JPS60250369A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent mixing of different color toners and a reverse transfer of the toners, and to form a distinct toner image by providing each developing device so as to be displaceable with respect to an image forming body, approximating only a selected developing device, and executing development. CONSTITUTION:A titled device is constituted so that one end of a device frame of developing devices 5A-5C is supported by hinges 5A1-5C1, the other end side is received by eccentric cams 5A2-5C2, and the distance between the developing devices 5A-5C and an image forming body 1 can be changed by turning the cam. Also, when the developing device 5A is used, other devices are separated. Accordingly, it is prevented that a part of a toner image formed by the device 5A is scattered and mixed in other devices 5B, 5C, and on the contrary, a toner is transferred in reverse from the device which is not used. Therefore, no turbid color is generated, and a distinct toner image can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming device in a recording device such as an electrophotographic copying machine, and particularly to a latent image formed on an image forming body such as a color printer. The present invention relates to an image forming apparatus in which a toner image is developed by a arbitrarily selected part of a plurality of developing devices disposed near an image forming body.

[Prior art]

The image forming apparatus as described above is used as a recording apparatus that records color images. Color image recording apparatuses include those that superimpose toner images one color at a time on a transfer body such as recording paper, and those that superimpose toner images one color at a time on an image forming body. In the former method, a latent image of one color of color separation formed on an image forming body by an appropriate method such as electrophotography or electrostatic recording is transferred to one developing device having the corresponding color toner among a plurality of developing devices. A toner image is developed with a toner image and transferred to a transfer member, and then a latent image of another color formed on the image forming member is developed with another corresponding developing device and transferred to the same transfer member, and this process is repeated. Finally, a multicolor image is recorded by fixing the multicolor toner image on the transfer member. Since such an image forming apparatus transfers a toner image for each development, a means for rotating the transfer body is required.
As the size of the machine increases, the time required to form a multicolor image becomes longer, and there is a problem in that the overlapping toner images on the transfer member are more likely to be misaligned. On the other hand, in the latter type, an electrostatic latent image in the form of dots is formed by exposing the charged surface of the image forming body to one color of color separation using a laser beam scanner. One of the developing devices having the corresponding color toner is used for development, and the image forming surface is charged and exposed again for a different color without transferring the developed toner image, or An electrostatic latent image in the form of dots is formed by performing only image exposure using charging, and this electrostatic latent image is developed in the same manner as before with another developing device, and this process is repeated thereafter to form an electrostatic latent image on the image forming body. A multicolor image is formed by overlapping toner images one color at a time, and the multicolor image is transferred and fixed onto recording paper. here,
The development is preferably so-called reversal development in which toner is attached to the exposed area. In such a recording apparatus, the above-mentioned problems in the former recording apparatus are greatly alleviated. In addition to lasers, cathode ray tubes and LE
There are various types such as D, and there are also types in which an electrostatic latent image is directly formed on the dielectric surface of the image forming body using a multi-needle electrode or the like.

The above-mentioned recording devices can not only record multicolor images, but also
Of course, any monochromatic image can also be recorded. In the case where an image to be composited or each color image is formed by some of a plurality of developing devices, whether the toner images are superimposed on the transfer body or on the image forming body is determined. Even in the recording apparatus in which this is done, there is a problem in that toner from a toner image developed by one developing device is reversely transferred and mixed into another developing device, and as a result, the sharpness of the color of the image is gradually lost. However, problems still occur, such as toner being transferred from a developing device not used for development onto the surface of the image forming body, resulting in blurred colors. These problems are significant when toner images are superimposed on an image forming member or when developing is carried out by a method in which a developer layer formed on a developer transport carrier of a developing device is brought into contact with the surface of the image forming member. As a countermeasure for the latter case,
So-called jumping, in which a bias voltage having an alternating current component is applied to the developer transport carrier to cause toner to fly from the developer layer and transfer to the image forming body under an oscillating electric field without bringing the developer layer into contact with the surface of the image forming body. A method of developing according to this method is disclosed, for example, in Japanese Patent Laid-Open No. 14452/1983. However, even when development is performed by the jumping method, the contamination of different color toners cannot be easily eliminated. Although it is a small problem, toner may fly onto the surface of the image forming body from an unused developing device, or due to the phase of the alternating current component of the bias voltage, toner may flow between the image forming body and the developing device. This is because an electric force in the direction of the image forming body and an electric force in the opposite direction act, and a reverse transfer of the toner occurs due to the influence of the latter electric force.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problem of mixing of different color toners, and there is no risk of mixing of different color toners. An object of the present invention is to provide an image forming apparatus that can perform development under conditions where a clear toner image can be obtained without causing fogging or image disturbance without fear of transfer to the body. ] The present invention provides a step of developing a latent image formed on an image forming body into a toner image in the vicinity of the image forming body (some developing devices arbitrarily selected from a plurality of developing devices arranged). The image forming apparatus is characterized in that the distance of the developer transport carrier in the selected developing device to the image forming body can be changed depending on whether each developing device performs development. This configuration achieves the above object.

