It is set to high speed.

If the feeding speed of the developer on the developing roller is increased, the external force applied to the developer by the developing roller is strengthened, and the external force received from the doctor blade and separator is also strengthened, which increases the agitation effect of the developer and increases the toner's agitation effect. It is possible to charge up to a predetermined amount of charge in a short time,
Therefore, by setting the feeding speed of each developer as described above, the amount of charge of the toner in each developer can be made uniform throughout, and color unevenness in the completed copied image can be suppressed.An example is given first. When a toner of Hfft having a charging rise characteristic shown as
) cyan developer, (2) yellow developer, (3) magenta developer.

As mentioned above, various specific configurations for varying the developer feeding speed are possible, and specific examples thereof are listed below.

FIG. 2 is an explanatory diagram showing an example of a drive system for driving the rollers and agitators of each developing device shown in FIG. 1.

In FIG. 2, the sprocket wheel 30 is rotated by the operation of the motor 20, and the chain 21 wound around the sprocket wheel 30 runs in the direction of the arrow. This driving force is transmitted to the yellow developing unit 7 via a sprocket wheel 22 and a gear 23.
It is transmitted to the developing roller 17 of the sprocket wheel 24, the gear 25, and the other sprocket wheel 26.
゜27.28, and these wheels 26, 27゜28
It is transmitted to the first supply roller 14, the second supply roller 15, and the agitator 13 via a chain 29 wound around, and these are driven in a predetermined direction. Each roller in the magenta developing device 7a and the cyan developing device 7b is also driven in the same manner as in the case of the yellow developing device 7. Each element in the magenta and cyan developing units 7a and 7b corresponding to each transmission element in the yellow developing unit 7 has a symbol a for each element in the yellow developing unit.

A code with b added is attached. Further, the sprocket wheels 24, 24a, 24b for each developing device are connected to the gears 25, 25a via electromagnetic clutches 31, 31a, 31b.
, 25b, and by selectively operating these electromagnetic clutches, the supply rollers and agitators of each developing unit 7, 7a, 7b are selectively operated, and each developing unit sequentially develops as described above. It is now possible to perform actions. Pulleys may be used instead of sprocket wheels, and belts may be used instead of chains.

In the configuration shown in FIG. 2, the developing roller 17° 17a
, 17b, for example, sprockets 22.7a, 7b for each developer.
What is necessary is to change the number of teeth of 22a and 22b so that their rotational speeds are different. As a result, even if the outer diameters of the developing rollers 17, 17a, and 17b are the same, their circumferential speeds are different from each other, and the developer on the developing roller with a fast circumferential speed is different from the developer on the roller with a slow circumferential speed. transported at a higher speed.

Alternatively, by changing the outer diameters of the developing rollers 17, 17a, 17b, even if the rotational speeds of the rollers 17, 17a, 17b are all the same, their circumferential speeds can be made to differ from each other. The same result can be obtained if the values are different. Of course, both the rotation speed and the outer diameter may be made different.

In addition, when each developing device has at least one member other than the developing roller (a supply roller and an agitator in the example shown in the figure) as a member that applies an agitating action to the developer and charges the toner, each developing device By making the operating speeds of these members different from each other, it is possible to change the strength of the stirring action applied to the developer in each developing device, and it is possible to obtain the same effect as in the configuration example shown above. In the configuration shown in Figure 2, the sprocket wheel 24°24
By making the numbers of teeth a and 24b different from each other, it is possible to make the operating speeds, that is, the rotational speeds of the supply roller and agitator of each developing device different from each other.

Note that even when each element of each developing device 7.7a, 7b is driven separately by an independent motor, the operating speed of each roller or agitator can be made different according to the above-mentioned idea.

In the embodiment shown in FIG. 1, the developing roller 17,
Magnets 17' installed inside 17a and 17b.

Although the magnets 17a', 17b' are fixed immovably, it is also possible, as is known per se, to drive these magnets in rotation, in which case each magnet 17', 17a'.

By changing the rotational speed of the rollers 17b', the speed at which the developer is fed on the developing rollers 17, 17a, and 17b can be changed, and the same effect as described above can be obtained. This configuration may be employed in combination with the configurations shown above.

By the way, like the developing device shown in FIG.

In a developing device that uses at least two developing devices along the moving direction of the latent image carrier (photoreceptor in the example shown), the developing device located downstream is A small amount of toner from the side developer is mixed in,
There was also the problem that the color purity of the developer in the downstream developing device was disturbed. To explain this in accordance with the configuration shown in FIG. 1, the developer present on the developing roller 17 of the yellow developing device 7 is
When a small amount of toner is scattered, this scattered toner moves in the rotational direction of the photoreceptor due to external force received from the rotating photoreceptor, and this scatters into the developing tank 12 of the magenta developer 7a.
The developer 1.1a in the tank 12a may get mixed in there and disturb the color of the developer 1.1a in the tank 12a. Similarly, the developer in the magenta developer 7a may mix into the cyan developer 7b.

