JPH11161002A - Multicolor image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor image forming device capable of securing the stable operation of a developing cartridge switching mechanism by preventing the soiling with scattered toner of an optical detecting means for deciding the stopping positions of developing cartridges. SOLUTION: The device is provided with stopping position flags IM, IC, 1Y and 1K corresponding to the developing cartridges 100M, 100C, 100Y and 100K and the developing cartridge switching mechanism for rotationally moving the developing cartridges 100M, 100C, 100Y and 100K to a position facing an image carrier. Then, the stopping position flags 1M, 1C, 1Y and 1L are detected by the revolution position sensor (optical detecting means) 2 arranged in a device main body, so that the developing cartridges 100M, 100C, 100Y and 100K are successively selected/switched to form a multicolor image. In such a case, it is constituted so that the stopping position flags 1M, 1C, 1Y and 1K are constituted of surfaces having fixed angles with a flag locus circle 10 and when the developing cartridge switching mechanism is stopped, the flags are stopped in a position for covering the revolution position sensor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus such as a color copying machine or a color printer employing an electrophotographic system.

[0002]

2. Description of the Related Art Heretofore, a multi-color image forming apparatus has a multi-color image formed by removably mounting a developing cartridge having a developer of each color with respect to an image carrier, and superposing each color image. In the image forming apparatus, the developing cartridge is provided integrally with the developing switching mechanism. A stop position flag is provided on the holding side plate of the developing cartridge, and a stop position sensor corresponding to the stop position flag is provided on the apparatus main body, so as to perform selection switching of the developing cartridge and detection of the stop position.

[0003]

However, there is a problem that scattered toner generated at the time of development adheres to and penetrates the light emitting portion and the light receiving portion of the light transmission type sensor which determines the stop position of the developing cartridge. Since the scattered toner is generated when a high AC voltage is applied during development, the scattered toner is also referred to as an AC scattered toner. In an image forming apparatus using a non-magnetic one-component toner, the scattered toner is significantly generated.

If scattered toner adheres to the light transmitting sensor light emitting unit and the light receiving unit, the amount of light received by the light transmitting sensor becomes unstable, and the stop position of the developing cartridge becomes unstable, and the development switching is not performed. Problems such as loss of control of the mechanism have occurred.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to prevent the optical detection means for determining the stop position of a developing cartridge from being contaminated by scattered toner and to stably operate a developing cartridge switching mechanism. To provide a multi-color image forming apparatus capable of ensuring image quality.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of detachable developing cartridges are mounted, a flag corresponding to each of the developing cartridges is provided, and an image carrier is provided. A developing cartridge switching mechanism for rotating and moving the developing cartridge to an opposing position, wherein the developing cartridge is sequentially selected and switched by detecting the flag with an optical detecting means provided on the mounting body, and a plurality of developing processes are performed. A multi-color image forming apparatus that forms a multi-color image by forming a multi-color image through the multi-color image forming apparatus, the flag is formed on a surface having a certain angle with respect to a flag locus, and the developing cartridge switching mechanism is stopped. Sometimes, the flag is formed at a position that shields the image carrier and the optical detection means.

According to a second aspect of the present invention, in the first aspect of the invention, a plurality of rib-like projections are formed on the same plane on which the flag is formed in a substantially radial shape from the rotation center of the developing cartridge switching mechanism. It is characterized by the following.

Therefore, according to the first aspect of the present invention, since the flag is formed on the surface having a constant angle with respect to the flag locus, it becomes difficult for the scattered toner to approach the periphery of the optical detection means, and the optical detection means The scattered toner once adhered can be blown off. Further, when the developing cartridge switching mechanism is stopped, the flag is stopped at a position covering the optical detecting means, so that it is possible to prevent the scattering toner from adhering to the optical detecting means immediately after the stopping of the developing cartridge switching mechanism. A stable operation of the developing cartridge switching mechanism can be ensured.

According to the second aspect of the present invention, since a plurality of rib-like projections are formed on the same plane on which the flag is formed in a substantially radial shape from the rotation center of the developing cartridge switching mechanism, a strong wind around the optical detecting means is provided. Is generated, and the adhesion of the scattered toner to the optical detection means is more effectively prevented by the flow of the wind.