〔Example〕

The present invention will be explained below using illustrated examples.

Fig. 1 is a schematic structural drawing showing an example of a color image recording device, Fig. 2 is a cross-sectional schematic drawing showing an example of a developing device, Fig. 3 is a timing chart for color image formation, and Figs. 4 and 5 are developing devices. FIG. 3 is a partial schematic diagram showing an example of a mechanism for changing the distance of the developing section of the apparatus to the image forming body.

FIG. 1 shows the recording apparatus described above as a typical one that superimposes toner images on an image forming body.

That is, a drum J1-shaped image forming body 1 having a photoconductor layer on its surface rotates in the direction of the arrow, and its surface is uniformly charged by a scorotron charger 2, and a laser light source,
Acousto-optic modulator.

Image exposure from a laser beam scanner 3 consisting of a rotating polygon mirror or the like is incident through an imaging lens 4 to form an electrostatic latent image consisting of a low-potential dot configuration, and the electrostatic latent image is transferred to, for example, a developing device 5A. is developed into a toner image by reversal development, and the toner image is transferred to other developing devices 5B, 5G, transfer device 62, separator 7. Static eliminator8. When it passes through the position of the cleaning device 9 etc. and reaches the position of the charger 2, it is charged again as necessary, and then the image exposure is applied to the position where the previous toner image is formed. A latent image is formed, the electrostatic latent image is then developed by the developing device 5B, and the formation of the electrostatic latent image and the development by the developing device 5C are repeated in the same way, resulting in superposition of three color toner images. A color image consisting of is formed on the image forming body 1. This color image is transferred by the transfer device 6 to the recording paper P fed by the paper feeder 10, and the transferred recording paper P is separated from the surface of the image forming body 1 by the separator 7. , the color image is fixed by the roller fixing device 11. On the other hand, the residual toner on the surface of the image forming body l onto which the color image has been transferred is made easier to remove by the static eliminator 8, and the residual toner is removed by the cleaning device 9, and the surface is ready for the next color image to be formed. return.

With the above steps, one color image recording is completed.

The developing devices 5A to 5G are constructed as shown in FIG. That is, the developer transport carrier 51 has a magnet body 52 inside.
, the developer transport carrier 51 rotates to the left or stands still,
The magnet body 52 rotates clockwise and remains stationary, and the developer reservoir 53 is moved by the magnetic force of the N and S magnetic poles arranged on the surface of the magnet body 520.
The developer adsorbed onto the surface of the developer transport carrier 51 is moved in the direction of the arrow by both rotations or one of the rotations, and the thickness on the developer transport carrier 51 is controlled by the layer thickness regulating blade 54. is regulated to form a developer layer, and the developer layer develops an electrostatic latent image in a developing section a where the surface of the developer transport carrier 51 faces the surface of the image forming body 1.

For this purpose, a two-component developer consisting of a mixture of toner particles and carrier particles is preferably used as the developer, and a jumping method in which the toner particles are caused to fly from the developer layer for development is preferably employed.

In the jumping method, in particular, during development, a bias voltage having an AC component and a DC component is applied to the developer transport carrier 51 by the bias power supply 12.
An oscillating electric field is generated in the developing section a. The alternating current component of the bias voltage also gives vibration to the toner and developer layer, making it easier for the toner to transfer to the image forming body 1. This is a device that suppresses the occurrence of blemishes.

Therefore, by appropriately setting the alternating current component and the direct current component, a clear toner image can be developed. In addition, 13 is a protective resistor, 55 is a cleaning blade that removes the developer layer that has passed through the developing section a from the developer transport carrier 51 and returns it to the developer reservoir 53, and 58 is a stirring blade for the developer in the developer reservoir 53. stirring blades that uniformly mix the toner and carrier and triboelectrically charge the toner;
57 transfers the toner from the toner hopper 58 to the developer reservoir 53
This is a toner replenishment roller that replenishes toner.

