JPH0667525A - Image forming device - Google Patents

Abstract

PURPOSE:To bring a development unit, which is used for a drum-like image- forming device, into pressure-contact with the periphery of the drum in stable posture. CONSTITUTION:The development unit 14 is slidably held between the raised parts 51 of a frame 50. The guide part 14A of the development unit 14 on the drive side is supported by being engaged with the guide pin P of the front device substrate and the bottom on the same side is supported by the support part 53 of the frame 50. Also, the projection 14b of the opposite side is supported in the notch of the rear device substrate. In such a structure, striking roller 149 is brought into pressure-contact with the periphery of the photosensitive drum 10 by the energization of a compression spring S supported between the development unit 14 and the recess part 52 of the frame 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a plurality of developing devices, each containing a specified monochromatic developer, are arranged on the peripheral surface of a rotating drum-shaped photosensitive member.

[0002]

2. Description of the Related Art Many methods and apparatuses have been proposed for obtaining a color image by using an electrophotographic method. However, a large transfer drum is required in addition to the photoconductor, and the apparatus becomes large. In addition, there is a problem that the accuracy of superposition is required in order to transfer the toner image of a single color onto the transfer material every time it is formed.

Therefore, the applicant of the present invention repeatedly forms a latent image on the photoconductor in accordance with the number of separated colors of the original image and develops it with color toner to superimpose the color toner images on the photoconductor, and then uses this as a transfer material. Proposed a method of transferring to obtain a color image,
Already JP-A-60-75850, 60-76766, 60-95456
No. 60-95458, No. 60-158475, and the like.

According to this method, the transfer drum is unnecessary and the latent images on the photoconductors can be superposed with high accuracy, so that the above-mentioned problems are solved and a very practical color image forming apparatus is provided. It becomes possible to provide.

[0005]

As the color toners, there are usually used yellow (Y), magenta (M), cyan (C), and black (K) toners, and four toners containing the respective toners are used. Due to the fact that the developing device is placed on the surface of the photoconductor, when the photoconductor is a so-called photoconductor drum and a drum having a small outer diameter is used for compactness, the most downstream side in the rotation direction of the drum is used. The position of the developing unit containing the black toner installed in the position is unstable with respect to the surface of the photoconductor, and there is a possibility that the posture may change due to vibration or shock during power transmission.

In the extreme case, such a variation in the attitude of the developing device causes uneven development, resulting in deterioration of image quality. Particularly, a black developing device is frequently used and has a great influence on the image quality. It is similar.

The present invention solves this problem and improves the result.
An object of the present invention is to provide an image forming apparatus capable of developing a high quality image without being affected by vibrations or shocks by installing a developing device facing the surface of an image forming body in a stable posture with an extremely simple device. Is.

[0008]

The above object is to incorporate a rotating developing sleeve, carry a two-component developer on the developing sleeve, and develop a latent image on an image forming body to form a toner image. In the image forming apparatus including the developing device, the developing device is brought into pressure contact with the image forming body by the urging force of the elastic member, and the posture thereof is regulated by at least two supporting members supporting the driving side portion. It is achieved by an image forming apparatus characterized by being an apparatus.

[0009]

1 is a sectional view showing the construction of a color image forming apparatus as an embodiment of an image forming apparatus equipped with a developing device of the present invention.

First, the configuration and operation will be described.

In FIG. 1, reference numeral 10 denotes a photosensitive drum which is an image bearing member, which is formed by coating an OPC photosensitive member on the drum and is grounded and driven and rotated clockwise. Reference numeral 12 is a scorotron charger, and _VH (-600 to -800) is applied to the peripheral surface of the photosensitive drum 10.
V) uniform charging is provided by corona discharge with a grid and corona discharge wire whose potential is held at V _G (-550 to 850 V). Prior to the charging by the scorotron charger 12, the peripheral surface of the photoconductor is neutralized by exposure by the PCL 11 using a light emitting diode or the like in order to eliminate the history of the photoconductor until the previous printing.