[0010]

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

First Embodiment "Overall Description of Multicolor Image Forming Apparatus" First, the overall configuration of a color image forming apparatus will be described with reference to FIG. FIG. 6 is a cross-sectional view of a laser beam printer which is one mode of the color image forming apparatus.

The laser beam printer shown in FIG. 6 winds a transfer material 22 fed from a paper feed unit 21 around a transfer drum 23, and rotates four transfer cartridges 100M, 100C, 100Y, and 100K around the transfer material 22. The toner image developed in the image forming unit provided with the image forming unit is transferred in a multiplex manner to form a color image. And this transfer material 22
Is transported to a fixing unit 26 to fix the color image on the transfer material 22, and the transfer material 22 on which the color image has been fixed is discharged to a discharge unit 28 in the upper part of the apparatus by a discharge roller pair 27. The four rotatable developing cartridges 100M, 100M
The developing means 100 including C, 100Y, and 100K is configured to be individually detachable from the apparatus main body 29.

Incidentally, the exposure to the image forming section is sent from a scanner section 30. That is, when an image signal is given to the laser diode, the laser diode irradiates the polygon mirror 30a with image light corresponding to the image signal. Then, the image light reflected by the polygon mirror 30a is radiated from the exposure unit of the image carrier unit via the imaging lens 30b and the reflection mirror 30c, so that the image carrier 24
is selectively exposed to form an electrostatic latent image on the image carrier 24a.

Next, the configuration of each section of the image forming section will be sequentially described in detail.

[Paper Feeding Unit] The paper feeding unit 21 feeds the transfer material 22 to the image forming unit, and a paper feed cassette 21 a containing a plurality of transfer materials 22 is provided at the inner bottom of the apparatus main body 29. It is loaded.

During image formation, the feed rollers 21
b is driven and rotated in accordance with the image forming operation, and the cassette 21 is rotated.
a, the transfer material 22 in a is separated and fed one by one,
The transfer material 22 is guided by the guide plate 21c, and is fed to the transfer drum 23 via the registration rollers 21e.

[Transfer Drum] The transfer drum 23 winds the fed transfer material 22 and rotates in the direction of the arrow in FIG. 6 to transfer each color toner to the transfer material 22.

The transfer drum 23 according to this embodiment is formed by forming an elastic layer 23b such as sponge or rubber on the outer periphery of an aluminum cylinder 23a having a diameter of about 160 mm. The transfer drum 23 is rotatably supported by a fixed shaft 23e, and transmits the driving force of a driving motor to a gear (not shown) fixed to the fixed shaft 23e, so that the direction of the arrow in FIG. It is configured to be.

A gripper 23f is provided at a predetermined position on the outer periphery of the transfer drum 23.
The two tips are maintained by the gripper 23f.

Further, on the outer periphery of the transfer drum 23, an electrostatic attraction roller 23g is provided so as to be able to contact and separate therefrom.
Is pressed between the electrostatic attraction roller 23g and the transfer drum 23 to press the outer periphery of the transfer drum 23, and
By applying a voltage between the transfer material 22 and the transfer drum 23, electric charges are induced in the dielectric transfer material 22 and the dielectric layer 23d of the transfer drum 23, and the transfer material 22 is settled on the outer periphery of the transfer drum 23. Electroadsorbs.

"Image Carrier Unit" The image carrier 24a according to the present embodiment is formed by applying an organic photoconductor layer to the outer peripheral surface of an aluminum cylinder having a diameter of about 40 mm.
The rotation shaft is rotatably supported by the image carrier unit cover 24. Then, on the periphery of the image carrier 24a,
A cleaner 24c and a primary charging unit 24d are provided.

By transmitting the driving force of a driving motor (not shown) to one end of the rotating shaft of the image carrier 24a,
The image carrier 24a is rotated in the direction of the arrow in FIG. 6 according to the image forming operation. The image carrier unit is detachable from the apparatus main body 29, and can be easily replaced in accordance with the life of the image carrier 24a.

"Charging means" The primary charging means 24b includes:
The method uses a so-called contact charging method as disclosed in JP-A-63-149669, in which a conductive roller is brought into contact with an image carrier 24a, and a voltage is applied to the conductive roller. This is to uniformly charge the surface of 24a.