Therefore, when implementing the above-described configuration in which the feeding speeds of the developer on each developing roller 17, 17a, and 17b are made different from each other, the rotational direction of the photoreceptor 1 is In view of this, it is advantageous to feed the developer on the downstream developing roller faster than on the upstream developing roller. For example, each developing roller 17
, 17a.

The circumferential speeds of 17b are Vl, V2. When set to V3,
By setting these to Vl<V2<V3, the above-described configuration can be realized. As a result, the developer on the developing roller 17 of the first developing device 7 is transported relatively slowly, so that less developer is scattered from the roller 17.
The inconvenience of the developer inside moving to the second developing device 7a can be reduced.

Similarly, less developer is transferred from the second developing device 7a to the third developing device 7b. When such a configuration is adopted, the toner that is least likely to be charged is used in the third developing device 7b, and the toner that is then charged and hazy is used in the second developing device 7a.
The toner that is most easily charged is transferred to the first developing device 7.
The object of the present invention can also be achieved if used in However, regardless of the ease with which toner is charged, it is also possible to employ the above-described configuration exclusively for the purpose of suppressing the developer of one developing device from being mixed with other developers.

In the above-mentioned embodiment, the peripheral speed of the developing roller in each developing device is made different, so that the strength of the effect applied to the developer for frictional charging is different in each developing device. The same strength of action may be applied to toners whose charge rise characteristics are similar to each other. For example, when yellow 1 to toner and magenta toner have similar charge rise characteristics, the circumferential speeds of the developing rollers in yellow developer 7 and magenta developer 7a are made the same, so that these developers 11°11a
When the same strength of agitation action is applied to the cyan toner and the charging rise characteristics of the cyan toner are different from other toners, the developer 11b of the cyan developer 7b is different from the other developer 1.
1; Provide a stirring action different from that of lla.

Further, although the illustrated embodiment shows a developing device having three developing devices, the present invention can also be applied to a developing device having more than two or three developing devices, and in this case as well, at least two developing devices can be used. The strength of the triboelectric charging effect applied to the developer in each developing device may be varied.

For a developer device having at least two developing devices that use a one-component developer made of magnetic or non-magnetic toner and triboelectrically charge the toner, 1 to 1 are used to triboelectrically charge the toner. By adjusting the applied pressure, the present invention can be applied without problems. Are you also good at recording devices other than electronic copying machines? The present invention is similarly applicable to a developing device that uses a member other than a developing roller, such as a belt, as a developer carrier.

■ The present invention allows the strength of the action to be applied to the developer in at least two developing devices for frictional charging to be different depending on the ease with which the developer in each developing device is charged. Since the developer is configured to have a stronger action than the easily charged developer, it is possible to obtain recorded images without color unevenness even when the charging rise characteristics of the toner in each developer differ.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a multicolor electronic copying machine having a developing device according to the present invention, and FIG. 2 is an explanatory perspective view schematically showing an example of a drive system of the developing device shown in FIG. 3...Developing device 7.7a, 7b...Developing device +1. lla, 1lb - developer

Claims (8)

[Claims] (1) At least two developing devices that visualize the electrostatic latent image formed on the latent image carrier using developer that is carried while being carried on the developer carrier and is frictionally charged. In the developing device of the multi-color recording device, the strength of the action applied to the developer in at least two developing devices for frictional charging is adjusted relative to each other depending on the ease with which the developer in each developing device is charged. The developing device is characterized in that a developer that is difficult to charge is given a stronger effect than a developer that is easily charged. (2) The developing device according to claim 1, wherein the feeding speed of the developer on at least two developer carriers is made different from each other. (3) Each of at least two developing devices is provided with at least one member other than the developer carrier that provides an action for triboelectrically charging the developer, and at least one member in each developing device is provided. The developing device according to claim 1 or 2, wherein the operating speeds of the developing devices are different from each other. (4) According to claim 2 or 3, at least two developer carriers are rotatably supported, and the circumferential speeds of the at least two developer carriers are made different from each other, so that the developer feeding speed is made different. developing device. (5) The developing device according to claim 4, wherein the rotational speed of at least two developer carriers is made different from each other, so that the developer feeding speed is made different. (6) According to claim 4 or 5, in which at least two developer carriers are configured as developing rollers, and the outer diameters of the rollers are made different from each other, so that the feeding speed of the developer is made different. developing device. (7) Claims 2 to 6 in which the feeding speed of the developer is varied by varying the number of rotations of the rotationally driven magnets installed in at least two developer carriers. Developing device according to any one of the items. (8) The developing device according to any one of claims 2 to 7, wherein a developing device with a high developer feeding speed is disposed on the downstream side when viewed in the moving direction of the latent image carrier. .