After uniformly charging the photosensitive member, the image exposing means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 is a reflection mirror 1 through a polygon mirror 131 that rotates using a laser diode (not shown) as a light emitting source, an fθ lens, and the like.
The optical path is bent by 32 and scanning is performed, and a latent image is formed by the rotation (sub-scanning) of the photosensitive drum 10.
In this embodiment, the character portion is exposed to form a reverse latent image in which the character portion has a lower potential V _L (-100V to 0).

Yellow (Y) on the periphery of the photosensitive drum 10,
Developers each containing a developer composed of toner such as magenta (M), cyan (C), black (K), and a carrier.
14 is provided, and first, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer is a carrier in which a ferrite core is coated with an insulating resin around it, a polyester as a main material, a pigment according to the color, and a charge control agent,
It consists of toner to which silica, titanium oxide, etc. have been added.
The layer is regulated to a layer thickness (developer) of ˜600 μm and conveyed to the developing area.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.4 to larger than the layer thickness (developer).
With a thickness of 1.0 mm, an AC bay ice of V _AC (1.5 to 3.0 KV _PP ) and a DC bias of V _DC (-500 to -700 V) are superimposed and applied during this period. V _DC and V _H, for charging the toner are both the same polarity, the toner given the opportunity to leave from the carrier by V _AC is not adhere to a portion of the high V _H of potential than V _DC, V _DC The image is made visible (reverse development) by adhering to the V _L portion having a lower potential.

After the visualization of the first color is completed, the process proceeds to the image forming process of the second color, uniform charging is performed again by the scorotron charger 12, and a latent image based on the image data of the second color is formed by the image exposing means 13. To be done. At this time, the charge elimination by the PCL 11 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the rapid decrease in the potential around the image.

Once again, V is applied over the entire surface of the photosensitive drum 10.
A latent image similar to that of the first color is formed on the portion of the photoconductor having the _H potential and the image of the first color is not developed, but development is performed again on the portion having the image of the first color. In the portion to be performed, the latent image of V _M ′ is formed due to the light shielding by the toner of the first color and the electric charge of the toner itself, and V _DC
And development is performed according to the potential difference between V _M 'and V _M '. In the overlapping portion of the images of the first color and the second color, the development of the first color is V _L
Performed to create a latent image, since the balance between the first color and the second color is lost, reducing the exposure amount of the first color V _H> V _M (-
It may be an intermediate potential such that 100 to −300 V)> _VL .

An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the recording paper P fed from the paper feeding cassette 21 by the paper feeding mechanism 22 is fed to the transfer area by the transfer belt device 30 in which the transfer belt 31 is stretched, and the peripheral surface of the photosensitive drum 10 is fed. The above multicolor image is collectively transferred onto the recording paper P.

The transfer belt 31 has a thickness of 0.4 having a resistance of 10 ⁶ to 10 ¹⁴ Ω · cm formed by forming an outer FLC layer of a urethane rubber base.
An endless rubber belt of ~ 1.0mm, ribs may be provided at the ends to prevent deviation during rotation.

A film such as PET or a high resistance belt such as a film coated with these may be used if a charge removing mechanism is provided.

A holding roller 3 that stretches the transfer belt 31.
A voltage of V _PC is applied to the shaft 32a of the upstream side holding rollers 32 of Nos. 2 and 33, and at the position where the shaft 32a is installed via the transfer belt 31, as a means for imparting charge to the recording paper P. A conductive brush 34 is installed in a grounded state. The fed recording paper P enters between the brush 34 and the transfer belt 31, and the brush 34 injects an electric charge into the recording paper P, so that an attraction force is exerted between the recording paper P and the transfer belt 31. Occurs. After that, the recording paper P enters the nip portion (transfer area) 35 formed by the photoconductor drum 10 and the transfer belt 31, and the transfer electric field is generated from the back surface of the transfer belt 31 by the corona discharger 36 or the bias roller instead. A multicolor image is transferred onto the recording paper P.