"Cleaning means" Cleaning means 2
Reference numeral 4 denotes a unit for cleaning the toner remaining on the image carrier 24a after the toner visualized on the image carrier 24a by the developing unit 100 is transferred to the transfer material 22. The cleaning means 24 includes a waste toner conveying screw 24d passed through a waste toner container.
Sends the residual toner to a waste toner container attached to the side of the main body. When the waste toner container is full of waste toner, the waste toner container is removed and replaced with a new one.

"Developing Means" The developing means 100 includes four developing means 100 for developing each of magenta, cyan, yellow and black in order to visualize the electrostatic latent image formed on the image carrier 24a. Developing cartridges 100M, 100C,
100Y and 100K are provided.

The four developing cartridges 100M, 1
00C, 100Y, and 100K are arranged so as to be rotatable about a shaft 14.
Since the centers of 100C, 100Y, and 100K rotate in conjunction with the rotation gears arranged on the outer periphery of the revolving gear, their postures are always kept constant.

When forming an image, developing cartridges 100M, 100C, 100Y, and 100K corresponding to magenta, cyan, yellow, and black color development, respectively.
Rotates around the shaft 14, the predetermined developing cartridges (100M, 100C, 100Y, 100K) stop at the position facing the image carrier unit, and the developing roller 3 moves at a minute interval (300 μm) with respect to the image carrier 24a. ), The image carrier 24a
Then, visible images are sequentially formed by the respective color toners.

That is, the toner in the container corresponding to the color to be developed is sent to the application roller 5 by the feeding mechanism, and a thin layer of the toner is applied to the outer periphery of the rotating application roller 5 and the rotating developing roller 3 by the blade 4. Charge (frictional electrification). Then, by applying a developing bias between the developing roller 3 and the image carrier 24a on which the latent image is formed, the electrostatic latent image on the image carrier 24a is developed with toner according to the latent image.

Each of the developing cartridges 100M, 100M
When the developing cartridges 100M, 100C, 100Y, and 100K are rotated to the developing positions, the developing rollers 3 of C, 100Y, and 100K are electrically connected to a high-voltage power supply for developing each color provided in the apparatus main body 29, and A voltage is selectively applied for each development.

"Fixing Section" The fixing section 26 is provided with a transfer drum 23.
The image forming apparatus 100 fixes an image formed by the developing unit 100 on the transfer material 22 wound around the recording medium 22. The image forming apparatus includes a driving roller 26a that is driven to rotate and a fixing roller 26b that is pressed against the driving roller 26a and applies heat and pressure to the transfer material 22. I have. That is, the transfer material 22 peeled off from the transfer drum 23 is
The toner image is fixed by being conveyed by the driving roller 26a when passing through the fixing roller 26a and applying heat and pressure by the fixing roller 26b.

The cleaning member 26c is in contact with the fixing roller 26b, and the toner adhered to the fixing roller 26b is removed by the cleaning member 26c.

"Image Forming Operation" Next, an image forming operation of the laser beam printer having the above-described configuration will be described.

First, the feed roller 21b shown in FIG. 6 is driven to rotate to separate one transfer material 22 in the paper feed cassette 21a, and the transfer material 22 is fed to the transfer drum 23. The transfer drum 23 rotates in the direction of the arrow in FIG. 6 to grip the leading end of the fed transfer material 22 with a gripper 23f, and electrostatically attracts the transfer material 22 to its peripheral surface.

Further, in synchronization with the rotation of the transfer drum 23, the image carrier 24a is rotated in the direction of the arrow in FIG.
The surface of the image carrier 24a is uniformly charged by b, and the scanner unit 30 irradiates a magenta image with light to form a magenta latent image on the image carrier 24a. Simultaneously with the formation of the latent image, the magenta developing unit 100M is driven, and a voltage having substantially the same potential as the charging polarity of the image carrier 24 is applied so that magenta toner adheres to the latent image on the image carrier 24a. Magenta development is performed, and a voltage having a characteristic opposite to that of the toner is applied to the transfer roller 3 to transfer the toner on the image carrier 24 a to the transfer material 22 on the transfer drum 23.