FIG. 3 shows an example of charging, image exposure, and operation timing of each developing device 55 to 5C for forming a clear color image.

FIG. 3 shows the time from the start of charging by the scorotron charger 2 in terms of the rotation angle of the image forming body. In Fig. 3, a bias voltage consisting only of a DC component, similar to the DC component of the bias voltage during development, is applied to the developing device that does not participate in development to prevent color turbidity due to reverse transfer of toner. This is to prevent toner scattering, and the reason why the bias voltage at the time of development is such that the DC component has opposite polarity for a short time at the beginning and end is to minimize toner scattering. Such a bias voltage may be adjusted accordingly, for example, when image exposure is performed by negative image exposure and development is performed by attaching toner charged to the opposite polarity to that of the image forming member 1 to non-exposed areas. Of course, it can be changed. Further, depending on conditions, bias application during non-development can be omitted.

Although it is possible to form a clear color image in which toner images are superimposed on the image forming body 1 as described above, for example, toner may still be mixed into the developing devices 5B and 50 from the toner image formed by the developing device 5A. Color turbidity may occur due to toner being attached to the image forming member 1 from a developing device that does not participate in the development. outside,
The L1 developing devices 58 to 50 of the present invention are arranged so that the distance of the developing section to the image forming body 1 can be changed by the method shown in FIGS. The developing section is brought close to the image forming body 1, and the developing section of the developing device that does not perform development is kept away from the image forming body 1.

FIG. 4 shows that one end of the device frame of the developing devices 58-5C is supported by hinges 5A1-501, and the other end is supported by eccentric cams 512-51.
02, the distance between the developer transport carrier 51 and the image forming body 1 is changed by rotating the eccentric cams 5A2 to 5Ct2 to rotationally displace the developing devices 58 to 5G. Further, FIG. 5 shows developing devices 5A to 5.
C moves the rack and pinion 5 on the guide rails 5A3 to 5C3.
An example is shown in which the distance between the developer transport carrier 51 and the image forming body 1 is changed by being displaced by engagement with A4 to A4 to A4. Note that 14 is a pinion drive wheel.

With such a displacement mechanism, the developer transport carrier 5 of only the developing device that performs development is brought close to the image forming member 1, and toner transfer between the other developing devices and the image forming member 1 is performed. The image is formed at a distance that is likely to be far away from the object. Such an image forming apparatus not only reliably eliminates the problem of color turbidity due to toner reverse transfer and adhesion of toner from a developing device that does not participate in development, but also allows development to be performed independently of other developing devices. The developing conditions such as the bias voltage of the relevant developing device can be set to optimal conditions. Therefore, it is possible to form stable and clear multicolor images or monochrome images forever.

The distance between the developer transport carrier 51 and the image forming body 1 is preferably made variable by displacing the entire developing device as shown in FIGS. 4 and 5, but the relationship between the developer transport carrier 51 You can also use something that displaces just that part.

Further, the present invention will be explained by specific examples.

Example 1 An apparatus as shown in FIGS. 1, 2, and 4 was used.

The image forming body 1 has a selenium photoreceptor layer on its surface and has a diameter of 12 mm.
The zero scorotron charger 2, which rotates in the direction of the arrow at a surface speed of 200/sec, charges the surface of the image forming member 1 to 600 V each time an electrostatic latent image is formed. The laser beam scanner 3 uses a He-Ne laser as a light source,
Positive image exposure is performed each time to form an electrostatic latent image in the form of 50V dots on the charging surface of the image forming member 1. Developing device 58-5C
In this case, a two-component developer consisting of a mixture of a magnetic carrier and a non-magnetic toner is used as the developer in the developer reservoir 53. The magnetic carrier is a resin-coated spherical carrier with an average particle size of 30 μm, magnetization of 50 emu/y, and resistivity of 10” nm or more.The resistivity is determined by placing the particles in a container with a cross-sectional area of 0.5 ctn2. After tapping to a thickness of about 1 m, apply a load of 11 h/cm2 on the packed particles and calculate the current value when applying a voltage that generates an electric field of 100017 cm between the load and the bottom electrode. The toner is composed of 90 wt% thermoplastic resin, 10 wt% pigment, and a small amount of charge control agent, and has an average particle size of 10 μm. The pigment used is a magenta pigment in the developing device 5B, and a cyan pigment in the developing device 5C.The mixing ratio of carrier and toner in the developing devices 58 to 5C is 80:20 in ff1fit ratio. , the toner is charged to approximately +15 μC/y in the developer reservoir 53. After development,
The developer transport carrier 51 rotates counterclockwise at a surface speed of 200 ys/sec, and the magnet body 52 rotates clockwise at 1000 rpm.
The layer thickness of the developer layer formed on the developer transport carrier 51 was regulated to approximately 0.3+8 by a layer thickness regulating blade 54. In the developing devices 55 to 5G, the gap d between the developing section a and the image forming body 1 is set to 0.8 mm for those that perform development, and the gap d between the developing section a and the other developing devices is set to be 0.8 mm. . Incidentally, in order to easily displace the developing devices 5A to 5C, rotation of the developer transport carrier 51 and the magnet body 52 is performed by a single motor for each of the developing devices 58 to 5C. Moreover, this eliminates the need for external drive force transmission means and disconnection means such as clutches. Still developing devices 5A to 5C
The eccentric cups 5A2 to 502 that displace the shafts are also driven by individual motors. A bias voltage having a DC component of 500 cm and an AC component with a frequency of 2 kl (z, effective value 2 kV) is applied by the bias power supply 12 to the developer transport carrier 51 of the developing device that performs development. Do not apply bias voltage to developing devices that are