The recording paper P separated from the photosensitive drum 10 is
The shaft 33a of the holding roller 33 on the downstream side which stretches the transfer belt 31.
Transfer belt 31 after receiving static electricity by AC corona discharge with the counter electrode as the counter electrode, or while receiving AC corona discharge.
Separate from. A cleaning blade 37 removes the toner attached to the rotating transfer belt 31. The transfer belt 31 of the transfer belt device 30 is separated from the photosensitive drum 10 about a shaft 33a of a holding roller 33 on the downstream side as a rotation center during the formation of a multicolor image.

The recording paper P holding the multicolor image separated from the transfer belt device 30 is conveyed to a fixing device 23 composed of two pressure-bonding rollers having a heater inside at least one roller, and is transferred between the pressure-bonding rollers. The applied toner is melted by applying heat and pressure, fixed on the recording paper P, and then discharged to the outside of the apparatus.

After the transfer, the residual toner remaining on the peripheral surface of the photosensitive drum 10 is subjected to static elimination by a static eliminator 15 using an AC corona discharger, and then the cleaning device 16 or the rubber material contacting the photosensitive body is removed. The cleaning blade 16a is scraped off into the cleaning device 16 and discharged or stored by a screw or the like. Depending on the arrangement of the static eliminator 15, the static eliminator 15 can also serve as static eliminator for the recording paper as shown in FIG.

The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 16 is exposed by the PCL 11 and then uniformly charged by the scorotron charger 12.
Enter the next image forming cycle. The cleaning blade 16a is separated from the surface of the photoconductor during the formation of the multicolor image,
AC neutralization by 15 is kept in OFF state.

FIG. 2 is a sectional view of the developing device 14, and FIG. 3 is a front view of the driving system.

Reference numeral 142 denotes a magnet roll contained in the developing sleeve 141, which has N and S magnetic poles arranged alternately or appropriately, and is fixed concentrically with the developing sleeve 141 and exerts a magnetic force on the peripheral surface of the non-magnetic sleeve. .

Reference numeral 143 denotes the layer forming rod described above, which is made of a magnetic or non-magnetic metal material, and is pressed uniformly against the peripheral surface of the developing sleeve 141 with a predetermined load in a non-rotating state by the urging of an elastic member. .

Reference numeral 144 denotes a scraper which is a developer peeling member for removing the developer on the peripheral surface of the developing sleeve 141, which is made of a hard urethane rubber material and has its tip end pressed against the peripheral surface of the sleeve by its elasticity.

Further, 145 is a supply roller for conveying the developer to the peripheral surface of the developing sleeve 141, which is made of a sponge material and conveys and supplies the developer by the frictional force of the peripheral surface.

Reference numerals 146 and 147 are a pair of stirring screws that rotate at the same speed in mutually opposite directions, and the toner replenished at the end of one stirring screw 147 is opposed by the rotation of the stirring screw 147. Partition wall being transported to the side end 1
It moves to the side of the stirring screw 146 through the end of 48, and in the process of being conveyed in opposite directions by the rotation of the stirring screw 146, it is agitated and mixed with the carrier held in the developing device 14 to evenly distribute the predetermined toner components. To be a two-component developer contained in.

Each of the above-mentioned stirring screws 146 and 147 is shown in FIG.
Gears G146 and G147 meshing with each other are fixed to the respective rotary shafts 146A and 147A as shown in FIG. 3, and are rotated in the directions of the arrows by the drive gear G0 of the power system of the apparatus main body.

On the other hand, in the developing sleeve 141 and the supply roller 145, as shown in the plan view of FIG. 4, the pulleys P141 and P145 are fixed on the respective rotating shafts protruding to the rear surface, and the rotating shaft of the stirring screw 147 is fixed. Pulley P14 on 147A
By the drive of 7, it is rotated in the direction of the arrow via the timing belt T.