When the transfer of the magenta toner onto the transfer material 22 is completed through the above-described process, the next developing unit 100C is rotated and positioned at a position facing the image carrier 24a, and the cyan developer is moved in the same manner as magenta. Latent image formation and toner transfer are performed, and thereafter, yellow and black latent images and toner transfer are sequentially performed in the same manner to form a color image on the transfer material 22.

After the color image is formed, the transfer material 22 is separated from the transfer drum 23 and is conveyed to the fixing unit 26. After the toner is fixed in the fixing unit 26, the transfer material 22 is discharged by the discharge roller pair 27. After discharging to the tray 28, a series of image formation is completed.

Next, a developing cartridge switching mechanism (hereinafter referred to as a developing switching mechanism), which is a feature of the present invention, will be described in detail with reference to FIGS. FIG. 1 is a front view of the development switching mechanism, and FIG. 2 is a partial perspective view of the development switching mechanism.

The developing switching mechanism holds the four developing cartridges 100M, 100C, 100Y and 100K in a detachable manner and is rotatable about a shaft 14. The rotation is performed by a cartridge selecting motor (not shown) shown in FIG. Performed in the direction of the arrow.

A stop position flag 1 is provided for the development switching mechanism.
M, 1C, 1Y, and 1K are provided, and only the stop position flag 1M is longer than the other stop position flags 1C, 1Y, and 1K to take the reference of the rotation phase.

On the other hand, a revolution position sensor 2 is provided on the apparatus main body side. This revolution position sensor 2 is shown in FIG.
As shown in the figure, the LED light from the light emitting unit 2a is
It is composed of a general photo sensor that detects with.

After the development switching mechanism is rotated and the stop position flag 1M passes through the revolution position sensor 2, the motor rotates for a time determined according to the color, and the developing cartridges 100M and 100M of the respective colors are rotated. 100C, 100Y,
100K are sequentially stopped at a position facing the image carrier 24a. Developing cartridges 100M, 100C, 100
After Y and 100K stop, each developing cartridge 100
M, 100C, 100Y, and 100K are sequentially pressed and contacted toward the image carrier 24a to perform predetermined development.

For example, when developing a cyan latent image,
After the stop position flag 1M is detected, the motor rotates and stops for a predetermined period of time. At that time, if the stop position flap 1C cuts off the revolution position sensor 2 within a predetermined time, a normal display is output. If the revolution position sensor 2 is not turned on due to a motor step-out or gear tooth skipping, an error display is output. . As described above, the revolving position sensor 2 determines the positions of the developing cartridges 100M, 100C, 100Y, and 100K and detects a malfunction of the developing switching mechanism.

Incidentally, the stop position flags 1M, 1C, 1
In Y and 1K, a surface having a certain angle with respect to the flag locus circle 10 is formed. This surface is formed so that the distance from the rotation center 14 increases as the position moves downstream in the flag traveling direction. Then, the stop position flags 1M, 1
C, 1Y, and 1K generate air when the development switching mechanism rotates, so that a surface having an angle with respect to the traveling direction receives air resistance, and tries to push air near the surface to the outside of the locus circle 10. Thereby, the ratio of the scattered toner drifting around the revolution position sensor 2 is reduced.

Further, the stop position flags 1M, 1C, 1Y, 1 at the time of development shown in FIG. 1 (that is, when the development switching mechanism is stopped).
With respect to the positional relationship between K and the revolution position sensor 2, the stop position flag 1 is set so as to protect the sensor light emitting portion 2a with respect to the image bearing member 24a and the developing roller 5 where development is being performed.
M, 1C, 1Y, and 1K are located. The stop position flags 1M, 1C, 1Y, and 1K are all the same, and the stop position flags 1M, 1C, 1Y, and 1K are always provided between the image carrier 24a and the light emitting unit 2a of the revolving position sensor 2 during development. 2b.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. 3 is a front view of the development switching mechanism according to the present embodiment, FIG. 4 is a side view of the development switching mechanism, and FIG. 5 is a partial perspective view of the development switching mechanism.

This embodiment is characterized in that a plurality of rib-like projections serving as fins are provided in addition to the flag in order to strongly generate the wind in the first embodiment.

In this embodiment, as shown in FIG. 3, the stop position flags 1M, 1C, 1Y, 1K and the plurality of rib-like projections 6 are integrally formed on the developing cartridge support plate 7. A gear 7a is formed on the outer periphery of the developing cartridge supporting plate 7, and the developing cartridge supporting plate 7
Is driven by a driving motor (not shown) to rotate the developing switching mechanism.