A large number of sheets of recording paper were obtained by forming three-color images under the above conditions, and clear front-color images without color mixture could always be recorded stably.

However, as in the example shown in FIG. 3, if a bias voltage consisting only of a DC component is applied to the developing device that does not perform development when the toner image or electrostatic latent image passes through the developing section a, Furthermore, even when the DC component of the bias voltage during development was set at about -300 V for a short time at the beginning and end, stable and clear color images could be recorded in the same way as described above.

〔Effect of the invention〕

According to the present invention, the developing device that performs development sets the distance of the developing section to the image forming body to be appropriate for development, and the developing device that does not perform development sets the distance of the developing section to the developing device where the toner is reversely transferred. A developing device that performs development rather than peeling off, which prevents the mixing of different color toners into the developing device and color turbidity in toner images because it can be separated from the device at a distance that does not cause the toner to transfer to the image forming body. It has the excellent effect of being able to set the developing conditions to the optimum conditions regardless of other developing devices, and therefore always forming and recording clear multicolor or monochrome images with stability. can get.

It should be noted that the present invention is not limited to the above-mentioned embodiment and can be applied to any recording apparatus having a plurality of developing devices. Therefore, it can be applied to, for example, a color copying machine that forms a latent image by color-separating the reflected or transmitted light of an original (-1) and irradiating it onto a photoreceptor, and various color printers that use an electrostatic recording method. When forming a multicolor image, the present invention is effective not only in an apparatus for superimposing toner images on an image forming body as in the embodiment, but also for an apparatus for superimposing images on a transfer body.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an example of a color image recording device, Fig. 2 is a cross-sectional schematic diagram showing an example of a developing device, Fig. 3 is a timing chart for color image formation, and Figs. 4 and 5 are development diagrams. FIG. 3 is a partial schematic diagram showing an example of a mechanism for changing the distance of the developing section of the apparatus to the image forming body. 1... Image forming body, 2-bath corotron charger) 3...
・Laser beam scanner, 4...imaging lens, 58-5C...developing device, 6.
...Transfer device, 7.Separator, 8.Static eliminator, 9.Cleaning device, 10.
...Paper feeding device, 11...Roller fixing device, P...
Recording paper, 51... Developer transport carrier, 52... Magnet, 53... Developer reservoir, 54... Layer thickness regulating blade, 12... Via child power supply, 13... Maintenance Setting resistance, 55・
... cleaning blade, 56 ... stirring blade, 57 ... toner supply roller, 5
8... Toner holder 1511-501... Hinge, 5A2-502... Eccentric cam, 5A3-503...
・Guide rail, 5A4-504...Pinion, 14...Pinion drive wheel. Figure 1 Figure a

Claims (4)

[Claims] (1) Image formation in which a step is performed in which a latent image formed on an image forming body is developed into a toner image by some developing device arbitrarily selected from among a plurality of developing devices arranged near the image forming body. An image forming apparatus characterized in that the distance between the developer transport carrier and the image forming body in the selected developing device can be changed depending on whether each developing device performs development. (2) The image forming apparatus according to claim 1, wherein the distance between the developer transport carrier and the image forming body is changed by displacing each developing device. (3) The image forming apparatus according to claim 2, wherein each developing device is rotationally displaced. (4) The developing device according to claim 2, wherein each developing device is linearly displaced.