The developer in which the toner and the carrier are evenly mixed by the rotation of the developing screws 146 and 147 is conveyed by the rotation of the supply roller 145 and is adsorbed and held on the peripheral surface of the developing sleeve 141.

The retained developer is the layer forming rod 143 described above.
The toner is transferred to the developing area of the photoconductor drum 10 by pressure contact with the toner, and the latent image is developed and visualized by transferring the toner to the peripheral surface of the drum by the above-mentioned potential difference.

Each of the developing devices 14 is mounted on a mount 50 as shown in FIGS. 3 and 4, and is installed on the peripheral surface of the photosensitive drum 10.

The pedestal 50 has a concave portion on a vertical surface in a state where the developing device 14 is slidably held by a rising portion 51 on the bottom surface.
By a bias of a pair of compression coil springs S sandwiched between the developing sleeve 141 and 52, a pair of abutting rollers 149 provided on the same axis of the developing sleeve 141 are pressed against the peripheral surface of the photosensitive drum 10, thereby developing sleeve 141. Are positioned with respect to the image area W on the peripheral surface of the drum with a predetermined developing interval suitable for non-contact developing.

Further, the pedestal 50 is provided with a supporting portion 53 on the bottom surface thereof, and the developing device 14 is provided with a horizontally elongated slot-shaped guide portion 14A on the side wall of the front surface thereof to be mounted on the pedestal 50. The developed developing device 14 has a bottom surface supported by the support portion 53 and the guide portion 14A on the side driven by the drive gear G0, that is, the side end portion on the front side in FIG. It is supported by the engagement of the protruding guide pins P of the base plate B1.

On the other hand, the opposite side of the developing device 14, that is, the side end on the back side in FIG. 3, is a protrusion on the side wall on the back side as shown in FIG.
By engaging 14B with the cutout portion of the device substrate B2, the entire developing device 14 is supported in an equilibrium state.

Therefore, the developing device 14 is firmly held by the support portion 53 and the guide pin P even if a slight vibration or shock is applied when the power transmission from the drive gear G0 is started. , The initial correct installation state is always maintained without any change in the posture with respect to the drum surface.

The pedestal 50 can be provided in each of the developing devices 14 and expected to have a corresponding effect. However, at least the lowermost black toner, which is the least stable with respect to the drum surface, is used. By using it for the developing device 14 accommodated therein, the effect can be further enhanced.

[0042]

According to the present invention, a plurality of developing devices arranged on the peripheral surface of the photosensitive drum are maintained in a pressed state with respect to the drum surface at all times, and as a result, the density caused by vibration or shock is increased. An image forming apparatus capable of obtaining a high quality image without unevenness is provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional configuration diagram of a developing device included in the apparatus.

FIG. 3 is a front view of the developing device.

FIG. 4 is a plan view of the developing device.

[Explanation of symbols]

 10 Photoreceptor Drum 11 PCL 12 Charger 13 Image Exposure Means 14 Developer 14A Guide 14B Protrusion 15 Static eliminator 16 Cleaning Device 21 Paper Feed Cassette 22 Paper Feed Mechanism 23 Fixing Device 31 Transfer Belt 36 Corona Discharger 50 Stand 51 Rise 52 recessed portion 53 support portion 141 developing sleeve 145 supply roller 146, 147 stirring screw G0, G146, G147 gear P141, P145, P147 pulley S compression coil spring T timing belt

Claims (1)

[Claims] 1. An image forming apparatus comprising a developing sleeve which rotates, wherein the developing sleeve carries a two-component developer to develop a latent image on an image forming body to form a toner image. In the apparatus, the developing device is a developing device that is brought into pressure contact with the image forming body by the biasing of an elastic member, and the biasing is restricted by at least two supporting members that support a side portion on the driving side. Image forming apparatus.