The rib-like projections 6 are provided at six positions on the developing cartridge support plate 7 and are formed radially from a shaft 14 which is the center of rotation of the developing switching mechanism. The rib 6 does not extend linearly from the shaft 14 toward the outer periphery, but has a certain angle with respect to the radiation, so that wind can be positively generated outside the development switching mechanism. .

FIG. 4 is a side view of the developing switching mechanism in a state where the developing cartridge is not mounted. As shown in FIG. 4, the developing switching mechanism mainly serves as a threshold between the developing cartridge support plate 7 and each developing cartridge. It is constituted by four stays 8 which also serve as a support, and is rotatably supported by the main body side plate 9.

The revolution position sensor 2 is connected to the main body side plate 9.
Are fixed via sheet metal (not shown). The rib-like projection 6 is formed so as to fill a space between the main body side plate 9 and the development switching mechanism and the revolution position sensor 2. Note that, in the present embodiment, the rib-shaped projection 6 is provided with the stop position flag 1M,
Although it is lower than 1C, 1Y, and 1K (lower in the longitudinal direction of FIG. 4), it is better to make the height of the rib-like projections 6 as high as possible to generate strong wind.

When the developing switching mechanism rotates, the rib-like projections 6 function as fins, and the space between the developing cartridge supporting plate 7 and the main body side plate 9 is directed toward the outer periphery of the developing switching mechanism as indicated by an arrow in FIG. Wind flow to the wind occurs. And
The flow of the wind prevents the scattered toner from approaching the periphery of the revolution position sensor 2.

[0052]

As is apparent from the above description, claim 1
According to the invention described above, since the flag is formed on a surface having a certain angle with respect to the flag locus, it is difficult for the scattered toner to approach the periphery of the optical detection means, and the scattered toner once attached to the optical detection means is blown off. Can be.
Further, when the developing cartridge switching mechanism is stopped, the flag is formed at a position that shields the image carrier and the optical detecting means, so that the toner scattered to the optical detecting means immediately after the developing cartridge switching mechanism is stopped. Adhesion can be prevented beforehand, and stable operation of the developing cartridge switching mechanism can be ensured.

According to the second aspect of the present invention, since a plurality of rib-like projections are formed on the same plane on which the flag is formed in a substantially radial shape from the rotation center of the developing cartridge switching mechanism, a strong wind around the optical detecting means is provided. Is generated, and the adhesion of the scattered toner to the optical detection means is more effectively prevented by the flow of the wind.

[Brief description of the drawings]

FIG. 1 is a front view of a development switching mechanism of a multicolor image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a partial perspective view of a development switching mechanism of the multicolor image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a front view of a development switching mechanism of the multicolor image forming apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a side view of a development switching mechanism of the multicolor image forming apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a partial perspective view of a development switching mechanism of the multicolor image forming apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a sectional view of a multicolor image forming apparatus (laser beam printer) according to the present invention.

[Explanation of symbols]

1M, 1C, 1Y, 1K Stop position flag (flag) 2 Revolution position sensor (optical detection means) 6 Rib-shaped protrusion 7 Developing cartridge support plate 10 Flag locus circle (flag locus) 24a Image carrier 100 Developing means 100M, 100C 100Y, 100K developing cartridge

Claims (2)

[Claims] A developing cartridge switching mechanism for mounting a plurality of detachable developing cartridges, having a flag corresponding to each developing cartridge, and rotating and moving the developing cartridge to a position facing the image carrier; The developing cartridge is sequentially selected and switched by detecting the flag with the optical detecting means disposed on the mounting body,
In a multicolor image forming apparatus for forming a multicolor image by forming a multicolor image through a plurality of development processes, forming the flag on a surface having a certain angle with respect to a flag locus, A multicolor image forming apparatus, wherein the flag is formed at a position that shields the image carrier and the optical detection means when the cartridge switching mechanism is stopped. 2. The multicolor image forming apparatus according to claim 1, wherein a plurality of rib-shaped projections are formed on the same plane on which the flag is formed in a substantially radial shape from a rotation center of the developing cartridge switching mechanism. apparatus.